Kristian Rother at 20:09, 5 February 2013

2013-02-05T20:09:39Z

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{{Cat|Python Commands }}
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== Unconditional loops with ''for'' ==
For loops require a sequence of items that is iterated over. This can be a list, a tuple, a string, a dictionary or any Python object that behaves like one of them (e.g. a file). Examples:

<source lang="python">
for i in range(3):
print i

for char in 'ABCD':
print char

for elem in [1,2,3,4]:
print elem
</source>

== Conditional loops with ''while'' ==
While loops require a conditional expression at the beginning. These work in exactly the same way as in if.. elif statements.

<source lang="python">
i = 0
while i < 5:
print i
i = i + 1
</source>

== When to use ''for'' ==

* When the number of iterations is known at the beginning.
* Printing numbers, concatenating a list of strings.
* Modify all elements of a list.

== When to use ''while'' ==

* When there is a exit condition.
* When it may happen that nothing is done at all.
* When the number of repeats depends on user input.
* Searching for a particular element in a list.

Loops with for and while - Revision history

Kristian Rother at 20:09, 5 February 2013