NumPy : Beginner's Guide - Third Edition

Time for action – repeating instructions with loops

We can use the for loop in the following ways:

1. Loop over an ordered sequence, such as a list, and print each item as follows:

   >>> food = ['ham', 'egg', 'spam']
   >>> for snack in food:
   ...     print(snack)
   ...
   ham
   egg
   spam
   

2. And remember that, as always, indentation matters in Python. We loop over a range of values with the built-in range() or xrange() functions. The latter function is slightly more efficient in certain cases. Loop over the numbers 1-9 with a step of 2 as follows:

   >>> for i in range(1, 9, 2):
   ...     print(i)
   ...
   1
   3
   5
   7
   

3. The start and step parameter of the range() function are optional with default values of 1. We can also prematurely end a loop. Loop over the numbers 0-9 and break out of ...