for...in

In Python, you can loop over iterable objects:

>>> a = [0, 1, 'hello', 'python']
>>> for i in a:
...     print i
... 
0
1
hello
python

One common shortcut is xrange, which generates an iterable range without storing the entire list of elements.

>>> for i in xrange(0, 4):
...     print i
... 
0
1
2
3

This is equivalent to the C/C++/C#/Java syntax:

for(int i=0; i<4; i=i+1) { print(i); }

Another useful command is enumerate, which counts while looping:

>>> a = [0, 1, 'hello', 'python']
>>> for i, j in enumerate(a):
...     print i, j
... 
0 0
1 1
2 hello
3 python

There is also a keyword range(a, b, c) that returns a list of integers starting with the value a, incrementing by c, and ending with the last value smaller than b, a defaults to 0 and c defaults to 1. xrange is similar but does not actually generate the list, only an iterator over the list; thus it is better for looping.

You can jump out of a loop using break

>>> for i in [1, 2, 3]:
...     print i
...     break
... 
1

You can jump to the next loop iteration without executing the entire code block with continue

>>> for i in [1, 2, 3]:
...     print i
...     continue
...     print 'test'
... 
1
2
3