import warnings
from inspect import isfunction, signature
[docs]def import_name(fullname):
"""Dynamically imports object by its full name.
>>> from datetime import timedelta
>>> import_name('datetime.timedelta') is timedelta
True
"""
namespace, name = fullname.rsplit(".", 1)
obj = __import__(namespace, None, None, [name], 0)
return getattr(obj, name)
[docs]class looks(object): # noqa: N801
"""Performs duck typing checks for two classes.
Typical use::
assert looks(IFoo, ignore_argspec=['pex']).like(Foo)
"""
def __init__(self, cls):
"""
*cls* - a class to be checked
"""
self.cls = cls
[docs] def like(self, cls, notice=None, ignore_funcs=None, ignore_argspec=None):
"""Check if `self.cls` can be used as duck typing for `cls`.
*cls* - class to be checked for duck typing.
*ignore_funcs* - a list of functions to ignore
*ignore_argspec* - a list of functions to ignore arguments spec.
"""
notice = notice or []
ignore_funcs = ignore_funcs or []
ignore_argspec = ignore_argspec or []
basis = declarations(cls, notice=notice)
contestee = declarations(self.cls, notice=notice)
for name in ignore_funcs:
if name not in basis:
warn("'%s': redundant ignore." % name)
return False
for name, t in basis.items():
if name in ignore_funcs:
continue
if name not in contestee:
warn("'%s': is missing." % name)
return False
else:
t2 = contestee[name]
if isfunction(t) and isfunction(t2):
if name in ignore_argspec:
continue
if signature(t) != signature(t2):
warn(
"'%s': argument names or defaults "
"have no match." % name
)
return False
elif t2.__class__ is not t.__class__:
warn("'%s': is not %s." % (name, t.__class__.__name__))
return False
return True
# region: internal details
def declarations(cls, notice):
return dict(
(name, t)
for name, t in cls.__dict__.items()
if name in notice or not name.startswith("_")
)
def warn(message):
warnings.warn(message, stacklevel=3)