> Since I'm new to python and don't really know how to write programs yet, my
> first question would be what exactly is the main function, because we did a
> similar assignment before this one that included it, and I'm not sure what
> exactly it does.
When you write a program, you write a collection of function and
variable definitions. But they don't have to be in too particular of
an order. For example, we might have something like
#########################
def f(x): return x * x
def g(x): return x**0.5
def h(a, b): return g(f(a) + f(b))
#########################
But nothing stops us from writing the definitions in a different order:
#########################
def h(a, b): return g(f(a) + f(b))
def g(x): return x**0.5
def f(x): return x * x
#########################
However, it does leave the question of: how do you start a program,
and from where do things begin?
In most programming languages, you choose a particular function and
designate it as the "main" entry point into your program.
#########################
def h(a, b): return g(f(a) + f(b))
def g(x): return x**0.5
def f(x): return x * x
def main():
print("The hypotenuse is: %d" % h(3, 4))
#########################
In Python, you don't have to call it "main", but in several other
languages, you do.
There's one more piece you add to the bottom of the program to start
things going, a snippet that looks like this:
if __name__ == '__main__':
main()
This is a purely Python issue. It says that if the file is being run
as the main program (in which case, the __name__ is '__main__'), then
kick things off by calling the main function. You put this at the
bottom of your program.
#########################
def h(a, b): return g(f(a) + f(b))
def g(x): return x**0.5
def f(x): return x * x
def main():
print("The hypotenuse is: %d" % h(3, 4))
if __name__ == '__main__':
main()
#########################
See:
http://effbot.org/pyfaq/tutor-what-is-if-name-main-for.htm
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