ImportManager Manage the import process
Importer Base class for replacing standard import functions
BuiltinImporter Emulate the import mechanism for builtin and frozen modules
from warnings import warnpy3k
warnpy3k("the imputil module has been removed in Python 3.0", stacklevel=2)
# note: avoid importing non-builtin modules
import imp ### not available in Jython?
# for the DirectoryImporter
__all__ = ["ImportManager","Importer","BuiltinImporter"]
_ModuleType = type(sys) ### doesn't work in Jython...
"Manage the import process."
def install(self, namespace=vars(__builtin__)):
"Install this ImportManager into the specified namespace."
if isinstance(namespace, _ModuleType):
namespace = vars(namespace)
# Note: we have no notion of "chaining"
# Record the previous import hook, then install our own.
self.previous_importer = namespace['__import__']
self.namespace = namespace
namespace['__import__'] = self._import_hook
#namespace['reload'] = self._reload_hook
"Restore the previous import mechanism."
self.namespace['__import__'] = self.previous_importer
def add_suffix(self, suffix, importFunc):
assert hasattr(importFunc, '__call__')
self.fs_imp.add_suffix(suffix, importFunc)
######################################################################
clsFilesystemImporter = None
def __init__(self, fs_imp=None):
# we're definitely going to be importing something in the future,
# so let's just load the OS-related facilities.
# This is the Importer that we use for grabbing stuff from the
# filesystem. It defines one more method (import_from_dir) for our use.
cls = self.clsFilesystemImporter or _FilesystemImporter
# Initialize the set of suffixes that we recognize and import.
# The default will import dynamic-load modules first, followed by
# .py files (or a .py file's cached bytecode)
for desc in imp.get_suffixes():
if desc[2] == imp.C_EXTENSION:
DynLoadSuffixImporter(desc).import_file)
self.add_suffix('.py', py_suffix_importer)
def _import_hook(self, fqname, globals=None, locals=None, fromlist=None):
"""Python calls this hook to locate and import a module."""
parts = fqname.split('.')
# determine the context of this import
parent = self._determine_import_context(globals)
# if there is a parent, then its importer should manage this import
module = parent.__importer__._do_import(parent, parts, fromlist)
# has the top module already been imported?
top_module = sys.modules[parts[0]]
# look for the topmost module
top_module = self._import_top_module(parts[0])
# the topmost module wasn't found at all.
raise ImportError, 'No module named ' + fqname
# fast-path simple imports
if not top_module.__dict__.get('__ispkg__'):
# __ispkg__ isn't defined (the module was not imported by us),
# In the former case, there is no way that we could import
# sub-modules that occur in the fromlist (but we can't raise an
# error because it may just be names) because we don't know how
# to deal with packages that were imported by other systems.
# In the latter case (__ispkg__ == 0), there can't be any sub-
# modules present, so we can just return.
# In both cases, since len(parts) == 1, the top_module is also
# the "bottom" which is the defined return when a fromlist
importer = top_module.__dict__.get('__importer__')
return importer._finish_import(top_module, parts[1:], fromlist)
# Grrr, some people "import os.path" or do "from os.path import ..."
if len(parts) == 2 and hasattr(top_module, parts[1]):
return getattr(top_module, parts[1])
# If the importer does not exist, then we have to bail. A missing
# importer means that something else imported the module, and we have
# no knowledge of how to get sub-modules out of the thing.
raise ImportError, 'No module named ' + fqname
def _determine_import_context(self, globals):
"""Returns the context in which a module should be imported.
The context could be a loaded (package) module and the imported module
will be looked for within that package. The context could also be None,
meaning there is no context -- the module should be looked for as a
if not globals or not globals.get('__importer__'):
# globals does not refer to one of our modules or packages. That
# implies there is no relative import context (as far as we are
# concerned), and it should just pick it off the standard path.
# The globals refer to a module or package of ours. It will define
# the context of the new import. Get the module/package fqname.
parent_fqname = globals['__name__']
# if a package is performing the import, then return itself (imports
parent = sys.modules[parent_fqname]
assert globals is parent.__dict__
i = parent_fqname.rfind('.')
# a module outside of a package has no particular import context
# if a module in a package is performing the import, then return the
# package (imports refer to siblings)
parent_fqname = parent_fqname[:i]
parent = sys.modules[parent_fqname]
assert parent.__name__ == parent_fqname
def _import_top_module(self, name):
# scan sys.path looking for a location in the filesystem that contains
# the module, or an Importer object that can import the module.
if isinstance(item, _StringType):
module = self.fs_imp.import_from_dir(item, name)
module = item.import_top(name)
def _reload_hook(self, module):
"Python calls this hook to reload a module."
# reloading of a module may or may not be possible (depending on the
# importer), but at least we can validate that it's ours to reload
importer = module.__dict__.get('__importer__')
# okay. it is using the imputil system, and we must delegate it, but
# we don't know what to do (yet)
### we should blast the module dict and do another get_code(). need to
### flesh this out and add proper docco...
raise SystemError, "reload not yet implemented"
"Base class for replacing standard import functions."
def import_top(self, name):
"Import a top-level module."
return self._import_one(None, name, name)
######################################################################
def _finish_import(self, top, parts, fromlist):
# if "a.b.c" was provided, then load the ".b.c" portion down from
# below the top-level module.
bottom = self._load_tail(top, parts)
# if the form is "import a.b.c", then return "a"
# no fromlist: return the top of the import tree
# the top module was imported by self.
# this means that the bottom module was also imported by self (just
# now, or in the past and we fetched it from sys.modules).
# since we imported/handled the bottom module, this means that we can
# also handle its fromlist (and reliably use __ispkg__).
# if the bottom node is a package, then (potentially) import some
# note: if it is not a package, then "fromlist" refers to names in
# the bottom module rather than modules.
# note: for a mix of names and modules in the fromlist, we will
# import all modules and insert those into the namespace of
# the package module. Python will pick up all fromlist names
# from the bottom (package) module; some will be modules that
# we imported and stored in the namespace, others are expected
self._import_fromlist(bottom, fromlist)
# if the form is "from a.b import c, d" then return "b"
def _import_one(self, parent, modname, fqname):
"Import a single module."
# has the module already been imported?
return sys.modules[fqname]
# load the module's code, or fetch the module itself
result = self.get_code(parent, modname, fqname)
module = self._process_result(result, fqname)
# insert the module into its parent
setattr(parent, modname, module)
def _process_result(self, result, fqname):
ispkg, code, values = result
# did get_code() return an actual module? (rather than a code object)
is_module = isinstance(code, _ModuleType)
# use the returned module, or create a new one to exec code into
module = imp.new_module(fqname)
### record packages a bit differently??
module.__importer__ = self
# insert additional values into the module (before executing the code)
module.__dict__.update(values)
# the module is almost ready... make it visible
sys.modules[fqname] = module
# execute the code within the module's namespace
exec code in module.__dict__
if fqname in sys.modules:
# fetch from sys.modules instead of returning module directly.
# also make module's __name__ agree with fqname, in case
# the "exec code in module.__dict__" played games on us.
module = sys.modules[fqname]
def _load_tail(self, m, parts):
"""Import the rest of the modules, down from the top-level module.
Returns the last module in the dotted list of modules.
fqname = "%s.%s" % (m.__name__, part)
m = self._import_one(m, part, fqname)
raise ImportError, "No module named " + fqname
def _import_fromlist(self, package, fromlist):
'Import any sub-modules in the "from" list.'
# if '*' is present in the fromlist, then look for the '__all__'
# variable to find additional items (modules) to import.
fromlist = list(fromlist) + \
list(package.__dict__.get('__all__', []))
# if the name is already present, then don't try to import it (it
# might not be a module!).
if sub != '*' and not hasattr(package, sub):
subname = "%s.%s" % (package.__name__, sub)
submod = self._import_one(package, sub, subname)
raise ImportError, "cannot import name " + subname
def _do_import(self, parent, parts, fromlist):
"""Attempt to import the module relative to parent.
This method is used when the import context specifies that <self>
imported the parent module.
top_fqname = parent.__name__ + '.' + top_name
top_module = self._import_one(parent, top_name, top_fqname)
# this importer and parent could not find the module (relatively)
return self._finish_import(top_module, parts[1:], fromlist)
######################################################################
def get_code(self, 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
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.
raise RuntimeError, "get_code not implemented"
######################################################################
# Some handy stuff for the Importers
# byte-compiled file suffix character
_suffix_char = __debug__ and 'c' or 'o'
# byte-compiled file suffix
_suffix = '.py' + _suffix_char
def _compile(pathname, timestamp):
"""Compile (and cache) a Python source file.
The file specified by <pathname> is compiled to a code object and
Presuming the appropriate privileges exist, the bytecodes will be
saved back to the filesystem for future imports. The source file's
modification timestamp must be provided as a Long value.
codestring = open(pathname, 'rU').read()
if codestring and codestring[-1] != '\n':
codestring = codestring + '\n'
code = __builtin__.compile(codestring, pathname, 'exec')
# try to cache the compiled code
f = open(pathname + _suffix_char, 'wb')
f.write(struct.pack('<I', timestamp))
_os_stat = _os_path_join = None
"Set up 'os' module replacement functions for use during import bootstrap."
names = sys.builtin_module_names
raise ImportError, 'no os specific module found'
if lastchar == '/' or lastchar == sep:
def _os_path_isdir(pathname):
"Local replacement for os.path.isdir()."
return (s.st_mode & 0170000) == 0040000
def _timestamp(pathname):
"Return the file modification time as a Long."
######################################################################
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