[Tutor] Need to write a python and call it within a python main program (fwd)

[Danny Yoo]

> I need help on the SYNTAX of Python
>
> I have programming experience in Fortran and a little bit of C.


Ah, ok; let's see if we can transfer some concepts from your previous
experience into Python.

Just as a note: please use your email client's "Reply to All" feature so
that our correspondence stays on the Python-tutor mailing list.  The idea
is that if I say something that is inaccurate or incomplete, the other
helpers can come and compensate for my weaknesses.



> I don't know how to get started.
>
> I've downloaded Python, and have used the idle as a desk calculator, but
> do not yet know how to write programs in it.

You may want to do a quick run-through of:

    http://www.python.org/doc/tut/

which will help give you a better sense of the syntax of the language.




> Do you already know about conditionals?
>
> *******************
>
> I know about the == relational operator.
>
> ***************


Python has a familiar control-flow syntax for branches in the 'if'
statement.  For example, here is an interactive session that shows how one
can use it for a simple case-analysis:

######
>>> def is_even(n):
...     if n % 2 == 0:        ## % is the modulo operator
...         return "yes"
...     else:
...         return "no"
...
>>> is_even(42)
'yes'
>>> is_even(13)
'no'
######

This is a function that takes an argument 'n', and returns either a 'yes'
or 'no' output.  If you look through a tutorial like the official Python
tutorial, you should see more usage of the "if" statement to handle an
arbitrary number of cases.




> Do you know how to test a function?
>
> Do you mean
> (1)  call the function with test values to see if it performs the way you
> want it to?
> (2)  something else that is Python related that I know nothing about?


#1.  I was running under the assumption that you hadn't programmed before.
But since you have, I think you know how to test a program so that you
have a reasonable idea of how well a program is doing what you want.




> Please help me with the syntax.  I don't know how to tell python to run
> a main program and use subroutines.  I don't know how to make those
> subroutines available to the main program.


I think the best thing I can do is point you to tutorials that you can use
to get a handle for the syntax.  There is:

    http://www.python.org/doc/tut/

as I pointed to earlier, but there's also:

    http://wiki.python.org/moin/BeginnersGuide/Programmers

which are tutorials that are targetted toward people who already know how
to program.


If you have more questions, please feel free to email 'tutor at python.org'.
Good luck!