File Objects

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.

type 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.

Changed in version 2.2: Allowed subtypes to be accepted.

int PyFile_CheckExact(PyObject *p)

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

New in version 2.2.

PyObject *PyFile_FromString(char *filename, char *mode)

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*))

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);

New in version 2.6.

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).

New in version 2.6.

PyObject *PyFile_GetLine(PyObject *p, int n)

Equivalent to p.readline([n]), this function reads one line from the object p. p may be a file object or any object with a readline() method. If n is 0, exactly one line is read, regardless of the length of the line. If n is greater than 0, no more than n bytes will be read from the file; a partial line can be returned. In both cases, an empty string is returned if the end of the file is reached immediately. If n is less than 0, however, one line is read regardless of length, but EOFError is raised if the end of the file is reached immediately.

PyObject *PyFile_Name(PyObject *p)

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.

New in version 2.3.

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.

New in version 2.6.

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)

Write object obj to file object p. The only supported flag for flags is Py_PRINT_RAW; if given, the str() of the object is written instead of the repr(). Return 0 on success or -1 on failure; the appropriate exception will be set.

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

Write string s to file object p. Return 0 on success or -1 on failure; the appropriate exception will be set.