Viewing file:  import_string.py (3.04 KB) -rw-r--r--
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# (c) 2005 Ian Bicking and contributors; written for Paste (http://pythonpaste.org)
# Licensed under the MIT license: http://www.opensource.org/licenses/mit-license.php
"""
'imports' a string -- converts a string to a Python object, importing
any necessary modules and evaluating the expression. Everything
before the : in an import expression is the module path; everything
after is an expression to be evaluated in the namespace of that
module.
Alternately, if no : is present, then import the modules and get the
attributes as necessary. Arbitrary expressions are not allowed in
that case.
"""
def eval_import(s):
"""
Import a module, or import an object from a module.
A module name like ``foo.bar:baz()`` can be used, where
``foo.bar`` is the module, and ``baz()`` is an expression
evaluated in the context of that module. Note this is not safe on
arbitrary strings because of the eval.
"""
if ':' not in s:
return simple_import(s)
module_name, expr = s.split(':', 1)
module = import_module(module_name)
obj = eval(expr, module.__dict__)
return obj
def simple_import(s):
"""
Import a module, or import an object from a module.
A name like ``foo.bar.baz`` can be a module ``foo.bar.baz`` or a
module ``foo.bar`` with an object ``baz`` in it, or a module
``foo`` with an object ``bar`` with an attribute ``baz``.
"""
parts = s.split('.')
module = import_module(parts[0])
name = parts[0]
parts = parts[1:]
last_import_error = None
while parts:
name += '.' + parts[0]
try:
module = import_module(name)
parts = parts[1:]
except ImportError, e:
last_import_error = e
break
obj = module
while parts:
try:
obj = getattr(module, parts[0])
except AttributeError:
raise ImportError(
"Cannot find %s in module %r (stopped importing modules with error %s)" % (parts[0], module, last_import_error))
parts = parts[1:]
return obj
def import_module(s):
"""
Import a module.
"""
mod = __import__(s)
parts = s.split('.')
for part in parts[1:]:
mod = getattr(mod, part)
return mod
def try_import_module(module_name):
"""
Imports a module, but catches import errors. Only catches errors
when that module doesn't exist; if that module itself has an
import error it will still get raised. Returns None if the module
doesn't exist.
"""
try:
return import_module(module_name)
except ImportError, e:
if not getattr(e, 'args', None):
raise
desc = e.args[0]
if not desc.startswith('No module named '):
raise
desc = desc[len('No module named '):]
# If you import foo.bar.baz, the bad import could be any
# of foo.bar.baz, bar.baz, or baz; we'll test them all:
parts = module_name.split('.')
for i in range(len(parts)):
if desc == '.'.join(parts[i:]):
return None
raise
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