How do I forward-declare a function to avoid `NameError`s for functions defined later?
16:13 19 Oct 2009

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

I've 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?

Sometimes, it is difficult to reorganize code to avoid this problem. For instance, when implementing some forms of recursion:

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?

python forward-declaration