31.3. imputil — Import utilities

2.6 版后已移除: The imputil module has been removed in Python 3.

This module provides a very handy and useful mechanism for custom import hooks. Compared to the older ihooks module, imputil takes a dramatically simpler and more straight-forward approach to custom import functions.

class imputil.ImportManager([fs_imp])

Manage the import process.

install([namespace])

Install this ImportManager into the specified namespace.

uninstall()

Restore the previous import mechanism.

add_suffix(suffix, importFunc)

Undocumented.

class imputil.Importer

Base class for replacing standard import functions.

import_top(name)

Import a top-level module.

get_code(parent, modname, fqname)

Find and retrieve the code for the given module.

parent specifies a parent module to define a context for importing. It may be None, indicating no particular context for the search.

modname specifies a single module (not dotted) within the parent.

fqname specifies the fully-qualified module name. This is a (potentially) dotted name from the “root” of the module namespace down to the modname.

If there is no parent, then modname==fqname.

This method should return None, or a 3-tuple.

• If the module was not found, then None should be returned.
• The first item of the 2- or 3-tuple should be the integer 0 or 1, specifying whether the module that was found is a package or not.
• The second item is the code object for the module (it will be executed within the new module’s namespace). This item can also be a fully-loaded module object (e.g. loaded from a shared lib).
• The third item is a dictionary of name/value pairs that will be inserted into new module before the code object is executed. This is provided in case the module’s code expects certain values (such as where the module was found). When the second item is a module object, then these names/values will be inserted after the module has been loaded/initialized.

class imputil.BuiltinImporter

Emulate the import mechanism for built-in and frozen modules. This is a sub-class of the Importer class.

get_code(parent, modname, fqname)

Undocumented.

imputil.py_suffix_importer(filename, finfo, fqname)

Undocumented.

class imputil.DynLoadSuffixImporter([desc])

Undocumented.

import_file(filename, finfo, fqname)

Undocumented.

31.3.1. Examples

This is a re-implementation of hierarchical module import.

This code is intended to be read, not executed. However, it does work – all you need to do to enable it is “import knee”.

(The name is a pun on the clunkier predecessor of this module, “ni”.)

import sys, imp, __builtin__

# Replacement for __import__()
def import_hook(name, globals=None, locals=None, fromlist=None):
    parent = determine_parent(globals)
    q, tail = find_head_package(parent, name)
    m = load_tail(q, tail)
    if not fromlist:
        return q
    if hasattr(m, "__path__"):
        ensure_fromlist(m, fromlist)
    return m

def determine_parent(globals):
    if not globals or  not globals.has_key("__name__"):
        return None
    pname = globals['__name__']
    if globals.has_key("__path__"):
        parent = sys.modules[pname]
        assert globals is parent.__dict__
        return parent
    if '.' in pname:
        i = pname.rfind('.')
        pname = pname[:i]
        parent = sys.modules[pname]
        assert parent.__name__ == pname
        return parent
    return None

def find_head_package(parent, name):
    if '.' in name:
        i = name.find('.')
        head = name[:i]
        tail = name[i+1:]
    else:
        head = name
        tail = ""
    if parent:
        qname = "%s.%s" % (parent.__name__, head)
    else:
        qname = head
    q = import_module(head, qname, parent)
    if q: return q, tail
    if parent:
        qname = head
        parent = None
        q = import_module(head, qname, parent)
        if q: return q, tail
    raise ImportError("No module named " + qname)

def load_tail(q, tail):
    m = q
    while tail:
        i = tail.find('.')
        if i < 0: i = len(tail)
        head, tail = tail[:i], tail[i+1:]
        mname = "%s.%s" % (m.__name__, head)
        m = import_module(head, mname, m)
        if not m:
            raise ImportError("No module named " + mname)
    return m

def ensure_fromlist(m, fromlist, recursive=0):
    for sub in fromlist:
        if sub == "*":
            if not recursive:
                try:
                    all = m.__all__
                except AttributeError:
                    pass
                else:
                    ensure_fromlist(m, all, 1)
            continue
        if sub != "*" and not hasattr(m, sub):
            subname = "%s.%s" % (m.__name__, sub)
            submod = import_module(sub, subname, m)
            if not submod:
                raise ImportError("No module named " + subname)

def import_module(partname, fqname, parent):
    try:
        return sys.modules[fqname]
    except KeyError:
        pass
    try:
        fp, pathname, stuff = imp.find_module(partname,
                                              parent and parent.__path__)
    except ImportError:
        return None
    try:
        m = imp.load_module(fqname, fp, pathname, stuff)
    finally:
        if fp: fp.close()
    if parent:
        setattr(parent, partname, m)
    return m


# Replacement for reload()
def reload_hook(module):
    name = module.__name__
    if '.' not in name:
        return import_module(name, name, None)
    i = name.rfind('.')
    pname = name[:i]
    parent = sys.modules[pname]
    return import_module(name[i+1:], name, parent)


# Save the original hooks
original_import = __builtin__.__import__
original_reload = __builtin__.reload

# Now install our hooks
__builtin__.__import__ = import_hook
__builtin__.reload = reload_hook

Also see the importers module (which can be found in Demo/imputil/ in the Python source distribution) for additional examples.