"""Utilities to support packages."""
from collections import namedtuple
from functools import singledispatch as simplegeneric
import importlib
import importlib.util
import importlib.machinery
import os
import os.path
import sys
from types import ModuleType
import warnings
__all__ = [
'get_importer', 'iter_importers', 'get_loader', 'find_loader',
'walk_packages', 'iter_modules', 'get_data',
'read_code', 'extend_path',
'ModuleInfo',
]
ModuleInfo = namedtuple('ModuleInfo', 'module_finder name ispkg')
ModuleInfo.__doc__ = 'A namedtuple with minimal info about a module.'
def read_code(stream):
# This helper is needed in order for the PEP 302 emulation to
# correctly handle compiled files
import marshal
magic = stream.read(4)
if magic != importlib.util.MAGIC_NUMBER:
return None
stream.read(12) # Skip rest of the header
return marshal.load(stream)
def walk_packages(path=None, prefix='', onerror=None):
"""Yields ModuleInfo for all modules recursively
on path, or, if path is None, all accessible modules.
'path' should be either None or a list of paths to look for
modules in.
'prefix' is a string to output on the front of every module name
on output.
Note that this function must import all *packages* (NOT all
modules!) on the given path, in order to access the __path__
attribute to find submodules.
'onerror' is a function which gets called with one argument (the
name of the package which was being imported) if any exception
occurs while trying to import a package. If no onerror function is
supplied, ImportErrors are caught and ignored, while all other
exceptions are propagated, terminating the search.
Examples:
# list all modules python can access
walk_packages()
# list all submodules of ctypes
walk_packages(ctypes.__path__, ctypes.__name__+'.')
"""
def seen(p, m={}):
if p in m:
return True
m[p] = True
for info in iter_modules(path, prefix):
yield info
if info.ispkg:
try:
__import__(info.name)
except ImportError:
if onerror is not None:
onerror(info.name)
except Exception:
if onerror is not None:
onerror(info.name)
else:
raise
else:
path = getattr(sys.modules[info.name], '__path__', None) or []
# don't traverse path items we've seen before
path = [p for p in path if not seen(p)]
yield from walk_packages(path, info.name+'.', onerror)
def iter_modules(path=None, prefix=''):
"""Yields ModuleInfo for all submodules on path,
or, if path is None, all top-level modules on sys.path.
'path' should be either None or a list of paths to look for
modules in.
'prefix' is a string to output on the front of every module name
on output.
"""
if path is None:
importers = iter_importers()
elif isinstance(path, str):
raise ValueError("path must be None or list of paths to look for "
"modules in")
else:
importers = map(get_importer, path)
yielded = {}
for i in importers:
for name, ispkg in iter_importer_modules(i, prefix):
if name not in yielded:
yielded[name] = 1
yield ModuleInfo(i, name, ispkg)
@simplegeneric
def iter_importer_modules(importer, prefix=''):
if not hasattr(importer, 'iter_modules'):
return []
return importer.iter_modules(prefix)
# Implement a file walker for the normal importlib path hook
def _iter_file_finder_modules(importer, prefix=''):
if importer.path is None or not os.path.isdir(importer.path):
return
yielded = {}
import inspect
try:
filenames = os.listdir(importer.path)
except OSError:
# ignore unreadable directories like import does
filenames = []
filenames.sort() # handle packages before same-named modules
for fn in filenames:
modname = inspect.getmodulename(fn)
if modname=='__init__' or modname in yielded:
continue
path = os.path.join(importer.path, fn)
ispkg = False
if not modname and os.path.isdir(path) and '.' not in fn:
modname = fn
try:
dircontents = os.listdir(path)
except OSError:
# ignore unreadable directories like import does
dircontents = []
for fn in dircontents:
subname = inspect.getmodulename(fn)
if subname=='__init__':
ispkg = True
break
else:
continue # not a package
if modname and '.' not in modname:
yielded[modname] = 1
yield prefix + modname, ispkg
iter_importer_modules.register(
importlib.machinery.FileFinder, _iter_file_finder_modules)
try:
import zipimport
from zipimport import zipimporter
def iter_zipimport_modules(importer, prefix=''):
dirlist = sorted(zipimport._zip_directory_cache[importer.archive])
_prefix = importer.prefix
plen = len(_prefix)
yielded = {}
import inspect
for fn in dirlist:
if not fn.startswith(_prefix):
continue
fn = fn[plen:].split(os.sep)
if len(fn)==2 and fn[1].startswith('__init__.py'):
if fn[0] not in yielded:
yielded[fn[0]] = 1
yield prefix + fn[0], True
if len(fn)!=1:
continue
modname = inspect.getmodulename(fn[0])
if modname=='__init__':
continue
if modname and '.' not in modname and modname not in yielded:
yielded[modname] = 1
yield prefix + modname, False
iter_importer_modules.register(zipimporter, iter_zipimport_modules)
except ImportError:
pass
def get_importer(path_item):
"""Retrieve a finder for the given path item
The returned finder is cached in sys.path_importer_cache
if it was newly created by a path hook.
The cache (or part of it) can be cleared manually if a
rescan of sys.path_hooks is necessary.
"""
path_item = os.fsdecode(path_item)
try:
importer = sys.path_importer_cache[path_item]
except KeyError:
for path_hook in sys.path_hooks:
try:
importer = path_hook(path_item)
sys.path_importer_cache.setdefault(path_item, importer)
break
except ImportError:
pass
else:
importer = None
return importer
def iter_importers(fullname=""):
"""Yield finders for the given module name
If fullname contains a '.', the finders will be for the package
containing fullname, otherwise they will be all registered top level
finders (i.e. those on both sys.meta_path and sys.path_hooks).
If the named module is in a package, that package is imported as a side
effect of invoking this function.
If no module name is specified, all top level finders are produced.
"""
if fullname.startswith('.'):
msg = "Relative module name {!r} not supported".format(fullname)
raise ImportError(msg)
if '.' in fullname:
# Get the containing package's __path__
pkg_name = fullname.rpartition(".")[0]
pkg = importlib.import_module(pkg_name)
path = getattr(pkg, '__path__', None)
if path is None:
return
else:
yield from sys.meta_path
path = sys.path
for item in path:
yield get_importer(item)
def get_loader(module_or_name):
"""Get a "loader" object for module_or_name
Returns None if the module cannot be found or imported.
If the named module is not already imported, its containing package
(if any) is imported, in order to establish the package __path__.
"""
warnings._deprecated("pkgutil.get_loader",
f"{warnings._DEPRECATED_MSG}; "
"use importlib.util.find_spec() instead",
remove=(3, 14))
if module_or_name in sys.modules:
module_or_name = sys.modules[module_or_name]
if module_or_name is None:
return None
if isinstance(module_or_name, ModuleType):
module = module_or_name
loader = getattr(module, '__loader__', None)
if loader is not None:
return loader
if getattr(module, '__spec__', None) is None:
return None
fullname = module.__name__
else:
fullname = module_or_name
return find_loader(fullname)
def find_loader(fullname):
"""Find a "loader" object for fullname
This is a backwards compatibility wrapper around
importlib.util.find_spec that converts most failures to ImportError
and only returns the loader rather than the full spec
"""
warnings._deprecated("pkgutil.find_loader",
f"{warnings._DEPRECATED_MSG}; "
"use importlib.util.find_spec() instead",
remove=(3, 14))
if fullname.startswith('.'):
msg = "Relative module name {!r} not supported".format(fullname)
raise ImportError(msg)
try:
spec = importlib.util.find_spec(fullname)
except (ImportError, AttributeError, TypeError, ValueError) as ex:
# This hack fixes an impedance mismatch between pkgutil and
# importlib, where the latter raises other errors for cases where
# pkgutil previously raised ImportError
msg = "Error while finding loader for {!r} ({}: {})"
raise ImportError(msg.format(fullname, type(ex), ex)) from ex
return spec.loader if spec is not None else None
def extend_path(path, name):
"""Extend a package's path.
Intended use is to place the following code in a package's __init__.py:
from pkgutil import extend_path
__path__ = extend_path(__path__, __name__)
For each directory on sys.path that has a subdirectory that
matches the package name, add the subdirectory to the package's
__path__. This is useful if one wants to distribute different
parts of a single logical package as multiple directories.
It also looks for *.pkg files beginning where * matches the name
argument. This feature is similar to *.pth files (see site.py),
except that it doesn't special-case lines starting with 'import'.
A *.pkg file is trusted at face value: apart from checking for
duplicates, all entries found in a *.pkg file are added to the
path, regardless of whether they are exist the filesystem. (This
is a feature.)
If the input path is not a list (as is the case for frozen
packages) it is returned unchanged. The input path is not
modified; an extended copy is returned. Items are only appended
to the copy at the end.
It is assumed that sys.path is a sequence. Items of sys.path that
are not (unicode or 8-bit) strings referring to existing
directories are ignored. Unicode items of sys.path that cause
errors when used as filenames may cause this function to raise an
exception (in line with os.path.isdir() behavior).
"""
if not isinstance(path, list):
# This could happen e.g. when this is called from inside a
# frozen package. Return the path unchanged in that case.
return path
sname_pkg = name + ".pkg"
path = path[:] # Start with a copy of the existing path
parent_package, _, final_name = name.rpartition('.')
if parent_package:
try:
search_path = sys.modules[parent_package].__path__
except (KeyError, AttributeError):
# We can't do anything: find_loader() returns None when
# passed a dotted name.
return path
else:
search_path = sys.path
for dir in search_path:
if not isinstance(dir, str):
continue
finder = get_importer(dir)
if finder is not None:
portions = []
if hasattr(finder, 'find_spec'):
spec = finder.find_spec(final_name)
if spec is not None:
portions = spec.submodule_search_locations or []
# Is this finder PEP 420 compliant?
elif hasattr(finder, 'find_loader'):
_, portions = finder.find_loader(final_name)
for portion in portions:
# XXX This may still add duplicate entries to path on
# case-insensitive filesystems
if portion not in path:
path.append(portion)
# XXX Is this the right thing for subpackages like zope.app?
# It looks for a file named "zope.app.pkg"
pkgfile = os.path.join(dir, sname_pkg)
if os.path.isfile(pkgfile):
try:
f = open(pkgfile)
except OSError as msg:
sys.stderr.write("Can't open %s: %s\n" %
(pkgfile, msg))
else:
with f:
for line in f:
line = line.rstrip('\n')
if not line or line.startswith('#'):
continue
path.append(line) # Don't check for existence!
return path
def get_data(package, resource):
"""Get a resource from a package.
This is a wrapper round the PEP 302 loader get_data API. The package
argument should be the name of a package, in standard module format
(foo.bar). The resource argument should be in the form of a relative
filename, using '/' as the path separator. The parent directory name '..'
is not allowed, and nor is a rooted name (starting with a '/').
The function returns a binary string, which is the contents of the
specified resource.
For packages located in the filesystem, which have already been imported,
this is the rough equivalent of
d = os.path.dirname(sys.modules[package].__file__)
data = open(os.path.join(d, resource), 'rb').read()
If the package cannot be located or loaded, or it uses a PEP 302 loader
which does not support get_data(), then None is returned.
"""
spec = importlib.util.find_spec(package)
if spec is None:
return None
loader = spec.loader
if loader is None or not hasattr(loader, 'get_data'):
return None
# XXX needs test
mod = (sys.modules.get(package) or
importlib._bootstrap._load(spec))
if mod is None or not hasattr(mod, '__file__'):
return None
# Modify the resource name to be compatible with the loader.get_data
# signature - an os.path format "filename" starting with the dirname of
# the package's __file__
parts = resource.split('/')
parts.insert(0, os.path.dirname(mod.__file__))
resource_name = os.path.join(*parts)
return loader.get_data(resource_name)
_NAME_PATTERN = None
def resolve_name(name):
"""
Resolve a name to an object.
It is expected that `name` will be a string in one of the following
formats, where W is shorthand for a valid Python identifier and dot stands
for a literal period in these pseudo-regexes:
W(.W)*
W(.W)*:(W(.W)*)?
The first form is intended for backward compatibility only. It assumes that
some part of the dotted name is a package, and the rest is an object
somewhere within that package, possibly nested inside other objects.
Because the place where the package stops and the object hierarchy starts
can't be inferred by inspection, repeated attempts to import must be done
with this form.
In the second form, the caller makes the division point clear through the
provision of a single colon: the dotted name to the left of the colon is a
package to be imported, and the dotted name to the right is the object
hierarchy within that package. Only one import is needed in this form. If
it ends with the colon, then a module object is returned.
The function will return an object (which might be a module), or raise one
of the following exceptions:
ValueError - if `name` isn't in a recognised format
ImportError - if an import failed when it shouldn't have
AttributeError - if a failure occurred when traversing the object hierarchy
within the imported package to get to the desired object.
"""
global _NAME_PATTERN
if _NAME_PATTERN is None:
# Lazy import to speedup Python startup time
import re
dotted_words = r'(?!\d)(\w+)(\.(?!\d)(\w+))*'
_NAME_PATTERN = re.compile(f'^(?P<pkg>{dotted_words})'
f'(?P<cln>:(?P<obj>{dotted_words})?)?$',
re.UNICODE)
m = _NAME_PATTERN.match(name)
if not m:
raise ValueError(f'invalid format: {name!r}')
gd = m.groupdict()
if gd.get('cln'):
# there is a colon - a one-step import is all that's needed
mod = importlib.import_module(gd['pkg'])
parts = gd.get('obj')
parts = parts.split('.') if parts else []
else:
# no colon - have to iterate to find the package boundary
parts = name.split('.')
modname = parts.pop(0)
# first part *must* be a module/package.
mod = importlib.import_module(modname)
while parts:
p = parts[0]
s = f'{modname}.{p}'
try:
mod = importlib.import_module(s)
parts.pop(0)
modname = s
except ImportError:
break
# if we reach this point, mod is the module, already imported, and
# parts is the list of parts in the object hierarchy to be traversed, or
# an empty list if just the module is wanted.
result = mod
for p in parts:
result = getattr(result, p)
return result
