
The Very High Level Layer
*************************

The functions in this chapter will let you execute Python source code
given in a file or a buffer, but they will not let you interact in a
more detailed way with the interpreter.

Several of these functions accept a start symbol from the grammar as a
parameter.  The available start symbols are ``Py_eval_input``,
``Py_file_input``, and ``Py_single_input``.  These are described
following the functions which accept them as parameters.

Note also that several of these functions take ``FILE*`` parameters.
On particular issue which needs to be handled carefully is that the
``FILE`` structure for different C libraries can be different and
incompatible.  Under Windows (at least), it is possible for
dynamically linked extensions to actually use different libraries, so
care should be taken that ``FILE*`` parameters are only passed to
these functions if it is certain that they were created by the same
library that the Python runtime is using.

int Py_Main(int argc, char **argv)

   The main program for the standard interpreter.  This is made
   available for programs which embed Python.  The *argc* and *argv*
   parameters should be prepared exactly as those which are passed to
   a C program's ``main`` function.  It is important to note that the
   argument list may be modified (but the contents of the strings
   pointed to by the argument list are not). The return value will be
   the integer passed to the ``sys.exit()`` function, ``1`` if the
   interpreter exits due to an exception, or ``2`` if the parameter
   list does not represent a valid Python command line.

int PyRun_AnyFile(FILE *fp, const char *filename)

   This is a simplified interface to ``PyRun_AnyFileExFlags`` below,
   leaving *closeit* set to ``0`` and *flags* set to *NULL*.

int PyRun_AnyFileFlags(FILE *fp, const char *filename, PyCompilerFlags *flags)

   This is a simplified interface to ``PyRun_AnyFileExFlags`` below,
   leaving the *closeit* argument set to ``0``.

int PyRun_AnyFileEx(FILE *fp, const char *filename, int closeit)

   This is a simplified interface to ``PyRun_AnyFileExFlags`` below,
   leaving the *flags* argument set to *NULL*.

int PyRun_AnyFileExFlags(FILE *fp, const char *filename, int closeit, PyCompilerFlags *flags)

   If *fp* refers to a file associated with an interactive device
   (console or terminal input or Unix pseudo-terminal), return the
   value of ``PyRun_InteractiveLoop``, otherwise return the result of
   ``PyRun_SimpleFile``.  If *filename* is *NULL*, this function uses
   ``"???"`` as the filename.

int PyRun_SimpleString(const char *command)

   This is a simplified interface to ``PyRun_SimpleStringFlags``
   below, leaving the *PyCompilerFlags** argument set to NULL.

int PyRun_SimpleStringFlags(const char *command, PyCompilerFlags *flags)

   Executes the Python source code from *command* in the ``__main__``
   module according to the *flags* argument. If ``__main__`` does not
   already exist, it is created.  Returns ``0`` on success or ``-1``
   if an exception was raised.  If there was an error, there is no way
   to get the exception information. For the meaning of *flags*, see
   below.

int PyRun_SimpleFile(FILE *fp, const char *filename)

   This is a simplified interface to ``PyRun_SimpleFileExFlags``
   below, leaving *closeit* set to ``0`` and *flags* set to *NULL*.

int PyRun_SimpleFileFlags(FILE *fp, const char *filename, PyCompilerFlags *flags)

   This is a simplified interface to ``PyRun_SimpleFileExFlags``
   below, leaving *closeit* set to ``0``.

int PyRun_SimpleFileEx(FILE *fp, const char *filename, int closeit)

   This is a simplified interface to ``PyRun_SimpleFileExFlags``
   below, leaving *flags* set to *NULL*.

int PyRun_SimpleFileExFlags(FILE *fp, const char *filename, int closeit, PyCompilerFlags *flags)

   Similar to ``PyRun_SimpleStringFlags``, but the Python source code
   is read from *fp* instead of an in-memory string. *filename* should
   be the name of the file.  If *closeit* is true, the file is closed
   before PyRun_SimpleFileExFlags returns.

int PyRun_InteractiveOne(FILE *fp, const char *filename)

   This is a simplified interface to ``PyRun_InteractiveOneFlags``
   below, leaving *flags* set to *NULL*.

int PyRun_InteractiveOneFlags(FILE *fp, const char *filename, PyCompilerFlags *flags)

   Read and execute a single statement from a file associated with an
   interactive device according to the *flags* argument.  If
   *filename* is *NULL*, ``"???"`` is used instead.  The user will be
   prompted using ``sys.ps1`` and ``sys.ps2``. Returns ``0`` when the
   input was executed successfully, ``-1`` if there was an exception,
   or an error code from the ``errcode.h`` include file distributed as
   part of Python if there was a parse error.  (Note that
   ``errcode.h`` is not included by ``Python.h``, so must be included
   specifically if needed.)

int PyRun_InteractiveLoop(FILE *fp, const char *filename)

   This is a simplified interface to ``PyRun_InteractiveLoopFlags``
   below, leaving *flags* set to *NULL*.

int PyRun_InteractiveLoopFlags(FILE *fp, const char *filename, PyCompilerFlags *flags)

   Read and execute statements from a file associated with an
   interactive device until EOF is reached.  If *filename* is *NULL*,
   ``"???"`` is used instead.  The user will be prompted using
   ``sys.ps1`` and ``sys.ps2``.  Returns ``0`` at EOF.

struct _node* PyParser_SimpleParseString(const char *str, int start)

   This is a simplified interface to
   ``PyParser_SimpleParseStringFlagsFilename`` below, leaving
   *filename* set to *NULL* and *flags* set to ``0``.

struct _node* PyParser_SimpleParseStringFlags(const char *str, int start, int flags)

   This is a simplified interface to
   ``PyParser_SimpleParseStringFlagsFilename`` below, leaving
   *filename* set to *NULL*.

struct _node* PyParser_SimpleParseStringFlagsFilename(const char *str, const char *filename, int start, int flags)

   Parse Python source code from *str* using the start token *start*
   according to the *flags* argument.  The result can be used to
   create a code object which can be evaluated efficiently. This is
   useful if a code fragment must be evaluated many times.

struct _node* PyParser_SimpleParseFile(FILE *fp, const char *filename, int start)

   This is a simplified interface to ``PyParser_SimpleParseFileFlags``
   below, leaving *flags* set to ``0``

struct _node* PyParser_SimpleParseFileFlags(FILE *fp, const char *filename, int start, int flags)

   Similar to ``PyParser_SimpleParseStringFlagsFilename``, but the
   Python source code is read from *fp* instead of an in-memory
   string.

PyObject* PyRun_String(const char *str, int start, PyObject *globals, PyObject *locals)
    Return value: New reference.

   This is a simplified interface to ``PyRun_StringFlags`` below,
   leaving *flags* set to *NULL*.

PyObject* PyRun_StringFlags(const char *str, int start, PyObject *globals, PyObject *locals, PyCompilerFlags *flags)
    Return value: New reference.

   Execute Python source code from *str* in the context specified by
   the dictionaries *globals* and *locals* with the compiler flags
   specified by *flags*.  The parameter *start* specifies the start
   token that should be used to parse the source code.

   Returns the result of executing the code as a Python object, or
   *NULL* if an exception was raised.

PyObject* PyRun_File(FILE *fp, const char *filename, int start, PyObject *globals, PyObject *locals)
    Return value: New reference.

   This is a simplified interface to ``PyRun_FileExFlags`` below,
   leaving *closeit* set to ``0`` and *flags* set to *NULL*.

PyObject* PyRun_FileEx(FILE *fp, const char *filename, int start, PyObject *globals, PyObject *locals, int closeit)
    Return value: New reference.

   This is a simplified interface to ``PyRun_FileExFlags`` below,
   leaving *flags* set to *NULL*.

PyObject* PyRun_FileFlags(FILE *fp, const char *filename, int start, PyObject *globals, PyObject *locals, PyCompilerFlags *flags)
    Return value: New reference.

   This is a simplified interface to ``PyRun_FileExFlags`` below,
   leaving *closeit* set to ``0``.

PyObject* PyRun_FileExFlags(FILE *fp, const char *filename, int start, PyObject *globals, PyObject *locals, int closeit, PyCompilerFlags *flags)
    Return value: New reference.

   Similar to ``PyRun_StringFlags``, but the Python source code is
   read from *fp* instead of an in-memory string. *filename* should be
   the name of the file. If *closeit* is true, the file is closed
   before ``PyRun_FileExFlags`` returns.

PyObject* Py_CompileString(const char *str, const char *filename, int start)
    Return value: New reference.

   This is a simplified interface to ``Py_CompileStringFlags`` below,
   leaving *flags* set to *NULL*.

PyObject* Py_CompileStringFlags(const char *str, const char *filename, int start, PyCompilerFlags *flags)
    Return value: New reference.

   Parse and compile the Python source code in *str*, returning the
   resulting code object.  The start token is given by *start*; this
   can be used to constrain the code which can be compiled and should
   be ``Py_eval_input``, ``Py_file_input``, or ``Py_single_input``.
   The filename specified by *filename* is used to construct the code
   object and may appear in tracebacks or ``SyntaxError`` exception
   messages.  This returns *NULL* if the code cannot be parsed or
   compiled.

PyObject* PyEval_EvalCode(PyCodeObject *co, PyObject *globals, PyObject *locals)
    Return value: New reference.

   This is a simplified interface to ``PyEval_EvalCodeEx``, with just
   the code object, and the dictionaries of global and local
   variables. The other arguments are set to *NULL*.

PyObject* PyEval_EvalCodeEx(PyCodeObject *co, PyObject *globals, PyObject *locals, PyObject **args, int argcount, PyObject **kws, int kwcount, PyObject **defs, int defcount, PyObject *closure)

   Evaluate a precompiled code object, given a particular environment
   for its evaluation.  This environment consists of dictionaries of
   global and local variables, arrays of arguments, keywords and
   defaults, and a closure tuple of cells.

PyObject* PyEval_EvalFrame(PyFrameObject *f)

   Evaluate an execution frame.  This is a simplified interface to
   PyEval_EvalFrameEx, for backward compatibility.

PyObject* PyEval_EvalFrameEx(PyFrameObject *f, int throwflag)

   This is the main, unvarnished function of Python interpretation.
   It is literally 2000 lines long.  The code object associated with
   the execution frame *f* is executed, interpreting bytecode and
   executing calls as needed. The additional *throwflag* parameter can
   mostly be ignored - if true, then it causes an exception to
   immediately be thrown; this is used for the ``throw()`` methods of
   generator objects.

int PyEval_MergeCompilerFlags(PyCompilerFlags *cf)

   This function changes the flags of the current evaluation frame,
   and returns true on success, false on failure.

int Py_eval_input

   The start symbol from the Python grammar for isolated expressions;
   for use with ``Py_CompileString``.

int Py_file_input

   The start symbol from the Python grammar for sequences of
   statements as read from a file or other source; for use with
   ``Py_CompileString``.  This is the symbol to use when compiling
   arbitrarily long Python source code.

int Py_single_input

   The start symbol from the Python grammar for a single statement;
   for use with ``Py_CompileString``. This is the symbol used for the
   interactive interpreter loop.

struct PyCompilerFlags

   This is the structure used to hold compiler flags.  In cases where
   code is only being compiled, it is passed as ``int flags``, and in
   cases where code is being executed, it is passed as
   ``PyCompilerFlags *flags``.  In this case, ``from __future__
   import`` can modify *flags*.

   Whenever ``PyCompilerFlags *flags`` is *NULL*, ``cf_flags`` is
   treated as equal to ``0``, and any modification due to ``from
   __future__ import`` is discarded.

      struct PyCompilerFlags {
          int cf_flags;
      }

int CO_FUTURE_DIVISION

   This bit can be set in *flags* to cause division operator ``/`` to
   be interpreted as "true division" according to **PEP 238**.
