How to know function return type and argument types?

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While I am aware of the duck-typing concept of Python, I sometimes struggle with the type of arguments of functions, or the type of the return value of the function.

Now, if I wrote the function myself, I DO know the types. But what if somebody wants to use and call my functions, how is he/she expected to know the types? I usually put type information in the function"s docstring (like: "...the id argument should be an integer..." and "... the function will return a (string, [integer]) tuple.")

But is looking up the information in the docstring (and putting it there, as a coder) really the way it is supposed to be done?

Edit: While the majority of answers seem to direct towards "yes, document!" I feel this is not always very easy for "complex" types.
For example: how to describe concisely in a docstring that a function returns a list of tuples, with each tuple of the form (node_id, node_name, uptime_minutes) and that the elements are respectively a string, string and integer?
The docstring PEP documentation doesn"t give any guidelines on that.
I guess the counterargument will be that in that case classes should be used, but I find python very flexible because it allows passing around these things using lists and tuples, i.e. without classes.

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We hope this article has helped you to resolve the problem. Apart from How to know function return type and argument types?, check other __del__-related topics.

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Walter Wu

Tallinn | 2023-02-06

Maybe there are another answers? What How to know function return type and argument types? exactly means?. I am just not quite sure it is the best method

Chen Wu

New York | 2023-02-06

Thanks for explaining! I was stuck with How to know function return type and argument types? for some hours, finally got it done 🤗. Checked yesterday, it works!

Julia Sikorski

Massachussetts | 2023-02-06

Simply put and clear. Thank you for sharing. How to know function return type and argument types? and other issues with re Python module was always my weak point 😁. I just hope that will not emerge anymore

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