def expect_types(__funcname=_qualified_name, **named):
"""
Preprocessing decorator that verifies inputs have expected types.
Examples
--------
>>> @expect_types(x=int, y=str)
... def foo(x, y):
... return x, y
...
>>> foo(2, '3')
(2, '3')
>>> foo(2.0, '3') # doctest: +NORMALIZE_WHITESPACE +ELLIPSIS
Traceback (most recent call last):
...
TypeError: ...foo() expected a value of type int for argument 'x',
but got float instead.
Notes
-----
A special argument, __funcname, can be provided as a string to override the
function name shown in error messages. This is most often used on __init__
or __new__ methods to make errors refer to the class name instead of the
function name.
"""
for name, type_ in iteritems(named):
if not isinstance(type_, (type, tuple)):
raise TypeError(
"expect_types() expected a type or tuple of types for "
"argument '{name}', but got {type_} instead.".format(
name=name, type_=type_,
)
)
def _expect_type(type_):
# Slightly different messages for type and tuple of types.
_template = (
"%(funcname)s() expected a value of type {type_or_types} "
"for argument '%(argname)s', but got %(actual)s instead."
)
if isinstance(type_, tuple):
template = _template.format(
type_or_types=' or '.join(map(_qualified_name, type_))
)
else:
template = _template.format(type_or_types=_qualified_name(type_))
return make_check(
exc_type=TypeError,
template=template,
pred=lambda v: not isinstance(v, type_),
actual=compose(_qualified_name, type),
funcname=__funcname,
)
return preprocess(**valmap(_expect_type, named))
评论列表
文章目录
