def attr_func(*attrs, **kwargs):
"""Creates an "attribute function" for given attribute name(s).
Resulting function will retrieve attributes with given names, in order,
from the object that has been passed to it.
For example, ``attr_func('a', 'b')(foo)`` yields the same as ``foo.a.b``
:param attrs: Attribute names
:param default: Optional keyword argument specifying default value
that will be returned when some attribute is not present
:return: Unary attribute function
"""
ensure_argcount(attrs, min_=1)
ensure_keyword_args(kwargs, optional=('default',))
# preprocess argument list:
# * allow dots in arguments, interpreting them as multiple attributes,
# e.g. ``attr_func('a.b')`` as ``attr_func('a', 'b')``
# * make sure the attribute names are valid Python identifiers
attrs = map(ensure_string, attrs)
attrs = flatten(attr.split('.') if '.' in attr else [attr]
for attr in attrs)
for attr in attrs:
if not is_identifier(attr):
raise ValueError("'%s' is not a valid attribute name", attr)
if 'default' in kwargs:
default = kwargs['default']
if len(attrs) == 1:
getattrs = lambda obj: getattr(obj, attrs[0], default)
else:
def getattrs(obj):
for attr in attrs:
try:
obj = getattr(obj, attr)
except AttributeError:
return default
return obj
else:
if len(attrs) == 1:
getattrs = operator.attrgetter(attrs[0])
else:
def getattrs(obj):
for attr in attrs:
obj = getattr(obj, attr)
return obj
return getattrs
def key_func(*keys, **kwargs):
"""Creates a "key function" based on given keys.
Resulting function will perform lookup using specified keys, in order,
on the object passed to it as an argument.
For example, ``key_func('a', 'b')(foo)`` is equivalent to ``foo['a']['b']``.
:param keys: Lookup keys
:param default: Optional keyword argument specifying default value
that will be returned when some lookup key is not present
:return: Unary key function
"""
ensure_argcount(keys, min_=1)
ensure_keyword_args(kwargs, optional=('default',))
keys = list(map(ensure_string, keys))
if 'default' in kwargs:
default = kwargs['default']
def getitems(obj):
for key in keys:
try:
obj = obj[key]
except KeyError:
return default
return obj
else:
if len(keys) == 1:
getitems = operator.itemgetter(keys[0])
else:
def getitems(obj):
for key in keys:
obj = obj[key]
return obj
return getitems
def test_args__none(self):
with self.assertRaises(TypeError):
__unit__.ensure_argcount(None, min_=1, max_=1)
def test_invalid_limits(self):
with self.assertRaises(ValueError) as r:
__unit__.ensure_argcount(self.FEW_ARGS, min_=2, max_=1)
self.assertIn("greater", str(r.exception))
def test_no_limits(self):
with self.assertRaises(ValueError):
__unit__.ensure_argcount(self.FEW_ARGS)
def test_args__exact(self):
__unit__.ensure_argcount(self.FEW_ARGS, min_=self.FEW, max_=self.FEW)
__unit__.ensure_argcount(self.MANY_ARGS,
min_=self.MANY,
max_=self.MANY)
def test_args__exactly_max(self):
__unit__.ensure_argcount(self.MANY_ARGS,
min_=self.LESS_THAN_MANY,
max_=self.MANY)
def test_args__exactly_min(self):
__unit__.ensure_argcount(self.FEW_ARGS,
min_=self.FEW,
max_=self.MORE_THAN_FEW)
def test_args__exact(self):
__unit__.ensure_argcount(self.FEW_ARGS, min_=self.FEW, max_=self.FEW)
__unit__.ensure_argcount(self.MANY_ARGS, min_=self.MANY, max_=self.MANY)
def test_args__more_than_max(self):
with self.assertRaises(TypeError) as r:
__unit__.ensure_argcount(self.MANY_ARGS, max_=self.LESS_THAN_MANY)
self.assertIn("expected at most", str(r.exception))
def test_args__less_than_min(self):
with self.assertRaises(TypeError) as r:
__unit__.ensure_argcount(self.FEW_ARGS, min_=self.MORE_THAN_FEW)
self.assertIn("expected at least", str(r.exception))
def test_args__empty(self):
__unit__.ensure_argcount([], min_=0, max_=0)
__unit__.ensure_argcount([], min_=0, max_=self.MANY)
with self.assertRaises(TypeError):
__unit__.ensure_argcount([], min_=self.FEW)
def test_args__some_object(self):
with self.assertRaises(TypeError):
__unit__.ensure_argcount(object(), min_=1, max_=1)
def test_args__none(self):
with self.assertRaises(TypeError):
__unit__.ensure_argcount(None, min_=1, max_=1)
def test_invalid_limits(self):
with self.assertRaises(ValueError) as r:
__unit__.ensure_argcount(self.FEW_ARGS, min_=2, max_=1)
self.assertIn("greater", str(r.exception))
def test_no_limits(self):
with self.assertRaises(ValueError):
__unit__.ensure_argcount(self.FEW_ARGS)
def test_args__exactly_min(self):
__unit__.ensure_argcount(self.FEW_ARGS,
min_=self.FEW, max_=self.MORE_THAN_FEW)
def test_args__exactly_max(self):
__unit__.ensure_argcount(self.MANY_ARGS,
min_=self.LESS_THAN_MANY, max_=self.MANY)