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break

The break statement causes an immediate exit from a loop. Because the code that follows it in the loop is not executed if the break is reached, you can also sometimes avoid nesting by including a break. For example, here is a simple interactive loop (a variant of a larger example we studied in Chapter 10) that inputs data with input (known as raw_input in Python 2.6) and exits when the user enters “stop” for the name request:

>>> while True:
...     name = input('Enter name:')
...     if name == 'stop': break
...     age  = input('Enter age: ')
...     print('Hello', name, '=>', int(age) ** 2)
...
Enter name:mel
Enter age: 40
Hello mel => 1600
Enter name:bob
Enter age: 30
Hello bob => 900
Enter name:stop

Notice how this code converts the age input to an integer with int before raising it to the second power; as you’ll recall, this is necessary because input returns user input as a string. In Chapter 35, you’ll see that input also raises an exception at end-of-file (e.g., if the user types Ctrl-Z or Ctrl-D); if this matters, wrap input in try statements.