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import typing
def check_type(name: str, value: typing.Any, typeinfo: type) -> None:
"""
This function checks if the provided value is an instance of typeinfo
and raises a TypeError otherwise.
The following types from the typing package have specialized support:
- Union
- Tuple
- IO
"""
# If we realize that we need to extend this list substantially, it may make sense
# to use typeguard for this, but right now it's not worth the hassle for 16 lines of code.
e = TypeError("Expected {} for {}, but got {}.".format(
typeinfo,
name,
type(value)
))
typename = str(typeinfo)
if typename.startswith("typing.Union"):
try:
types = typeinfo.__args__ # type: ignore
except AttributeError:
# Python 3.5.x
types = typeinfo.__union_params__ # type: ignore
for T in types:
try:
check_type(name, value, T)
except TypeError:
pass
else:
return
raise e
elif typename.startswith("typing.Tuple"):
try:
types = typeinfo.__args__ # type: ignore
except AttributeError:
# Python 3.5.x
types = typeinfo.__tuple_params__ # type: ignore
if not isinstance(value, (tuple, list)):
raise e
if len(types) != len(value):
raise e
for i, (x, T) in enumerate(zip(value, types)):
check_type("{}[{}]".format(name, i), x, T)
return
elif typename.startswith("typing.Sequence"):
try:
T = typeinfo.__args__[0] # type: ignore
except AttributeError:
# Python 3.5.0
T = typeinfo.__parameters__[0] # type: ignore
if not isinstance(value, (tuple, list)):
raise e
for v in value:
check_type(name, v, T)
elif typename.startswith("typing.IO"):
if hasattr(value, "read"):
return
else:
raise e
elif not isinstance(value, typeinfo):
raise e
|
