cpython/Lib/imputil.py

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#
# imputil.py: import utilities
#
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### docco needed here and in Docs/ ...
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# note: avoid importing non-builtin modules
import imp ### not available in JPython?
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import sys
import strop
import __builtin__
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# for the DirectoryImporter
import struct
import marshal
_StringType = type('')
_ModuleType = type(sys) ### doesn't work in JPython...
class ImportManager:
"Manage the import process."
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def install(self, namespace=vars(__builtin__)):
"Install this ImportManager into the specified namespace."
if isinstance(namespace, _ModuleType):
namespace = vars(namespace)
### Note that we have no notion of "uninstall" or "chaining"
namespace['__import__'] = self._import_hook
### fix this
#namespace['reload'] = self._reload_hook
def add_suffix(self, suffix, importFunc):
assert callable(importFunc)
self.fs_imp.add_suffix(suffix, importFunc)
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######################################################################
#
# PRIVATE METHODS
#
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.
if not _os_stat:
_os_bootstrap()
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# This is the Importer that we use for grabbing stuff from the
# filesystem. It defines one more method (import_from_dir) for our use.
if not fs_imp:
cls = self.clsFilesystemImporter or _FilesystemImporter
fs_imp = cls()
self.fs_imp = fs_imp
# 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:
self.add_suffix(desc[0], DynLoadSuffixImporter(desc).import_file)
self.add_suffix('.py', py_suffix_importer)
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def _import_hook(self, fqname, globals=None, locals=None, fromlist=None):
"""Python calls this hook to locate and import a module."""
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parts = strop.split(fqname, '.')
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# determine the context of this import
parent = self._determine_import_context(globals)
# if there is a parent, then its importer should manage this import
if parent:
module = parent.__importer__._do_import(parent, parts, fromlist)
if module:
return module
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# has the top module already been imported?
try:
top_module = sys.modules[parts[0]]
except KeyError:
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# look for the topmost module
top_module = self._import_top_module(parts[0])
if not top_module:
# the topmost module wasn't found at all.
raise ImportError, 'No module named ' + fqname
# fast-path simple imports
if len(parts) == 1:
if not fromlist:
return top_module
if not top_module.__dict__.get('__ispkg__'):
# __ispkg__ isn't defined (the module was not imported by us), or
# it is zero.
#
# 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 exists.
return top_module
importer = top_module.__dict__.get('__importer__')
if importer:
return importer._finish_import(top_module, parts[1:], fromlist)
# 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
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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
"top-level" module.
"""
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.
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return None
# 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
# refer to pkg contents)
if globals['__ispkg__']:
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parent = sys.modules[parent_fqname]
assert globals is parent.__dict__
return parent
i = strop.rfind(parent_fqname, '.')
# a module outside of a package has no particular import context
if i == -1:
return None
# if a module in a package is performing the import, then return the
# package (imports refer to siblings)
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parent_fqname = parent_fqname[:i]
parent = sys.modules[parent_fqname]
assert parent.__name__ == parent_fqname
return parent
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.
for item in sys.path:
if isinstance(item, _StringType):
module = self.fs_imp.import_from_dir(item, name)
else:
module = item.import_top(name)
if module:
return module
return None
def _reload_hook(self, module):
"Python calls this hook to reload a module."
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# 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__')
if not importer:
### oops. now what...
pass
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# 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"
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class Importer:
"Base class for replacing standard import functions."
def import_top(self, name):
"Import a top-level module."
return self._import_one(None, name, name)
######################################################################
#
# PRIVATE METHODS
#
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"
if not fromlist:
# no fromlist: return the top of the import tree
return top
# 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 modules.
#
# 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
# to be present already.
if bottom.__ispkg__:
self._import_fromlist(bottom, fromlist)
# if the form is "from a.b import c, d" then return "b"
return bottom
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def _import_one(self, parent, modname, fqname):
"Import a single module."
# has the module already been imported?
try:
return sys.modules[fqname]
except KeyError:
pass
# load the module's code, or fetch the module itself
result = self.get_code(parent, modname, fqname)
if result is None:
return None
module = self._process_result(result, fqname)
# insert the module into its parent
if parent:
setattr(parent, modname, module)
return module
def _process_result(self, (ispkg, code, values), fqname):
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# did get_code() return an actual module? (rather than a code object)
is_module = isinstance(code, _ModuleType)
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# use the returned module, or create a new one to exec code into
if is_module:
module = code
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else:
module = imp.new_module(fqname)
### record packages a bit differently??
module.__importer__ = self
module.__ispkg__ = ispkg
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# insert additional values into the module (before executing the code)
module.__dict__.update(values)
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# the module is almost ready... make it visible
sys.modules[fqname] = module
# execute the code within the module's namespace
if not is_module:
exec code in module.__dict__
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return module
def _load_tail(self, m, parts):
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"""Import the rest of the modules, down from the top-level module.
Returns the last module in the dotted list of modules.
"""
for part in parts:
fqname = "%s.%s" % (m.__name__, part)
m = self._import_one(m, part, fqname)
if not m:
raise ImportError, "No module named " + fqname
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return m
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.
if '*' in fromlist:
fromlist = list(fromlist) + list(package.__dict__.get('__all__', []))
for sub in fromlist:
# 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)
if not submod:
raise ImportError, "cannot import name " + subname
def _do_import(self, parent, parts, fromlist):
"""Attempt to import the module relative to parent.
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This method is used when the import context specifies that <self>
imported the parent module.
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"""
top_name = parts[0]
top_fqname = parent.__name__ + '.' + top_name
top_module = self._import_one(parent, top_name, top_fqname)
if not top_module:
# this importer and parent could not find the module (relatively)
return None
return self._finish_import(top_module, parts[1:], fromlist)
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######################################################################
#
# METHODS TO OVERRIDE
#
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 down to the modname.
If there is no parent, then modname==fqname.
This method should return None, or a 3-tuple.
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* 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
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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
returned.
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, 'r').read()
if codestring and codestring[-1] != '\n':
codestring = codestring + '\n'
code = __builtin__.compile(codestring, pathname, 'exec')
# try to cache the compiled code
try:
f = open(pathname + _suffix_char, 'wb')
except IOError:
pass
else:
f.write('\0\0\0\0')
f.write(struct.pack('<I', timestamp))
marshal.dump(code, f)
f.flush()
f.seek(0, 0)
f.write(imp.get_magic())
f.close()
return code
_os_stat = _os_path_join = None
def _os_bootstrap():
"Set up 'os' module replacement functions for use during import bootstrap."
names = sys.builtin_module_names
join = None
if 'posix' in names:
sep = '/'
from posix import stat
elif 'nt' in names:
sep = '\\'
from nt import stat
elif 'dos' in names:
sep = '\\'
from dos import stat
elif 'os2' in names:
sep = '\\'
from os2 import stat
elif 'mac' in names:
from mac import stat
def join(a, b):
if a == '':
return b
path = s
if ':' not in a:
a = ':' + a
if a[-1:] <> ':':
a = a + ':'
return a + b
else:
raise ImportError, 'no os specific module found'
if join is None:
def join(a, b, sep=sep):
if a == '':
return b
lastchar = a[-1:]
if lastchar == '/' or lastchar == sep:
return a + b
return a + sep + b
global _os_stat
_os_stat = stat
global _os_path_join
_os_path_join = join
def _os_path_isdir(pathname):
"Local replacement for os.path.isdir()."
try:
s = _os_stat(pathname)
except OSError:
return None
return (s[0] & 0170000) == 0040000
def _timestamp(pathname):
"Return the file modification time as a Long."
try:
s = _os_stat(pathname)
except OSError:
return None
return long(s[8])
######################################################################
#
# Emulate the import mechanism for builtin and frozen modules
#
class BuiltinImporter(Importer):
def get_code(self, parent, modname, fqname):
if parent:
# these modules definitely do not occur within a package context
return None
# look for the module
if imp.is_builtin(modname):
type = imp.C_BUILTIN
elif imp.is_frozen(modname):
type = imp.PY_FROZEN
else:
# not found
return None
# got it. now load and return it.
module = imp.load_module(modname, None, modname, ('', '', type))
return 0, module, { }
######################################################################
#
# Internal importer used for importing from the filesystem
#
class _FilesystemImporter(Importer):
def __init__(self):
self.suffixes = [ ]
def add_suffix(self, suffix, importFunc):
assert callable(importFunc)
self.suffixes.append((suffix, importFunc))
def import_from_dir(self, dir, fqname):
result = self._import_pathname(_os_path_join(dir, fqname), fqname)
if result:
return self._process_result(result, fqname)
return None
def get_code(self, parent, modname, fqname):
# This importer is never used with an empty parent. Its existence is
# private to the ImportManager. The ImportManager uses the
# import_from_dir() method to import top-level modules/packages.
# This method is only used when we look for a module within a package.
assert parent
return self._import_pathname(_os_path_join(parent.__pkgdir__, modname),
fqname)
def _import_pathname(self, pathname, fqname):
if _os_path_isdir(pathname):
result = self._import_pathname(_os_path_join(pathname, '__init__'),
fqname)
if result:
values = result[2]
values['__pkgdir__'] = pathname
values['__path__'] = [ pathname ]
return 1, result[1], values
return None
for suffix, importFunc in self.suffixes:
filename = pathname + suffix
try:
finfo = _os_stat(filename)
except OSError:
pass
else:
return importFunc(filename, finfo, fqname)
return None
######################################################################
#
# SUFFIX-BASED IMPORTERS
#
def py_suffix_importer(filename, finfo, fqname):
file = filename[:-3] + _suffix
t_py = long(finfo[8])
t_pyc = _timestamp(file)
code = None
if t_pyc is not None and t_pyc >= t_py:
f = open(file, 'rb')
if f.read(4) == imp.get_magic():
t = struct.unpack('<I', f.read(4))[0]
if t == t_py:
code = marshal.load(f)
f.close()
if code is None:
file = filename
code = _compile(file, t_py)
return 0, code, { '__file__' : file }
class DynLoadSuffixImporter:
def __init__(self, desc):
self.desc = desc
def import_file(self, filename, finfo, fqname):
fp = open(filename, self.desc[1])
module = imp.load_module(fqname, fp, filename, self.desc)
module.__file__ = filename
return 0, module, { }
######################################################################
def _print_importers():
items = sys.modules.items()
items.sort()
for name, module in items:
if module:
print name, module.__dict__.get('__importer__', '-- no importer')
else:
print name, '-- non-existent module'
def _test_revamp():
ImportManager().install()
sys.path.insert(0, BuiltinImporter())
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######################################################################
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#
# TODO
#
# from Finn Bock:
# remove use of "strop" -- not available in JPython
# type(sys) is not a module in JPython. what to use instead?
# imp.C_EXTENSION is not in JPython. same for get_suffixes and new_module
#
# given foo.py of:
# import sys
# sys.modules['foo'] = sys
#
# ---- standard import mechanism
# >>> import foo
# >>> foo
# <module 'sys' (built-in)>
#
# ---- revamped import mechanism
# >>> import imputil
# >>> imputil._test_revamp()
# >>> import foo
# >>> foo
# <module 'foo' from 'foo.py'>
#
#
# from MAL:
# should BuiltinImporter exist in sys.path or hard-wired in ImportManager?
# need __path__ processing
# performance
# move chaining to a subclass [gjs: it's been nuked]
# avoid strop
# deinstall should be possible
# query mechanism needed: is a specific Importer installed?
# py/pyc/pyo piping hooks to filter/process these files
# wish list:
# distutils importer hooked to list of standard Internet repositories
# module->file location mapper to speed FS-based imports
# relative imports
# keep chaining so that it can play nice with other import hooks
#
# from Gordon:
# push MAL's mapper into sys.path[0] as a cache (hard-coded for apps)
#
# from Guido:
# need to change sys.* references for rexec environs
# need hook for MAL's walk-me-up import strategy, or Tim's absolute strategy
# watch out for sys.modules[...] == None
# flag to force absolute imports? (speeds _determine_import_context and
# checking for a relative module)
# insert names of archives into sys.path (see quote below)
# note: reload does NOT blast module dict
# shift import mechanisms and policies around; provide for hooks, overrides
# (see quote below)
# add get_source stuff
# get_topcode and get_subcode
# CRLF handling in _compile
# race condition in _compile
# refactoring of os.py to deal with _os_bootstrap problem
# any special handling to do for importing a module with a SyntaxError?
# (e.g. clean up the traceback)
# implement "domain" for path-type functionality using pkg namespace
# (rather than FS-names like __path__)
# don't use the word "private"... maybe "internal"
#
#
# Guido's comments on sys.path caching:
#
# We could cache this in a dictionary: the ImportManager can have a
# cache dict mapping pathnames to importer objects, and a separate
# method for coming up with an importer given a pathname that's not yet
# in the cache. The method should do a stat and/or look at the
# extension to decide which importer class to use; you can register new
# importer classes by registering a suffix or a Boolean function, plus a
# class. If you register a new importer class, the cache is zapped.
# The cache is independent from sys.path (but maintained per
# ImportManager instance) so that rearrangements of sys.path do the
# right thing. If a path is dropped from sys.path the corresponding
# cache entry is simply no longer used.
#
# My/Guido's comments on factoring ImportManager and Importer:
#
# > However, we still have a tension occurring here:
# >
# > 1) implementing policy in ImportManager assists in single-point policy
# > changes for app/rexec situations
# > 2) implementing policy in Importer assists in package-private policy
# > changes for normal, operating conditions
# >
# > I'll see if I can sort out a way to do this. Maybe the Importer class will
# > implement the methods (which can be overridden to change policy) by
# > delegating to ImportManager.
#
# Maybe also think about what kind of policies an Importer would be
# likely to want to change. I have a feeling that a lot of the code
# there is actually not so much policy but a *necessity* to get things
# working given the calling conventions for the __import__ hook: whether
# to return the head or tail of a dotted name, or when to do the "finish
# fromlist" stuff.
#