Kristian Rother at 19:58, 5 February 2013

2013-02-05T19:58:48Z

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{{Cat|Python Commands}}
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== Structuring code with functions ==
A function is an autonomous sub-program with local variables, input and output. In Python, a function definition must be followed by a code block:

<source lang="python">
def calc_price(fruit,n):
'''Returns the price of fruits.'''
if fruit=='banana':
return 0.75 * n

# call the function
print calc_price('banana',10)
</source>

== Parameters ==
Function parameters may have default values. In that case, they become optional.

'''Do not use lists or dictionaries as default values!'''

<source lang="python">
def calc_price(fruit,n=1):
…

print calc_prices('banana')
print calc_prices('banana',100)
</source>

== Return values ==
A function may return values to the program part that called it. More than one value is returned as a tuple. In any case, the return statement ends the functions execution.

<source lang="python">
return 'banana',0.75
</source>

== Good style for writing functions ==
* Each function should have one purpose only.
* A clear name starting with a verb.
* A documentation string (with triple quotes).
* One return type or one modified input object.
* Necessary parameters.
* Optional parameters.
* Do not use global variables in a function.
* Keep functions small (<100 lines).

Functions - Revision history

Kristian Rother at 19:58, 5 February 2013