File Objects — Python documentation
File Objects
These APIs are a minimal emulation of the Python 2 C API for built-in file objects, which used to rely on the buffered I/O (FILE*
) support from the C standard library. In Python 3, files and streams use the new io module, which defines several layers over the low-level unbuffered I/O of the operating system. The functions described below are convenience C wrappers over these new APIs, and meant mostly for internal error reporting in the interpreter; third-party code is advised to access the io APIs instead.
- PyFile_FromFd(int fd, const char *name, const char *mode, int buffering, const char *encoding, const char *errors, const char *newline, int closefd)
Create a Python file object from the file descriptor of an already opened file fd. The arguments name, encoding, errors and newline can be NULL to use the defaults; buffering can be -1 to use the default. name is ignored and kept for backward compatibility. Return NULL on failure. For a more comprehensive description of the arguments, please refer to the io.open() function documentation.
Warning
Since Python streams have their own buffering layer, mixing them with OS-level file descriptors can produce various issues (such as unexpected ordering of data).
Changed in version 3.2: Ignore name attribute.
- int PyObject_AsFileDescriptor(PyObject *p)
- Return the file descriptor associated with p as an
int
. If the object is an integer, its value is returned. If not, the object’s fileno() method is called if it exists; the method must return an integer, which is returned as the file descriptor value. Sets an exception and returns-1
on failure.
- 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 is0
, exactly one line is read, regardless of the length of the line. If n is greater than0
, 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 than0
, however, one line is read regardless of length, but EOFError is raised if the end of the file is reached immediately.
- 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(). Return0
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.