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59 lines
1.7 KiB
Python
59 lines
1.7 KiB
Python
#!/usr/bin/env python3
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# Play around with function annotations to implement a crude type checker.
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import inspect
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def typechecked(func):
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wrapped_func = func
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def typecheck(*args, **kvargs):
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parameters = inspect.signature(wrapped_func).parameters
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wants = [(par, parameters[par].annotation) for par in parameters]
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for want, arg in zip(wants, args):
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name, class_ = want
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if not isinstance(arg, class_):
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raise TypeError("arg {} is not "
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"an instance of {}".format(name, class_))
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return_ = wrapped_func(*args, **kvargs)
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class_ = wrapped_func.__annotations__["return"]
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if not isinstance(return_, class_):
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raise TypeError("return value is not "
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"an instance of {}".format(class_))
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return return_
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typecheck.__doc__ = wrapped_func.__doc__
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return typecheck
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@typechecked
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def greet(name: str, age: int, fnord: str=None) -> str:
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"""Greet someone.
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>>> greet("Mike", 12)
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'Hello Mike, you are 12 years old'
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>>> greet("Florian", "eins")
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Traceback (most recent call last):
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File "func_annotations.py", line 14, in typecheck
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"is not an instance of {}".format(name, class_))
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TypeError: arg age is not an instance of <class 'int'>
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"""
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return 'Hello {0}, you are {1} years old'.format(name, age)
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@typechecked
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def test(foo: int) -> str:
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""" Just a test.
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>>> test(1)
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Traceback (most recent call last):
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File "func_annotations.py", line 21, in typecheck
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"is not an instance of {}".format(class_))
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TypeError: return value is not an instance of <class 'str'>
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"""
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return 1
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import doctest
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doctest.testmod()
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