Python Sanity Proposal: Type Hinting Solution

Marko Rauhamaa marko at
Sat Jan 24 00:52:45 CET 2015

Mario Figueiredo <marfig at>:
> Much better is:
>       def myfunction(arg1, arg2):
>       """
>       Normal docstring...
>       @typehint: (str, int) -> bool
>       """ 
>           return True 

I seem to remember an idea floated on the Scheme mailing list of using
assertions for such a purpose:

   def myfunction(arg1, arg2):
       assert isinstance(arg1, str) and isinstance(arg2, int)
       return True

The advantage is that the assertions can be as complex as you'd like:

   def weekday(day):
       assert isinstance(day, int) and 0 <= day <= 6

   def str_product(x, y):
       assert isinstance(x, int) and isinstance(y, str) or \
           isinstance(x, str) and isinstance(y, int)

Also, they have always been present in the language and assertion
semantics is fully compatible with static analysis.

Only I'd hate if that style became standard boilerplate...


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