# bytes 对象

当期望带一个字节串形参但却带一个非字节串形参被调用时，这些函数会引发 `TypeError`。

`PyBytesObject`

  这种 `PyObject` 的子类型表示一个 Python 字节对象。

PyTypeObject `PyBytes_Type`

  `PyTypeObject` 的实例代表一个 Python 字节类型，在 Python 层面它与 `bytes` 是相同的对象。

int `PyBytes_Check`(PyObject *o)

  如果对象 o 是字节对象或字节类型的子类型的实例，则返回 true。

int `PyBytes_CheckExact`(PyObject *o)

  如果对象 o 是字节对象，但不是字节类型子类型的实例，则返回 true。

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:

  格式字符 | 类型 | 注释
  --- | --- | ---
  `%%` | 不适用 | 文字%字符。
  `%c` | 整型 | 一个字节，被表示为一个 C 语言的整型
  `%d` | 整型 | Exactly equivalent to `printf("%d")`.
  `%u` | 无符号整型 | Exactly equivalent to `printf("%u")`.
  `%ld` | 长整型 | Exactly equivalent to `printf("%ld")`.
  `%lu` | 无符号长整型 | Exactly equivalent to `printf("%lu")`.
  `%zd` | Py_ssize_t | Exactly equivalent to `printf("%zd")`.
  `%zu` | size_t | Exactly equivalent to `printf("%zu")`.
  `%i` | 整型 | Exactly equivalent to `printf("%i")`.
  `%x` | 整型 | 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.

  无法识别的格式字符会导致将格式字符串的其余所有内容原样复制到结果对象，并丢弃所有多余的参数。

PyObject* `PyBytes_FromFormatV`(const char *format, va_list vargs)

  与 `PyBytes_FromFormat()` 完全相同，除了它需要两个参数。

PyObject* `PyBytes_FromObject`(PyObject *o)

  返回字节表示实现缓冲区协议的对象*o*。

Py_ssize_t `PyBytes_Size`(PyObject *o)

  返回字节对象*o*中字节的长度。

Py_ssize_t `PyBytes_GET_SIZE`(PyObject *o)

  Macro form of `PyBytes_Size()` but without error checking.

char* `PyBytes_AsString`(PyObject *o)

  Return a pointer to the contents of o. The pointer refers to the internal buffer of o, which consists of `len(o) + 1` bytes. The last byte in the buffer is always null, regardless of whether there are any other null bytes. The data must not be modified in any way, unless the object was just created using `PyBytes_FromStringAndSize(NULL, size)`. It must not be deallocated. If o is not a bytes 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 the null-terminated contents of the object obj through the output variables buffer and length.

  If length is NULL, the bytes object may not contain embedded null bytes; if it does, the function returns `-1` and a `ValueError` is raised.

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

  在 3.5 版更改: Previously, `TypeError` was raised when embedded null bytes were encountered in the bytes object.

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 object 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 bytes 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, `MemoryError` is set, and `-1` is returned.