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.

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).

3.2 Ignore name attribute.

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 ~io.IOBase.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.

single: EOFError (built-in exception)

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 ~io.IOBase.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.

Read a line from the C stream stream into the buffer buf, like the C standard library function !fgets, but treating all of \n, \r and \r\n as line endings (see universal newlines). Any \r or \r\n read from the stream is stored in buf as a single \n.

At most n - 1 characters are stored in buf; reading stops after a newline has been stored or when the end of the file is reached. The result is always null-terminated. stream should be opened in binary mode, so that the C library does not perform its own newline translation.

Return buf on success. Return NULL if no characters could be read, because stream is at end of file, a read error occurred, or n is less than 2. Like !fgets, this function does not distinguish between end of file and a read error, and it does not set an exception.

fobj exists only for backward compatibility and must be NULL.

Overrides the normal behavior of io.open_code to pass its parameter through the provided handler.

The handler is a function of type:

Equivalent of PyObject *(\*)(PyObject *path, void *userData), where path is guaranteed to be PyUnicodeObject.

The userData pointer is passed into the hook function. Since hook functions may be called from different runtimes, this pointer should not refer directly to Python state.

As this hook is intentionally used during import, avoid importing new modules during its execution unless they are known to be frozen or available in sys.modules.

Once a hook has been set, it cannot be removed or replaced, and later calls to PyFile_SetOpenCodeHook will fail. On failure, the function returns -1 and sets an exception if the interpreter has been initialized.

This function is safe to call before Py_Initialize.

setopencodehook "" c.PyFile_SetOpenCodeHook

3.8

Open path with the mode 'rb'. path must be a Python str object. The behavior of this function may be overridden by PyFile_SetOpenCodeHook to allow for some preprocessing of the text.

This is analogous to io.open_code in Python.

On success, this function returns a strong reference to a Python file object. On failure, this function returns NULL with an exception set.

3.8

Similar to PyFile_OpenCodeObject, but path is a UTF-8 encoded const char*.

3.8

single: Py_PRINT_RAW (C macro)

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.

If obj is NULL, write the string "<NULL>".

Return 0 on success or -1 on failure; the appropriate exception will be set.

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

Soft-deprecated API

These are APIs that were included in Python's C API by mistake. They are documented solely for completeness; use other PyFile* APIs instead.

Use PyFile_FromFd with defaults (fd, NULL, "w", -1, NULL, NULL, NULL, 0) instead.

3.15

Type of file-like objects used internally at Python startup when io is not yet available. Use Python open or PyFile_FromFd to create file objects instead.

3.15

The string literal "b", used to open files in binary mode. Exposed for backwards compatibility only.

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