2. Built-in Functions
*********************

The Python interpreter has a number of functions and types built into
it that are always available.  They are listed here in alphabetical
order.

+---------------------+-------------------+--------------------+------------------+----------------------+
|                     |                   | Built-in Functions |                  |                      |
+=====================+===================+====================+==================+======================+
| "abs()"             | "dict()"          | "help()"           | "min()"          | "setattr()"          |
+---------------------+-------------------+--------------------+------------------+----------------------+
| "all()"             | "dir()"           | "hex()"            | "next()"         | "slice()"            |
+---------------------+-------------------+--------------------+------------------+----------------------+
| "any()"             | "divmod()"        | "id()"             | "object()"       | "sorted()"           |
+---------------------+-------------------+--------------------+------------------+----------------------+
| "ascii()"           | "enumerate()"     | "input()"          | "oct()"          | "staticmethod()"     |
+---------------------+-------------------+--------------------+------------------+----------------------+
| "bin()"             | "eval()"          | "int()"            | "open()"         | "str()"              |
+---------------------+-------------------+--------------------+------------------+----------------------+
| "bool()"            | "exec()"          | "isinstance()"     | "ord()"          | "sum()"              |
+---------------------+-------------------+--------------------+------------------+----------------------+
| "bytearray()"       | "filter()"        | "issubclass()"     | "pow()"          | "super()"            |
+---------------------+-------------------+--------------------+------------------+----------------------+
| "bytes()"           | "float()"         | "iter()"           | "print()"        | "tuple()"            |
+---------------------+-------------------+--------------------+------------------+----------------------+
| "callable()"        | "format()"        | "len()"            | "property()"     | "type()"             |
+---------------------+-------------------+--------------------+------------------+----------------------+
| "chr()"             | "frozenset()"     | "list()"           | "range()"        | "vars()"             |
+---------------------+-------------------+--------------------+------------------+----------------------+
| "classmethod()"     | "getattr()"       | "locals()"         | "repr()"         | "zip()"              |
+---------------------+-------------------+--------------------+------------------+----------------------+
| "compile()"         | "globals()"       | "map()"            | "reversed()"     | "__import__()"       |
+---------------------+-------------------+--------------------+------------------+----------------------+
| "complex()"         | "hasattr()"       | "max()"            | "round()"        |                      |
+---------------------+-------------------+--------------------+------------------+----------------------+
| "delattr()"         | "hash()"          | "memoryview()"     | "set()"          |                      |
+---------------------+-------------------+--------------------+------------------+----------------------+

abs(x)

   Return the absolute value of a number.  The argument may be an
   integer or a floating point number.  If the argument is a complex
   number, its magnitude is returned.

all(iterable)

   Return "True" if all elements of the *iterable* are true (or if the
   iterable is empty).  Equivalent to:

      def all(iterable):
          for element in iterable:
              if not element:
                  return False
          return True

any(iterable)

   Return "True" if any element of the *iterable* is true.  If the
   iterable is empty, return "False".  Equivalent to:

      def any(iterable):
          for element in iterable:
              if element:
                  return True
          return False

ascii(object)

   As "repr()", return a string containing a printable representation
   of an object, but escape the non-ASCII characters in the string
   returned by "repr()" using "\x", "\u" or "\U" escapes.  This
   generates a string similar to that returned by "repr()" in Python
   2.

bin(x)

   Convert an integer number to a binary string. The result is a valid
   Python expression.  If *x* is not a Python "int" object, it has to
   define an "__index__()" method that returns an integer.

class bool([x])

   Return a Boolean value, i.e. one of "True" or "False".  *x* is
   converted using the standard truth testing procedure.  If *x* is
   false or omitted, this returns "False"; otherwise it returns
   "True".  The "bool" class is a subclass of "int" (see Numeric Types
   — int, float, complex). It cannot be subclassed further.  Its only
   instances are "False" and "True" (see Boolean Values).

class bytearray([source[, encoding[, errors]]])

   Return a new array of bytes.  The "bytearray" class is a mutable
   sequence of integers in the range 0 <= x < 256.  It has most of the
   usual methods of mutable sequences, described in Mutable Sequence
   Types, as well as most methods that the "bytes" type has, see Bytes
   and Bytearray Operations.

   The optional *source* parameter can be used to initialize the array
   in a few different ways:

   * If it is a *string*, you must also give the *encoding* (and
     optionally, *errors*) parameters; "bytearray()" then converts the
     string to bytes using "str.encode()".

   * If it is an *integer*, the array will have that size and will
     be initialized with null bytes.

   * If it is an object conforming to the *buffer* interface, a
     read- only buffer of the object will be used to initialize the
     bytes array.

   * If it is an *iterable*, it must be an iterable of integers in
     the range "0 <= x < 256", which are used as the initial contents
     of the array.

   Without an argument, an array of size 0 is created.

   See also Binary Sequence Types — bytes, bytearray, memoryview and
   Bytearray Objects.

class bytes([source[, encoding[, errors]]])

   Return a new “bytes” object, which is an immutable sequence of
   integers in the range "0 <= x < 256".  "bytes" is an immutable
   version of "bytearray" – it has the same non-mutating methods and
   the same indexing and slicing behavior.

   Accordingly, constructor arguments are interpreted as for
   "bytearray()".

   Bytes objects can also be created with literals, see String and
   Bytes literals.

   See also Binary Sequence Types — bytes, bytearray, memoryview,
   Bytes, and Bytes and Bytearray Operations.

callable(object)

   Return "True" if the *object* argument appears callable, "False" if
   not.  If this returns true, it is still possible that a call fails,
   but if it is false, calling *object* will never succeed. Note that
   classes are callable (calling a class returns a new instance);
   instances are callable if their class has a "__call__()" method.

   New in version 3.2: This function was first removed in Python 3.0
   and then brought back in Python 3.2.

chr(i)

   Return the string representing a character whose Unicode code point
   is the integer *i*.  For example, "chr(97)" returns the string
   "'a'", while "chr(8364)" returns the string "'€'". This is the
   inverse of "ord()".

   The valid range for the argument is from 0 through 1,114,111
   (0x10FFFF in base 16).  "ValueError" will be raised if *i* is
   outside that range.

classmethod(function)

   Return a class method for *function*.

   A class method receives the class as implicit first argument, just
   like an instance method receives the instance. To declare a class
   method, use this idiom:

      class C:
          @classmethod
          def f(cls, arg1, arg2, ...): ...

   The "@classmethod" form is a function *decorator* – see the
   description of function definitions in Function definitions for
   details.

   It can be called either on the class (such as "C.f()") or on an
   instance (such as "C().f()").  The instance is ignored except for
   its class. If a class method is called for a derived class, the
   derived class object is passed as the implied first argument.

   Class methods are different than C++ or Java static methods. If you
   want those, see "staticmethod()" in this section.

   For more information on class methods, consult the documentation on
   the standard type hierarchy in The standard type hierarchy.

compile(source, filename, mode, flags=0, dont_inherit=False, optimize=-1)

   Compile the *source* into a code or AST object.  Code objects can
   be executed by "exec()" or "eval()".  *source* can either be a
   normal string, a byte string, or an AST object.  Refer to the "ast"
   module documentation for information on how to work with AST
   objects.

   The *filename* argument should give the file from which the code
   was read; pass some recognizable value if it wasn’t read from a
   file ("'<string>'" is commonly used).

   The *mode* argument specifies what kind of code must be compiled;
   it can be "'exec'" if *source* consists of a sequence of
   statements, "'eval'" if it consists of a single expression, or
   "'single'" if it consists of a single interactive statement (in the
   latter case, expression statements that evaluate to something other
   than "None" will be printed).

   The optional arguments *flags* and *dont_inherit* control which
   future statements (see **PEP 236**) affect the compilation of
   *source*.  If neither is present (or both are zero) the code is
   compiled with those future statements that are in effect in the
   code that is calling "compile()".  If the *flags* argument is given
   and *dont_inherit* is not (or is zero) then the future statements
   specified by the *flags* argument are used in addition to those
   that would be used anyway. If *dont_inherit* is a non-zero integer
   then the *flags* argument is it – the future statements in effect
   around the call to compile are ignored.

   Future statements are specified by bits which can be bitwise ORed
   together to specify multiple statements.  The bitfield required to
   specify a given feature can be found as the "compiler_flag"
   attribute on the "_Feature" instance in the "__future__" module.

   The argument *optimize* specifies the optimization level of the
   compiler; the default value of "-1" selects the optimization level
   of the interpreter as given by "-O" options.  Explicit levels are
   "0" (no optimization; "__debug__" is true), "1" (asserts are
   removed, "__debug__" is false) or "2" (docstrings are removed too).

   This function raises "SyntaxError" if the compiled source is
   invalid, and "ValueError" if the source contains null bytes.

   If you want to parse Python code into its AST representation, see
   "ast.parse()".

   Note: When compiling a string with multi-line code in "'single'"
     or "'eval'" mode, input must be terminated by at least one
     newline character.  This is to facilitate detection of incomplete
     and complete statements in the "code" module.

   Changed in version 3.2: Allowed use of Windows and Mac newlines.
   Also input in "'exec'" mode does not have to end in a newline
   anymore.  Added the *optimize* parameter.

   Changed in version 3.5: Previously, "TypeError" was raised when
   null bytes were encountered in *source*.

class complex([real[, imag]])

   Return a complex number with the value *real* + *imag**1j or
   convert a string or number to a complex number.  If the first
   parameter is a string, it will be interpreted as a complex number
   and the function must be called without a second parameter.  The
   second parameter can never be a string. Each argument may be any
   numeric type (including complex).  If *imag* is omitted, it
   defaults to zero and the constructor serves as a numeric conversion
   like "int" and "float".  If both arguments are omitted, returns
   "0j".

   Note: When converting from a string, the string must not contain
     whitespace around the central "+" or "-" operator.  For example,
     "complex('1+2j')" is fine, but "complex('1 + 2j')" raises
     "ValueError".

   The complex type is described in Numeric Types — int, float,
   complex.

delattr(object, name)

   This is a relative of "setattr()".  The arguments are an object and
   a string.  The string must be the name of one of the object’s
   attributes.  The function deletes the named attribute, provided the
   object allows it.  For example, "delattr(x, 'foobar')" is
   equivalent to "del x.foobar".

class dict(**kwarg)
class dict(mapping, **kwarg)
class dict(iterable, **kwarg)

   Create a new dictionary.  The "dict" object is the dictionary
   class. See "dict" and Mapping Types — dict for documentation about
   this class.

   For other containers see the built-in "list", "set", and "tuple"
   classes, as well as the "collections" module.

dir([object])

   Without arguments, return the list of names in the current local
   scope.  With an argument, attempt to return a list of valid
   attributes for that object.

   If the object has a method named "__dir__()", this method will be
   called and must return the list of attributes. This allows objects
   that implement a custom "__getattr__()" or "__getattribute__()"
   function to customize the way "dir()" reports their attributes.

   If the object does not provide "__dir__()", the function tries its
   best to gather information from the object’s "__dict__" attribute,
   if defined, and from its type object.  The resulting list is not
   necessarily complete, and may be inaccurate when the object has a
   custom "__getattr__()".

   The default "dir()" mechanism behaves differently with different
   types of objects, as it attempts to produce the most relevant,
   rather than complete, information:

   * If the object is a module object, the list contains the names
     of the module’s attributes.

   * If the object is a type or class object, the list contains the
     names of its attributes, and recursively of the attributes of its
     bases.

   * Otherwise, the list contains the object’s attributes’ names,
     the names of its class’s attributes, and recursively of the
     attributes of its class’s base classes.

   The resulting list is sorted alphabetically.  For example:

   >>> import struct
   >>> dir()   # show the names in the module namespace
   ['__builtins__', '__name__', 'struct']
   >>> dir(struct)   # show the names in the struct module # doctest: +SKIP
   ['Struct', '__all__', '__builtins__', '__cached__', '__doc__', '__file__',
    '__initializing__', '__loader__', '__name__', '__package__',
    '_clearcache', 'calcsize', 'error', 'pack', 'pack_into',
    'unpack', 'unpack_from']
   >>> class Shape:
   ...     def __dir__(self):
   ...         return ['area', 'perimeter', 'location']
   >>> s = Shape()
   >>> dir(s)
   ['area', 'location', 'perimeter']

   Note: Because "dir()" is supplied primarily as a convenience for
     use at an interactive prompt, it tries to supply an interesting
     set of names more than it tries to supply a rigorously or
     consistently defined set of names, and its detailed behavior may
     change across releases.  For example, metaclass attributes are
     not in the result list when the argument is a class.

divmod(a, b)

   Take two (non complex) numbers as arguments and return a pair of
   numbers consisting of their quotient and remainder when using
   integer division.  With mixed operand types, the rules for binary
   arithmetic operators apply.  For integers, the result is the same
   as "(a // b, a % b)". For floating point numbers the result is "(q,
   a % b)", where *q* is usually "math.floor(a / b)" but may be 1 less
   than that.  In any case "q * b + a % b" is very close to *a*, if "a
   % b" is non-zero it has the same sign as *b*, and "0 <= abs(a % b)
   < abs(b)".

enumerate(iterable, start=0)

   Return an enumerate object. *iterable* must be a sequence, an
   *iterator*, or some other object which supports iteration. The
   "__next__()" method of the iterator returned by "enumerate()"
   returns a tuple containing a count (from *start* which defaults to
   0) and the values obtained from iterating over *iterable*.

   >>> seasons = ['Spring', 'Summer', 'Fall', 'Winter']
   >>> list(enumerate(seasons))
   [(0, 'Spring'), (1, 'Summer'), (2, 'Fall'), (3, 'Winter')]
   >>> list(enumerate(seasons, start=1))
   [(1, 'Spring'), (2, 'Summer'), (3, 'Fall'), (4, 'Winter')]

   Equivalent to:

      def enumerate(sequence, start=0):
          n = start
          for elem in sequence:
              yield n, elem
              n += 1

eval(expression, globals=None, locals=None)

   The arguments are a string and optional globals and locals.  If
   provided, *globals* must be a dictionary.  If provided, *locals*
   can be any mapping object.

   The *expression* argument is parsed and evaluated as a Python
   expression (technically speaking, a condition list) using the
   *globals* and *locals* dictionaries as global and local namespace.
   If the *globals* dictionary is present and lacks ‘__builtins__’,
   the current globals are copied into *globals* before *expression*
   is parsed.  This means that *expression* normally has full access
   to the standard "builtins" module and restricted environments are
   propagated.  If the *locals* dictionary is omitted it defaults to
   the *globals* dictionary.  If both dictionaries are omitted, the
   expression is executed in the environment where "eval()" is called.
   The return value is the result of the evaluated expression. Syntax
   errors are reported as exceptions.  Example:

   >>> x = 1
   >>> eval('x+1')
   2

   This function can also be used to execute arbitrary code objects
   (such as those created by "compile()").  In this case pass a code
   object instead of a string.  If the code object has been compiled
   with "'exec'" as the *mode* argument, "eval()"’s return value will
   be "None".

   Hints: dynamic execution of statements is supported by the "exec()"
   function.  The "globals()" and "locals()" functions returns the
   current global and local dictionary, respectively, which may be
   useful to pass around for use by "eval()" or "exec()".

   See "ast.literal_eval()" for a function that can safely evaluate
   strings with expressions containing only literals.

exec(object[, globals[, locals]])

   This function supports dynamic execution of Python code. *object*
   must be either a string or a code object.  If it is a string, the
   string is parsed as a suite of Python statements which is then
   executed (unless a syntax error occurs). [1] If it is a code
   object, it is simply executed.  In all cases, the code that’s
   executed is expected to be valid as file input (see the section
   “File input” in the Reference Manual). Be aware that the "return"
   and "yield" statements may not be used outside of function
   definitions even within the context of code passed to the "exec()"
   function. The return value is "None".

   In all cases, if the optional parts are omitted, the code is
   executed in the current scope.  If only *globals* is provided, it
   must be a dictionary, which will be used for both the global and
   the local variables.  If *globals* and *locals* are given, they are
   used for the global and local variables, respectively.  If
   provided, *locals* can be any mapping object.  Remember that at
   module level, globals and locals are the same dictionary. If exec
   gets two separate objects as *globals* and *locals*, the code will
   be executed as if it were embedded in a class definition.

   If the *globals* dictionary does not contain a value for the key
   "__builtins__", a reference to the dictionary of the built-in
   module "builtins" is inserted under that key.  That way you can
   control what builtins are available to the executed code by
   inserting your own "__builtins__" dictionary into *globals* before
   passing it to "exec()".

   Note: The built-in functions "globals()" and "locals()" return
     the current global and local dictionary, respectively, which may
     be useful to pass around for use as the second and third argument
     to "exec()".

   Note: The default *locals* act as described for function
     "locals()" below: modifications to the default *locals*
     dictionary should not be attempted. Pass an explicit *locals*
     dictionary if you need to see effects of the code on *locals*
     after function "exec()" returns.

filter(function, iterable)

   Construct an iterator from those elements of *iterable* for which
   *function* returns true.  *iterable* may be either a sequence, a
   container which supports iteration, or an iterator.  If *function*
   is "None", the identity function is assumed, that is, all elements
   of *iterable* that are false are removed.

   Note that "filter(function, iterable)" is equivalent to the
   generator expression "(item for item in iterable if
   function(item))" if function is not "None" and "(item for item in
   iterable if item)" if function is "None".

   See "itertools.filterfalse()" for the complementary function that
   returns elements of *iterable* for which *function* returns false.

class float([x])

   Return a floating point number constructed from a number or string
   *x*.

   If the argument is a string, it should contain a decimal number,
   optionally preceded by a sign, and optionally embedded in
   whitespace.  The optional sign may be "'+'" or "'-'"; a "'+'" sign
   has no effect on the value produced.  The argument may also be a
   string representing a NaN (not-a-number), or a positive or negative
   infinity.  More precisely, the input must conform to the following
   grammar after leading and trailing whitespace characters are
   removed:

      sign           ::= "+" | "-"
      infinity       ::= "Infinity" | "inf"
      nan            ::= "nan"
      numeric_value  ::= floatnumber | infinity | nan
      numeric_string ::= [sign] numeric_value

   Here "floatnumber" is the form of a Python floating-point literal,
   described in Floating point literals.  Case is not significant, so,
   for example, “inf”, “Inf”, “INFINITY” and “iNfINity” are all
   acceptable spellings for positive infinity.

   Otherwise, if the argument is an integer or a floating point
   number, a floating point number with the same value (within
   Python’s floating point precision) is returned.  If the argument is
   outside the range of a Python float, an "OverflowError" will be
   raised.

   For a general Python object "x", "float(x)" delegates to
   "x.__float__()".

   If no argument is given, "0.0" is returned.

   Examples:

      >>> float('+1.23')
      1.23
      >>> float('   -12345\n')
      -12345.0
      >>> float('1e-003')
      0.001
      >>> float('+1E6')
      1000000.0
      >>> float('-Infinity')
      -inf

   The float type is described in Numeric Types — int, float, complex.

format(value[, format_spec])

   Convert a *value* to a “formatted” representation, as controlled by
   *format_spec*.  The interpretation of *format_spec* will depend on
   the type of the *value* argument, however there is a standard
   formatting syntax that is used by most built-in types: Format
   Specification Mini-Language.

   The default *format_spec* is an empty string which usually gives
   the same effect as calling "str(value)".

   A call to "format(value, format_spec)" is translated to
   "type(value).__format__(value, format_spec)" which bypasses the
   instance dictionary when searching for the value’s "__format__()"
   method.  A "TypeError" exception is raised if the method search
   reaches "object" and the *format_spec* is non-empty, or if either
   the *format_spec* or the return value are not strings.

   Changed in version 3.4: "object().__format__(format_spec)" raises
   "TypeError" if *format_spec* is not an empty string.

class frozenset([iterable])

   Return a new "frozenset" object, optionally with elements taken
   from *iterable*.  "frozenset" is a built-in class.  See "frozenset"
   and Set Types — set, frozenset for documentation about this class.

   For other containers see the built-in "set", "list", "tuple", and
   "dict" classes, as well as the "collections" module.

getattr(object, name[, default])

   Return the value of the named attribute of *object*.  *name* must
   be a string. If the string is the name of one of the object’s
   attributes, the result is the value of that attribute.  For
   example, "getattr(x, 'foobar')" is equivalent to "x.foobar".  If
   the named attribute does not exist, *default* is returned if
   provided, otherwise "AttributeError" is raised.

globals()

   Return a dictionary representing the current global symbol table.
   This is always the dictionary of the current module (inside a
   function or method, this is the module where it is defined, not the
   module from which it is called).

hasattr(object, name)

   The arguments are an object and a string.  The result is "True" if
   the string is the name of one of the object’s attributes, "False"
   if not. (This is implemented by calling "getattr(object, name)" and
   seeing whether it raises an "AttributeError" or not.)

hash(object)

      Return the hash value of the object (if it has one).  Hash
      values are integers.  They are used to quickly compare
      dictionary keys during a dictionary lookup.  Numeric values that
      compare equal have the same hash value (even if they are of
      different types, as is the case for 1 and 1.0).

   Note: For objects with custom "__hash__()" methods, note that
     "hash()" truncates the return value based on the bit width of the
     host machine. See "__hash__()" for details.

help([object])

   Invoke the built-in help system.  (This function is intended for
   interactive use.)  If no argument is given, the interactive help
   system starts on the interpreter console.  If the argument is a
   string, then the string is looked up as the name of a module,
   function, class, method, keyword, or documentation topic, and a
   help page is printed on the console.  If the argument is any other
   kind of object, a help page on the object is generated.

   This function is added to the built-in namespace by the "site"
   module.

   Changed in version 3.4: Changes to "pydoc" and "inspect" mean that
   the reported signatures for callables are now more comprehensive
   and consistent.

hex(x)

   Convert an integer number to a lowercase hexadecimal string
   prefixed with “0x”, for example:

   >>> hex(255)
   '0xff'
   >>> hex(-42)
   '-0x2a'

   If x is not a Python "int" object, it has to define an __index__()
   method that returns an integer.

   See also "int()" for converting a hexadecimal string to an integer
   using a base of 16.

   Note: To obtain a hexadecimal string representation for a float,
     use the "float.hex()" method.

id(object)

   Return the “identity” of an object.  This is an integer which is
   guaranteed to be unique and constant for this object during its
   lifetime. Two objects with non-overlapping lifetimes may have the
   same "id()" value.

   **CPython implementation detail:** This is the address of the
   object in memory.

input([prompt])

   If the *prompt* argument is present, it is written to standard
   output without a trailing newline.  The function then reads a line
   from input, converts it to a string (stripping a trailing newline),
   and returns that.  When EOF is read, "EOFError" is raised.
   Example:

      >>> s = input('--> ')  # doctest: +SKIP
      --> Monty Python's Flying Circus
      >>> s  # doctest: +SKIP
      "Monty Python's Flying Circus"

   If the "readline" module was loaded, then "input()" will use it to
   provide elaborate line editing and history features.

class int(x=0)
class int(x, base=10)

   Return an integer object constructed from a number or string *x*,
   or return "0" if no arguments are given.  If *x* is a number,
   return "x.__int__()".  For floating point numbers, this truncates
   towards zero.

   If *x* is not a number or if *base* is given, then *x* must be a
   string, "bytes", or "bytearray" instance representing an integer
   literal in radix *base*.  Optionally, the literal can be preceded
   by "+" or "-" (with no space in between) and surrounded by
   whitespace.  A base-n literal consists of the digits 0 to n-1, with
   "a" to "z" (or "A" to "Z") having values 10 to 35.  The default
   *base* is 10. The allowed values are 0 and 2–36. Base-2, -8, and
   -16 literals can be optionally prefixed with "0b"/"0B", "0o"/"0O",
   or "0x"/"0X", as with integer literals in code.  Base 0 means to
   interpret exactly as a code literal, so that the actual base is 2,
   8, 10, or 16, and so that "int('010', 0)" is not legal, while
   "int('010')" is, as well as "int('010', 8)".

   The integer type is described in Numeric Types — int, float,
   complex.

   Changed in version 3.4: If *base* is not an instance of "int" and
   the *base* object has a "base.__index__" method, that method is
   called to obtain an integer for the base.  Previous versions used
   "base.__int__" instead of "base.__index__".

isinstance(object, classinfo)

   Return true if the *object* argument is an instance of the
   *classinfo* argument, or of a (direct, indirect or *virtual*)
   subclass thereof.  If *object* is not an object of the given type,
   the function always returns false. If *classinfo* is a tuple of
   type objects (or recursively, other such tuples), return true if
   *object* is an instance of any of the types. If *classinfo* is not
   a type or tuple of types and such tuples, a "TypeError" exception
   is raised.

issubclass(class, classinfo)

   Return true if *class* is a subclass (direct, indirect or
   *virtual*) of *classinfo*.  A class is considered a subclass of
   itself. *classinfo* may be a tuple of class objects, in which case
   every entry in *classinfo* will be checked. In any other case, a
   "TypeError" exception is raised.

iter(object[, sentinel])

   Return an *iterator* object.  The first argument is interpreted
   very differently depending on the presence of the second argument.
   Without a second argument, *object* must be a collection object
   which supports the iteration protocol (the "__iter__()" method), or
   it must support the sequence protocol (the "__getitem__()" method
   with integer arguments starting at "0").  If it does not support
   either of those protocols, "TypeError" is raised. If the second
   argument, *sentinel*, is given, then *object* must be a callable
   object.  The iterator created in this case will call *object* with
   no arguments for each call to its "__next__()" method; if the value
   returned is equal to *sentinel*, "StopIteration" will be raised,
   otherwise the value will be returned.

   See also Iterator Types.

   One useful application of the second form of "iter()" is to read
   lines of a file until a certain line is reached.  The following
   example reads a file until the "readline()" method returns an empty
   string:

      with open('mydata.txt') as fp:
          for line in iter(fp.readline, ''):
              process_line(line)

len(s)

   Return the length (the number of items) of an object.  The argument
   may be a sequence (such as a string, bytes, tuple, list, or range)
   or a collection (such as a dictionary, set, or frozen set).

class list([iterable])

   Rather than being a function, "list" is actually a mutable sequence
   type, as documented in Lists and Sequence Types — list, tuple,
   range.

locals()

   Update and return a dictionary representing the current local
   symbol table. Free variables are returned by "locals()" when it is
   called in function blocks, but not in class blocks.

   Note: The contents of this dictionary should not be modified;
     changes may not affect the values of local and free variables
     used by the interpreter.

map(function, iterable, ...)

   Return an iterator that applies *function* to every item of
   *iterable*, yielding the results.  If additional *iterable*
   arguments are passed, *function* must take that many arguments and
   is applied to the items from all iterables in parallel.  With
   multiple iterables, the iterator stops when the shortest iterable
   is exhausted.  For cases where the function inputs are already
   arranged into argument tuples, see "itertools.starmap()".

max(iterable, *[, key, default])
max(arg1, arg2, *args[, key])

   Return the largest item in an iterable or the largest of two or
   more arguments.

   If one positional argument is provided, it should be an *iterable*.
   The largest item in the iterable is returned.  If two or more
   positional arguments are provided, the largest of the positional
   arguments is returned.

   There are two optional keyword-only arguments. The *key* argument
   specifies a one-argument ordering function like that used for
   "list.sort()". The *default* argument specifies an object to return
   if the provided iterable is empty. If the iterable is empty and
   *default* is not provided, a "ValueError" is raised.

   If multiple items are maximal, the function returns the first one
   encountered.  This is consistent with other sort-stability
   preserving tools such as "sorted(iterable, key=keyfunc,
   reverse=True)[0]" and "heapq.nlargest(1, iterable, key=keyfunc)".

   New in version 3.4: The *default* keyword-only argument.

memoryview(obj)

   Return a “memory view” object created from the given argument.  See
   Memory Views for more information.

min(iterable, *[, key, default])
min(arg1, arg2, *args[, key])

   Return the smallest item in an iterable or the smallest of two or
   more arguments.

   If one positional argument is provided, it should be an *iterable*.
   The smallest item in the iterable is returned.  If two or more
   positional arguments are provided, the smallest of the positional
   arguments is returned.

   There are two optional keyword-only arguments. The *key* argument
   specifies a one-argument ordering function like that used for
   "list.sort()". The *default* argument specifies an object to return
   if the provided iterable is empty. If the iterable is empty and
   *default* is not provided, a "ValueError" is raised.

   If multiple items are minimal, the function returns the first one
   encountered.  This is consistent with other sort-stability
   preserving tools such as "sorted(iterable, key=keyfunc)[0]" and
   "heapq.nsmallest(1, iterable, key=keyfunc)".

   New in version 3.4: The *default* keyword-only argument.

next(iterator[, default])

   Retrieve the next item from the *iterator* by calling its
   "__next__()" method.  If *default* is given, it is returned if the
   iterator is exhausted, otherwise "StopIteration" is raised.

class object

   Return a new featureless object.  "object" is a base for all
   classes. It has the methods that are common to all instances of
   Python classes.  This function does not accept any arguments.

   Note: "object" does *not* have a "__dict__", so you can’t assign
     arbitrary attributes to an instance of the "object" class.

oct(x)

   Convert an integer number to an octal string.  The result is a
   valid Python expression.  If *x* is not a Python "int" object, it
   has to define an "__index__()" method that returns an integer.

open(file, mode='r', buffering=-1, encoding=None, errors=None, newline=None, closefd=True, opener=None)

   Open *file* and return a corresponding *file object*.  If the file
   cannot be opened, an "OSError" is raised.

   *file* is either a string or bytes object giving the pathname
   (absolute or relative to the current working directory) of the file
   to be opened or an integer file descriptor of the file to be
   wrapped.  (If a file descriptor is given, it is closed when the
   returned I/O object is closed, unless *closefd* is set to "False".)

   *mode* is an optional string that specifies the mode in which the
   file is opened.  It defaults to "'r'" which means open for reading
   in text mode. Other common values are "'w'" for writing (truncating
   the file if it already exists), "'x'" for exclusive creation and
   "'a'" for appending (which on *some* Unix systems, means that *all*
   writes append to the end of the file regardless of the current seek
   position).  In text mode, if *encoding* is not specified the
   encoding used is platform dependent:
   "locale.getpreferredencoding(False)" is called to get the current
   locale encoding. (For reading and writing raw bytes use binary mode
   and leave *encoding* unspecified.)  The available modes are:

   +-----------+-----------------------------------------------------------------+
   | Character | Meaning                                                         |
   +===========+=================================================================+
   | "'r'"     | open for reading (default)                                      |
   +-----------+-----------------------------------------------------------------+
   | "'w'"     | open for writing, truncating the file first                     |
   +-----------+-----------------------------------------------------------------+
   | "'x'"     | open for exclusive creation, failing if the file already exists |
   +-----------+-----------------------------------------------------------------+
   | "'a'"     | open for writing, appending to the end of the file if it exists |
   +-----------+-----------------------------------------------------------------+
   | "'b'"     | binary mode                                                     |
   +-----------+-----------------------------------------------------------------+
   | "'t'"     | text mode (default)                                             |
   +-----------+-----------------------------------------------------------------+
   | "'+'"     | open a disk file for updating (reading and writing)             |
   +-----------+-----------------------------------------------------------------+
   | "'U'"     | *universal newlines* mode (deprecated)                          |
   +-----------+-----------------------------------------------------------------+

   The default mode is "'r'" (open for reading text, synonym of
   "'rt'"). For binary read-write access, the mode "'w+b'" opens and
   truncates the file to 0 bytes.  "'r+b'" opens the file without
   truncation.

   As mentioned in the Overview, Python distinguishes between binary
   and text I/O.  Files opened in binary mode (including "'b'" in the
   *mode* argument) return contents as "bytes" objects without any
   decoding.  In text mode (the default, or when "'t'" is included in
   the *mode* argument), the contents of the file are returned as
   "str", the bytes having been first decoded using a platform-
   dependent encoding or using the specified *encoding* if given.

   Note: Python doesn’t depend on the underlying operating system’s
     notion of text files; all the processing is done by Python
     itself, and is therefore platform-independent.

   *buffering* is an optional integer used to set the buffering
   policy.  Pass 0 to switch buffering off (only allowed in binary
   mode), 1 to select line buffering (only usable in text mode), and
   an integer > 1 to indicate the size in bytes of a fixed-size chunk
   buffer.  When no *buffering* argument is given, the default
   buffering policy works as follows:

   * Binary files are buffered in fixed-size chunks; the size of the
     buffer is chosen using a heuristic trying to determine the
     underlying device’s “block size” and falling back on
     "io.DEFAULT_BUFFER_SIZE".  On many systems, the buffer will
     typically be 4096 or 8192 bytes long.

   * “Interactive” text files (files for which "isatty()" returns
     "True") use line buffering.  Other text files use the policy
     described above for binary files.

   *encoding* is the name of the encoding used to decode or encode the
   file. This should only be used in text mode.  The default encoding
   is platform dependent (whatever "locale.getpreferredencoding()"
   returns), but any *text encoding* supported by Python can be used.
   See the "codecs" module for the list of supported encodings.

   *errors* is an optional string that specifies how encoding and
   decoding errors are to be handled—this cannot be used in binary
   mode. A variety of standard error handlers are available (listed
   under Error Handlers), though any error handling name that has been
   registered with "codecs.register_error()" is also valid.  The
   standard names include:

   * "'strict'" to raise a "ValueError" exception if there is an
     encoding error.  The default value of "None" has the same effect.

   * "'ignore'" ignores errors.  Note that ignoring encoding errors
     can lead to data loss.

   * "'replace'" causes a replacement marker (such as "'?'") to be
     inserted where there is malformed data.

   * "'surrogateescape'" will represent any incorrect bytes as code
     points in the Unicode Private Use Area ranging from U+DC80 to
     U+DCFF.  These private code points will then be turned back into
     the same bytes when the "surrogateescape" error handler is used
     when writing data.  This is useful for processing files in an
     unknown encoding.

   * "'xmlcharrefreplace'" is only supported when writing to a file.
     Characters not supported by the encoding are replaced with the
     appropriate XML character reference "&#nnn;".

   * "'backslashreplace'" replaces malformed data by Python’s
     backslashed escape sequences.

   * "'namereplace'" (also only supported when writing) replaces
     unsupported characters with "\N{...}" escape sequences.

   *newline* controls how *universal newlines* mode works (it only
   applies to text mode).  It can be "None", "''", "'\n'", "'\r'", and
   "'\r\n'".  It works as follows:

   * When reading input from the stream, if *newline* is "None",
     universal newlines mode is enabled.  Lines in the input can end
     in "'\n'", "'\r'", or "'\r\n'", and these are translated into
     "'\n'" before being returned to the caller.  If it is "''",
     universal newlines mode is enabled, but line endings are returned
     to the caller untranslated.  If it has any of the other legal
     values, input lines are only terminated by the given string, and
     the line ending is returned to the caller untranslated.

   * When writing output to the stream, if *newline* is "None", any
     "'\n'" characters written are translated to the system default
     line separator, "os.linesep".  If *newline* is "''" or "'\n'", no
     translation takes place.  If *newline* is any of the other legal
     values, any "'\n'" characters written are translated to the given
     string.

   If *closefd* is "False" and a file descriptor rather than a
   filename was given, the underlying file descriptor will be kept
   open when the file is closed.  If a filename is given *closefd*
   must be "True" (the default) otherwise an error will be raised.

   A custom opener can be used by passing a callable as *opener*. The
   underlying file descriptor for the file object is then obtained by
   calling *opener* with (*file*, *flags*). *opener* must return an
   open file descriptor (passing "os.open" as *opener* results in
   functionality similar to passing "None").

   The newly created file is non-inheritable.

   The following example uses the dir_fd parameter of the "os.open()"
   function to open a file relative to a given directory:

      >>> import os
      >>> dir_fd = os.open('somedir', os.O_RDONLY)
      >>> def opener(path, flags):
      ...     return os.open(path, flags, dir_fd=dir_fd)
      ...
      >>> with open('spamspam.txt', 'w', opener=opener) as f:
      ...     print('This will be written to somedir/spamspam.txt', file=f)
      ...
      >>> os.close(dir_fd)  # don't leak a file descriptor

   The type of *file object* returned by the "open()" function depends
   on the mode.  When "open()" is used to open a file in a text mode
   ("'w'", "'r'", "'wt'", "'rt'", etc.), it returns a subclass of
   "io.TextIOBase" (specifically "io.TextIOWrapper").  When used to
   open a file in a binary mode with buffering, the returned class is
   a subclass of "io.BufferedIOBase".  The exact class varies: in read
   binary mode, it returns an "io.BufferedReader"; in write binary and
   append binary modes, it returns an "io.BufferedWriter", and in
   read/write mode, it returns an "io.BufferedRandom".  When buffering
   is disabled, the raw stream, a subclass of "io.RawIOBase",
   "io.FileIO", is returned.

   See also the file handling modules, such as, "fileinput", "io"
   (where "open()" is declared), "os", "os.path", "tempfile", and
   "shutil".

   Changed in version 3.3: The *opener* parameter was added. The "'x'"
   mode was added. "IOError" used to be raised, it is now an alias of
   "OSError". "FileExistsError" is now raised if the file opened in
   exclusive creation mode ("'x'") already exists.

   Changed in version 3.4: The file is now non-inheritable.

   Deprecated since version 3.4, will be removed in version 4.0: The
   "'U'" mode.

   Changed in version 3.5: If the system call is interrupted and the
   signal handler does not raise an exception, the function now
   retries the system call instead of raising an "InterruptedError"
   exception (see **PEP 475** for the rationale).

   Changed in version 3.5: The "'namereplace'" error handler was
   added.

ord(c)

   Given a string representing one Unicode character, return an
   integer representing the Unicode code point of that character.  For
   example, "ord('a')" returns the integer "97" and "ord('€')" (Euro
   sign) returns "8364".  This is the inverse of "chr()".

pow(x, y[, z])

   Return *x* to the power *y*; if *z* is present, return *x* to the
   power *y*, modulo *z* (computed more efficiently than "pow(x, y) %
   z"). The two-argument form "pow(x, y)" is equivalent to using the
   power operator: "x**y".

   The arguments must have numeric types.  With mixed operand types,
   the coercion rules for binary arithmetic operators apply.  For
   "int" operands, the result has the same type as the operands (after
   coercion) unless the second argument is negative; in that case, all
   arguments are converted to float and a float result is delivered.
   For example, "10**2" returns "100", but "10**-2" returns "0.01".
   If the second argument is negative, the third argument must be
   omitted.  If *z* is present, *x* and *y* must be of integer types,
   and *y* must be non-negative.

print(*objects, sep=' ', end='\n', file=sys.stdout, flush=False)

   Print *objects* to the text stream *file*, separated by *sep* and
   followed by *end*.  *sep*, *end*, *file* and *flush*, if present,
   must be given as keyword arguments.

   All non-keyword arguments are converted to strings like "str()"
   does and written to the stream, separated by *sep* and followed by
   *end*.  Both *sep* and *end* must be strings; they can also be
   "None", which means to use the default values.  If no *objects* are
   given, "print()" will just write *end*.

   The *file* argument must be an object with a "write(string)"
   method; if it is not present or "None", "sys.stdout" will be used.
   Since printed arguments are converted to text strings, "print()"
   cannot be used with binary mode file objects.  For these, use
   "file.write(...)" instead.

   Whether output is buffered is usually determined by *file*, but if
   the *flush* keyword argument is true, the stream is forcibly
   flushed.

   Changed in version 3.3: Added the *flush* keyword argument.

class property(fget=None, fset=None, fdel=None, doc=None)

   Return a property attribute.

   *fget* is a function for getting an attribute value.  *fset* is a
   function for setting an attribute value. *fdel* is a function for
   deleting an attribute value.  And *doc* creates a docstring for the
   attribute.

   A typical use is to define a managed attribute "x":

      class C:
          def __init__(self):
              self._x = None

          def getx(self):
              return self._x

          def setx(self, value):
              self._x = value

          def delx(self):
              del self._x

          x = property(getx, setx, delx, "I'm the 'x' property.")

   If *c* is an instance of *C*, "c.x" will invoke the getter, "c.x =
   value" will invoke the setter and "del c.x" the deleter.

   If given, *doc* will be the docstring of the property attribute.
   Otherwise, the property will copy *fget*’s docstring (if it
   exists).  This makes it possible to create read-only properties
   easily using "property()" as a *decorator*:

      class Parrot:
          def __init__(self):
              self._voltage = 100000

          @property
          def voltage(self):
              """Get the current voltage."""
              return self._voltage

   The "@property" decorator turns the "voltage()" method into a
   “getter” for a read-only attribute with the same name, and it sets
   the docstring for *voltage* to “Get the current voltage.”

   A property object has "getter", "setter", and "deleter" methods
   usable as decorators that create a copy of the property with the
   corresponding accessor function set to the decorated function.
   This is best explained with an example:

      class C:
          def __init__(self):
              self._x = None

          @property
          def x(self):
              """I'm the 'x' property."""
              return self._x

          @x.setter
          def x(self, value):
              self._x = value

          @x.deleter
          def x(self):
              del self._x

   This code is exactly equivalent to the first example.  Be sure to
   give the additional functions the same name as the original
   property ("x" in this case.)

   The returned property object also has the attributes "fget",
   "fset", and "fdel" corresponding to the constructor arguments.

   Changed in version 3.5: The docstrings of property objects are now
   writeable.

range(stop)
range(start, stop[, step])

   Rather than being a function, "range" is actually an immutable
   sequence type, as documented in Ranges and Sequence Types — list,
   tuple, range.

repr(object)

   Return a string containing a printable representation of an object.
   For many types, this function makes an attempt to return a string
   that would yield an object with the same value when passed to
   "eval()", otherwise the representation is a string enclosed in
   angle brackets that contains the name of the type of the object
   together with additional information often including the name and
   address of the object.  A class can control what this function
   returns for its instances by defining a "__repr__()" method.

reversed(seq)

   Return a reverse *iterator*.  *seq* must be an object which has a
   "__reversed__()" method or supports the sequence protocol (the
   "__len__()" method and the "__getitem__()" method with integer
   arguments starting at "0").

round(number[, ndigits])

   Return *number* rounded to *ndigits* precision after the decimal
   point.  If *ndigits* is omitted or is "None", it returns the
   nearest integer to its input.

   For the built-in types supporting "round()", values are rounded to
   the closest multiple of 10 to the power minus *ndigits*; if two
   multiples are equally close, rounding is done toward the even
   choice (so, for example, both "round(0.5)" and "round(-0.5)" are
   "0", and "round(1.5)" is "2").  Any integer value is valid for
   *ndigits* (positive, zero, or negative).  The return value is an
   integer if called with one argument, otherwise of the same type as
   *number*.

   For a general Python object "number", "round(number, ndigits)"
   delegates to "number.__round__(ndigits)".

   Note: The behavior of "round()" for floats can be surprising: for
     example, "round(2.675, 2)" gives "2.67" instead of the expected
     "2.68". This is not a bug: it’s a result of the fact that most
     decimal fractions can’t be represented exactly as a float.  See
     Floating Point Arithmetic:  Issues and Limitations for more
     information.

class set([iterable])

   Return a new "set" object, optionally with elements taken from
   *iterable*.  "set" is a built-in class.  See "set" and Set Types —
   set, frozenset for documentation about this class.

   For other containers see the built-in "frozenset", "list", "tuple",
   and "dict" classes, as well as the "collections" module.

setattr(object, name, value)

   This is the counterpart of "getattr()".  The arguments are an
   object, a string and an arbitrary value.  The string may name an
   existing attribute or a new attribute.  The function assigns the
   value to the attribute, provided the object allows it.  For
   example, "setattr(x, 'foobar', 123)" is equivalent to "x.foobar =
   123".

class slice(stop)
class slice(start, stop[, step])

   Return a *slice* object representing the set of indices specified
   by "range(start, stop, step)".  The *start* and *step* arguments
   default to "None".  Slice objects have read-only data attributes
   "start", "stop" and "step" which merely return the argument values
   (or their default).  They have no other explicit functionality;
   however they are used by Numerical Python and other third party
   extensions. Slice objects are also generated when extended indexing
   syntax is used.  For example: "a[start:stop:step]" or
   "a[start:stop, i]".  See "itertools.islice()" for an alternate
   version that returns an iterator.

sorted(iterable[, key][, reverse])

   Return a new sorted list from the items in *iterable*.

   Has two optional arguments which must be specified as keyword
   arguments.

   *key* specifies a function of one argument that is used to extract
   a comparison key from each list element: "key=str.lower".  The
   default value is "None" (compare the elements directly).

   *reverse* is a boolean value.  If set to "True", then the list
   elements are sorted as if each comparison were reversed.

   Use "functools.cmp_to_key()" to convert an old-style *cmp* function
   to a *key* function.

   The built-in "sorted()" function is guaranteed to be stable. A sort
   is stable if it guarantees not to change the relative order of
   elements that compare equal — this is helpful for sorting in
   multiple passes (for example, sort by department, then by salary
   grade).

   For sorting examples and a brief sorting tutorial, see Sorting HOW
   TO.

staticmethod(function)

   Return a static method for *function*.

   A static method does not receive an implicit first argument. To
   declare a static method, use this idiom:

      class C:
          @staticmethod
          def f(arg1, arg2, ...): ...

   The "@staticmethod" form is a function *decorator* – see the
   description of function definitions in Function definitions for
   details.

   It can be called either on the class (such as "C.f()") or on an
   instance (such as "C().f()").  The instance is ignored except for
   its class.

   Static methods in Python are similar to those found in Java or C++.
   Also see "classmethod()" for a variant that is useful for creating
   alternate class constructors.

   For more information on static methods, consult the documentation
   on the standard type hierarchy in The standard type hierarchy.

class str(object='')
class str(object=b'', encoding='utf-8', errors='strict')

   Return a "str" version of *object*.  See "str()" for details.

   "str" is the built-in string *class*.  For general information
   about strings, see Text Sequence Type — str.

sum(iterable[, start])

   Sums *start* and the items of an *iterable* from left to right and
   returns the total.  *start* defaults to "0". The *iterable*’s items
   are normally numbers, and the start value is not allowed to be a
   string.

   For some use cases, there are good alternatives to "sum()". The
   preferred, fast way to concatenate a sequence of strings is by
   calling "''.join(sequence)".  To add floating point values with
   extended precision, see "math.fsum()".  To concatenate a series of
   iterables, consider using "itertools.chain()".

super([type[, object-or-type]])

   Return a proxy object that delegates method calls to a parent or
   sibling class of *type*.  This is useful for accessing inherited
   methods that have been overridden in a class. The search order is
   same as that used by "getattr()" except that the *type* itself is
   skipped.

   The "__mro__" attribute of the *type* lists the method resolution
   search order used by both "getattr()" and "super()".  The attribute
   is dynamic and can change whenever the inheritance hierarchy is
   updated.

   If the second argument is omitted, the super object returned is
   unbound.  If the second argument is an object, "isinstance(obj,
   type)" must be true.  If the second argument is a type,
   "issubclass(type2, type)" must be true (this is useful for
   classmethods).

   There are two typical use cases for *super*.  In a class hierarchy
   with single inheritance, *super* can be used to refer to parent
   classes without naming them explicitly, thus making the code more
   maintainable.  This use closely parallels the use of *super* in
   other programming languages.

   The second use case is to support cooperative multiple inheritance
   in a dynamic execution environment.  This use case is unique to
   Python and is not found in statically compiled languages or
   languages that only support single inheritance.  This makes it
   possible to implement “diamond diagrams” where multiple base
   classes implement the same method.  Good design dictates that this
   method have the same calling signature in every case (because the
   order of calls is determined at runtime, because that order adapts
   to changes in the class hierarchy, and because that order can
   include sibling classes that are unknown prior to runtime).

   For both use cases, a typical superclass call looks like this:

      class C(B):
          def method(self, arg):
              super().method(arg)    # This does the same thing as:
                                     # super(C, self).method(arg)

   Note that "super()" is implemented as part of the binding process
   for explicit dotted attribute lookups such as
   "super().__getitem__(name)". It does so by implementing its own
   "__getattribute__()" method for searching classes in a predictable
   order that supports cooperative multiple inheritance. Accordingly,
   "super()" is undefined for implicit lookups using statements or
   operators such as "super()[name]".

   Also note that, aside from the zero argument form, "super()" is not
   limited to use inside methods.  The two argument form specifies the
   arguments exactly and makes the appropriate references.  The zero
   argument form only works inside a class definition, as the compiler
   fills in the necessary details to correctly retrieve the class
   being defined, as well as accessing the current instance for
   ordinary methods.

   For practical suggestions on how to design cooperative classes
   using "super()", see guide to using super().

tuple([iterable])

   Rather than being a function, "tuple" is actually an immutable
   sequence type, as documented in Tuples and Sequence Types — list,
   tuple, range.

class type(object)
class type(name, bases, dict)

   With one argument, return the type of an *object*.  The return
   value is a type object and generally the same object as returned by
   "object.__class__".

   The "isinstance()" built-in function is recommended for testing the
   type of an object, because it takes subclasses into account.

   With three arguments, return a new type object.  This is
   essentially a dynamic form of the "class" statement. The *name*
   string is the class name and becomes the "__name__" attribute; the
   *bases* tuple itemizes the base classes and becomes the "__bases__"
   attribute; and the *dict* dictionary is the namespace containing
   definitions for class body and is copied to a standard dictionary
   to become the "__dict__" attribute.  For example, the following two
   statements create identical "type" objects:

   >>> class X:
   ...     a = 1
   ...
   >>> X = type('X', (object,), dict(a=1))

   See also Type Objects.

vars([object])

   Return the "__dict__" attribute for a module, class, instance, or
   any other object with a "__dict__" attribute.

   Objects such as modules and instances have an updateable "__dict__"
   attribute; however, other objects may have write restrictions on
   their "__dict__" attributes (for example, classes use a
   "types.MappingProxyType" to prevent direct dictionary updates).

   Without an argument, "vars()" acts like "locals()".  Note, the
   locals dictionary is only useful for reads since updates to the
   locals dictionary are ignored.

zip(*iterables)

   Make an iterator that aggregates elements from each of the
   iterables.

   Returns an iterator of tuples, where the *i*-th tuple contains the
   *i*-th element from each of the argument sequences or iterables.
   The iterator stops when the shortest input iterable is exhausted.
   With a single iterable argument, it returns an iterator of
   1-tuples.  With no arguments, it returns an empty iterator.
   Equivalent to:

      def zip(*iterables):
          # zip('ABCD', 'xy') --> Ax By
          sentinel = object()
          iterators = [iter(it) for it in iterables]
          while iterators:
              result = []
              for it in iterators:
                  elem = next(it, sentinel)
                  if elem is sentinel:
                      return
                  result.append(elem)
              yield tuple(result)

   The left-to-right evaluation order of the iterables is guaranteed.
   This makes possible an idiom for clustering a data series into
   n-length groups using "zip(*[iter(s)]*n)".  This repeats the *same*
   iterator "n" times so that each output tuple has the result of "n"
   calls to the iterator. This has the effect of dividing the input
   into n-length chunks.

   "zip()" should only be used with unequal length inputs when you
   don’t care about trailing, unmatched values from the longer
   iterables.  If those values are important, use
   "itertools.zip_longest()" instead.

   "zip()" in conjunction with the "*" operator can be used to unzip a
   list:

      >>> x = [1, 2, 3]
      >>> y = [4, 5, 6]
      >>> zipped = zip(x, y)
      >>> list(zipped)
      [(1, 4), (2, 5), (3, 6)]
      >>> x2, y2 = zip(*zip(x, y))
      >>> x == list(x2) and y == list(y2)
      True

__import__(name, globals=None, locals=None, fromlist=(), level=0)

   Note: This is an advanced function that is not needed in everyday
     Python programming, unlike "importlib.import_module()".

   This function is invoked by the "import" statement.  It can be
   replaced (by importing the "builtins" module and assigning to
   "builtins.__import__") in order to change semantics of the "import"
   statement, but doing so is **strongly** discouraged as it is
   usually simpler to use import hooks (see **PEP 302**) to attain the
   same goals and does not cause issues with code which assumes the
   default import implementation is in use.  Direct use of
   "__import__()" is also discouraged in favor of
   "importlib.import_module()".

   The function imports the module *name*, potentially using the given
   *globals* and *locals* to determine how to interpret the name in a
   package context. The *fromlist* gives the names of objects or
   submodules that should be imported from the module given by *name*.
   The standard implementation does not use its *locals* argument at
   all, and uses its *globals* only to determine the package context
   of the "import" statement.

   *level* specifies whether to use absolute or relative imports. "0"
   (the default) means only perform absolute imports.  Positive values
   for *level* indicate the number of parent directories to search
   relative to the directory of the module calling "__import__()" (see
   **PEP 328** for the details).

   When the *name* variable is of the form "package.module", normally,
   the top-level package (the name up till the first dot) is returned,
   *not* the module named by *name*.  However, when a non-empty
   *fromlist* argument is given, the module named by *name* is
   returned.

   For example, the statement "import spam" results in bytecode
   resembling the following code:

      spam = __import__('spam', globals(), locals(), [], 0)

   The statement "import spam.ham" results in this call:

      spam = __import__('spam.ham', globals(), locals(), [], 0)

   Note how "__import__()" returns the toplevel module here because
   this is the object that is bound to a name by the "import"
   statement.

   On the other hand, the statement "from spam.ham import eggs,
   sausage as saus" results in

      _temp = __import__('spam.ham', globals(), locals(), ['eggs', 'sausage'], 0)
      eggs = _temp.eggs
      saus = _temp.sausage

   Here, the "spam.ham" module is returned from "__import__()".  From
   this object, the names to import are retrieved and assigned to
   their respective names.

   If you simply want to import a module (potentially within a
   package) by name, use "importlib.import_module()".

   Changed in version 3.3: Negative values for *level* are no longer
   supported (which also changes the default value to 0).

-[ Footnotes ]-

[1] Note that the parser only accepts the Unix-style end of line
    convention. If you are reading the code from a file, make sure to
    use newline conversion mode to convert Windows or Mac-style
    newlines.
