Must function defs appear earlier than calls?

[Daniel Yoo]

SeeBelow at seebelow.nut wrote:
: Must function defs appear earlier in a file than use of their name?

: If so, is there some way around this?  It's creating a puzzle for me.


Let's work on a concrete example.  Say we want to write something like
this:

###
print square(42)

def square(x):
    return x * x
###

This doesn't work, because when Python hits the 'print square(42)'
statement, it's not aware yet of what 'square' means.  But there is a
way around this:


###
def main():
    print square(42)

def square(x):
    return x * x

if __name__ == '__main__':
    main()
###


Here, we enclose the main flow of our program in a function called
main().  Python doesn't evaluate a function's body until it is called,
so by the time that we hit:

    if __name__ == '__main__':
        main()

we're ok, since both main() and square() are defined.


So to answer your question:

: Must function defs appear earlier in a file than use of their name?

we can allow the use to be earlier in terms of location in the source
file, by using a function definition to delay the evaluation till all
the symbols are in place.


Hope this helps!