[Tutor] Using a list as function argument?

[Daniel Yoo]

On Wed, 20 Dec 2000, Nate Bargmann wrote:

> I'm wanting to write a function that utilizes several arguments.  As I
> intend to read the arguments out of a file, they are already in a list
> variable.  I would like to pass this list to a function, do my
> processing and then return a list to the calling routine which I can
> use.  I'm just getting starting in Python and I really didn't find an
> answer in the Python tutorial, the FAQ at python.org or in the TYP book.

Let's try to write a function that, given a list of numbers, returns back
a list of those numbers doubled.  Here's a small interpreter session:

###
>>> def doubleNumbers(numbers):
...     results = []  # we'll collect our results in here 
...     for x in numbers:
...         results.append(x + x)
...     return results
... 
>>> doubleNumbers([1, 2, 3, 4, 5])
[2, 4, 6, 8, 10]
>>> doubleNumbers("testing")
['tt', 'ee', 'ss', 'tt', 'ii', 'nn', 'gg']
###

So our doubleNumbers function can work on lists of numbers.  The
surprising thing is that it works on any kind of "sequence" --- anything
that we can do a for-loop around.  Just wanted to play around with it...
*grin*

So basically, you can make an empty list, and collect your results into it
by using its append() function.  This is the skeleton that I use when I
want to process lists.  Hope this helps!