# 文件对象

Python’s built-in file objects are implemented entirely on the `FILE*` support from the C standard library. This is an implementation detail and may change in future releases of Python.

`PyFileObject`

  This subtype of `PyObject` represents a Python file object.

PyTypeObject `PyFile_Type`

  This instance of `PyTypeObject` represents the Python file type. This is exposed to Python programs as `file` and `types.FileType`.

int `PyFile_Check`(PyObject *p)

  Return true if its argument is a `PyFileObject` or a subtype of `PyFileObject`.

  在 2.2 版更改: Allowed subtypes to be accepted.

int `PyFile_CheckExact`(PyObject *p)

  Return true if its argument is a `PyFileObject`, but not a subtype of `PyFileObject`.

  2.2 新版功能.

PyObject* `PyFile_FromString`(char *filename, char *mode)
  Return value: New reference.

  On success, return a new file object that is opened on the file given by filename, with a file mode given by mode, where mode has the same semantics as the standard C routine `fopen()`. On failure, return NULL.

PyObject* `PyFile_FromFile`(FILE *fp, char *name, char *mode, int (*close)(FILE*))
  Return value: New reference.

  Create a new `PyFileObject` from the already-open standard C file pointer, fp. The function close will be called when the file should be closed. Return NULL and close the file using close on failure. close is optional and can be set to NULL.

FILE* `PyFile_AsFile`(PyObject *p)

  Return the file object associated with p as a `FILE*`.

  If the caller will ever use the returned `FILE*` object while the GIL is released it must also call the `PyFile_IncUseCount()` and `PyFile_DecUseCount()` functions described below as appropriate.

void `PyFile_IncUseCount`(PyFileObject *p)

  Increments the PyFileObject’s internal use count to indicate that the underlying `FILE*` is being used. This prevents Python from calling f_close() on it from another thread. Callers of this must call `PyFile_DecUseCount()` when they are finished with the `FILE*`. Otherwise the file object will never be closed by Python.

  The GIL must be held while calling this function.

  The suggested use is to call this after `PyFile_AsFile()` and before you release the GIL:

      FILE *fp = PyFile_AsFile(p);
      PyFile_IncUseCount(p);
      /* ... */
      Py_BEGIN_ALLOW_THREADS
      do_something(fp);
      Py_END_ALLOW_THREADS
      /* ... */
      PyFile_DecUseCount(p);

  2.6 新版功能.

void `PyFile_DecUseCount`(PyFileObject *p)

  Decrements the PyFileObject’s internal unlocked_count member to indicate that the caller is done with its own use of the `FILE*`. This may only be called to undo a prior call to `PyFile_IncUseCount()`.

  The GIL must be held while calling this function (see the example above).

  2.6 新版功能.

PyObject* `PyFile_GetLine`(PyObject *p, int n)
  Return value: New reference.

  等价于 `p.readline([n])` ，这个函数从对象 p 中读取一行。 p 可以是文件对象或具有 `readline()` 方法的任何对象。 如果 n 是 `0` ，则无论该行的长度如何，都会读取一行。 如果 n 大于``0``，则从文件中读取不超过 n 个字节；可以返回行的一部分。 在这两种情况下，如果立即到达文件末尾，则返回空字符串。 但是，如果 n 小于 `0` ，则无论长度如何都会读取一行，但是如果立即到达文件末尾，则引发 `EOFError`。

PyObject* `PyFile_Name`(PyObject *p)
  Return value: Borrowed reference.

  Return the name of the file specified by p as a string object.

void `PyFile_SetBufSize`(PyFileObject *p, int n)

  Available on systems with `setvbuf()` only. This should only be called immediately after file object creation.

int `PyFile_SetEncoding`(PyFileObject *p, const char *enc)

  Set the file’s encoding for Unicode output to enc. Return `1` on success and `0` on failure.

  2.3 新版功能.

int `PyFile_SetEncodingAndErrors`(PyFileObject *p, const char *enc, *errors)

  Set the file’s encoding for Unicode output to enc, and its error mode to err. Return `1` on success and `0` on failure.

  2.6 新版功能.

int `PyFile_SoftSpace`(PyObject *p, int newflag)

  This function exists for internal use by the interpreter. Set the `softspace` attribute of p to newflag and return the previous value. p does not have to be a file object for this function to work properly; any object is supported (thought its only interesting if the `softspace` attribute can be set). This function clears any errors, and will return `0` as the previous value if the attribute either does not exist or if there were errors in retrieving it. There is no way to detect errors from this function, but doing so should not be needed.

int `PyFile_WriteObject`(PyObject *obj, PyObject *p, int flags)

  将对象 obj 写入文件对象 p 。 flags 唯一支持的标志是 `Py_PRINT_RAW`；如果给定，则写入对象的 `str()` 而不是 `repr()`。成功时返回 `0`，失败时返回 `-1`。 将设置适当的例外。

int `PyFile_WriteString`(const char *s, PyObject *p)

  将字符串 s 写入文件对象 p。 成功返回 `0` 失败返回 `-1`；将设定相应的异常。