 |
 |
 |
Python Library Reference |  |
 |
 |
|
|
|
Python Library Reference | |
|
|
This module provides an interface to the mechanisms used to implement the import statement. It defines the following constants and functions:
(suffix, mode,
type), where suffix is a string to be appended to the
module name to form the filename to search for, mode is the mode
string to pass to the built-in open() function to open the
file (this can be 'r' for text files or 'rb' for binary
files), and type is the file type, which has one of the values
PY_SOURCE, PY_COMPILED, or
C_EXTENSION, described below.
None, the
list of directory names given by sys.path is searched, but
first it searches a few special places: it tries to find a built-in
module with the given name (C_BUILTIN), then a frozen module
(PY_FROZEN), and on some systems some other places are looked
in as well (on the Mac, it looks for a resource (PY_RESOURCE);
on Windows, it looks in the registry which may point to a specific
file).
If search is successful, the return value is a triple
(file, pathname, description) where
file is an open file object positioned at the beginning,
pathname is the pathname of the
file found, and description is a triple as contained in the list
returned by get_suffixes() describing the kind of module found.
If the module does not live in a file, the returned file is
None, filename is the empty string, and the
description tuple contains empty strings for its suffix and
mode; the module type is as indicate in parentheses above. If the
search is unsuccessful, ImportError is raised. Other
exceptions indicate problems with the arguments or environment.
This function does not handle hierarchical module names (names
containing dots). In order to find P.M, that is, submodule
M of package P, use find_module() and
load_module() to find and load package P, and then use
find_module() with the path argument set to
P.__path__. When P itself has a dotted name, apply
this recipe recursively.
None and '', respectively, when the module is not being
loaded from a file. The description argument is a tuple, as
would be returned by get_suffixes(), describing what kind
of module must be loaded.
If the load is successful, the return value is the module object; otherwise, an exception (usually ImportError) is raised.
Important: the caller is responsible for closing the
file argument, if it was not None, even when an exception
is raised. This is best done using a try
... finally statement.
sys.modules.
On platforms with threads, a thread executing an import holds an internal lock until the import is complete. This lock blocks other threads from doing an import until the original import completes, which in turn prevents other threads from seeing incomplete module objects constructed by the original thread while in the process of completing its import (and the imports, if any, triggered by that).
The following constants with integer values, defined in this module, are used to indicate the search result of find_module().
The following constant and functions are obsolete; their functionality is available through find_module() or load_module(). They are kept around for backward compatibility:
None is returned.
None is returned. (Frozen modules are modules written in
Python whose compiled byte-code object is incorporated into a
custom-built Python interpreter by Python's freeze utility.
See Tools/freeze/ for now.)
1 if there is a built-in module called name which
can be initialized again. Return -1 if there is a built-in
module called name which cannot be initialized again (see
init_builtin()). Return 0 if there is no built-in
module called name.
1 if there is a frozen module (see
init_frozen()) called name, or 0 if there is
no such module.
|
|
|
Python Library Reference | |
|
|