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# Bytes Objects

These functions raise `TypeError` when expecting a bytes parameter and are called with a non-bytes parameter.

`PyBytesObject`
  This subtype of `PyObject` represents a Python bytes object.

PyTypeObject `PyBytes_Type`

  This instance of `PyTypeObject` represents the Python bytes type; it is the same object as `bytes` in the Python layer. .

int `PyBytes_Check`(PyObject *o)
  Return true if the object o is a bytes object or an instance of a subtype of the bytes type.

int `PyBytes_CheckExact`(PyObject *o)
  Return true if the object o is a bytes object, but not an instance of a subtype of the bytes type.

PyObject* `PyBytes_FromString`(const char *v)
  Return a new bytes object with a copy of the string v as value on success, and NULL on failure. The parameter v must not be NULL; it will not be checked.

PyObject* `PyBytes_FromStringAndSize`(const char *v, Py_ssize_t len)
  Return a new bytes object with a copy of the string v as value and length len on success, and NULL on failure. If v is NULL, the contents of the bytes object are uninitialized.

PyObject* `PyBytes_FromFormat`(const char *format, ...)

  Take a C `printf`-style format string and a variable number of arguments, calculate the size of the resulting Python bytes object and return a bytes object with the values formatted into it. The variable arguments must be C types and must correspond exactly to the format characters in the format string. The following format characters are allowed:

  Format Characters | Type | Comment
  --- | --- | ---
  `%%` | n/a | The literal % character.
  `%c` | int | A single character, represented as an C int.
  `%d` | int | Exactly equivalent to `printf("%d")`.
  `%u` | unsigned int | Exactly equivalent to `printf("%u")`.
  `%ld` | long | Exactly equivalent to `printf("%ld")`.
  `%lu` | unsigned long | Exactly equivalent to `printf("%lu")`.
  `%zd` | Py_ssize_t | Exactly equivalent to `printf("%zd")`.
  `%zu` | size_t | Exactly equivalent to `printf("%zu")`.
  `%i` | int | Exactly equivalent to `printf("%i")`.
  `%x` | int | Exactly equivalent to `printf("%x")`.
  `%s` | char* | A null-terminated C character array.
  `%p` | void* | The hex representation of a C pointer. Mostly equivalent to `printf("%p")` except that it is guaranteed to start with the literal `0x` regardless of what the platform’s `printf` yields.

  An unrecognized format character causes all the rest of the format string to be copied as-is to the result string, and any extra arguments discarded.

PyObject* `PyBytes_FromFormatV`(const char *format, va_list vargs)
  Identical to `PyBytes_FromFormat()` except that it takes exactly two arguments.

PyObject* `PyBytes_FromObject`(PyObject *o)
  Return the bytes representation of object o that implements the buffer protocol.

Py_ssize_t `PyBytes_Size`(PyObject *o)
  Return the length of the bytes in bytes object o.

Py_ssize_t `PyBytes_GET_SIZE`(PyObject *o)
  Macro form of `PyBytes_Size` but without error checking.

char* `PyBytes_AsString`(PyObject *o)
  Return a NUL-terminated representation of the contents of o. The pointer refers to the internal buffer of o, not a copy. The data must not be modified in any way, unless the string was just created using `PyBytes_FromStringAndSize(NULL, size)`. It must not be deallocated. If o is not a string object at all, `PyBytes_AsString` returns NULL and raises `TypeError`.

char* `PyBytes_AS_STRING`(PyObject *string)
  Macro form of `PyBytes_AsString` but without error checking.

int `PyBytes_AsStringAndSize`(PyObject *obj, char **buffer, Py_ssize_t *length)

  Return a NUL-terminated representation of the contents of the object obj through the output variables buffer and length.

  If length is NULL, the resulting buffer may not contain NUL characters; if it does, the function returns `-1` and a `TypeError` is raised.

  The buffer refers to an internal string buffer of obj, not a copy. The data must not be modified in any way, unless the string was just created using `PyBytes_FromStringAndSize(NULL, size)`. It must not be deallocated. If string is not a string object at all, `PyBytes_AsStringAndSize` returns `-1` and raises `TypeError`.

void `PyBytes_Concat`(PyObject **bytes, PyObject *newpart)
  Create a new bytes object in *bytes containing the contents of newpart appended to bytes; the caller will own the new reference. The reference to the old value of bytes will be stolen. If the new string cannot be created, the old reference to bytes will still be discarded and the value of *bytes will be set to NULL; the appropriate exception will be set.

void `PyBytes_ConcatAndDel`(PyObject **bytes, PyObject *newpart)
  Create a new string object in *bytes containing the contents of newpart appended to bytes. This version decrements the reference count of newpart.

int `_PyBytes_Resize`(PyObject **bytes, Py_ssize_t newsize)
  A way to resize a bytes object even though it is “immutable”. Only use this to build up a brand new bytes object; don’t use this if the bytes may already be known in other parts of the code. It is an error to call this function if the refcount on the input bytes object is not one. Pass the address of an existing bytes object as an lvalue (it may be written into), and the new size desired. On success, *bytes holds the resized bytes object and `0` is returned; the address in *bytes may differ from its input value. If the reallocation fails, the original bytes object at *bytes is deallocated, *bytes is set to NULL, a memory exception is set, and `-1` is returned.

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