Is it possible to forward-declare a function in Python?

Michael Zippo

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Is it possible to forward-declare a function in Python? I want to sort a list using my own cmp function before it is declared.

print "
".join([str(bla) for bla in sorted(mylist, cmp = cmp_configs)])

I"ve organized my code to put the definition of cmp_configs method after the invocation. It fails with this error:

NameError: name "cmp_configs" is not defined

Is there any way to "declare" cmp_configs method before it"s used? It would make my code look cleaner?

I assume that some people will be tempted to tell me that I should just reorganize my code so that I don"t have this problem. However, there are cases when this is probably unavoidable, for instance when implementing some forms of recursion. If you don"t like this example, assume that I have a case in which it"s really necessary to forward declare a function.

Consider this case where forward-declaring a function would be necessary in Python:

def spam():
    if end_condition():
        return end_result()
    else:
        return eggs()

def eggs():
    if end_condition():
        return end_result()
    else:
        return spam()

Where end_condition and end_result have been previously defined.

Is the only solution to reorganize the code and always put definitions before invocations?

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We hope this article has helped you to resolve the problem. Apart from Is it possible to forward-declare a function in Python?, check other code Python module-related topics.

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Frank Krasiko

Warsaw | 2023-03-24

Python-Funktionen und -Methoden is always a bit confusing 😭 Is it possible to forward-declare a function in Python? is not the only problem I encountered. I am just not quite sure it is the best method

Manuel Chamberlet

Prague | 2023-03-24

I was preparing for my coding interview, thanks for clarifying this - Is it possible to forward-declare a function in Python? in Python is not the simplest one. I am just not quite sure it is the best method

Julia Wu

New York | 2023-03-24

Thanks for explaining! I was stuck with Is it possible to forward-declare a function in Python? for some hours, finally got it done 🤗. I just hope that will not emerge anymore