Revision 5 as of 2017-03-31 23:19:56

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While loops

Usage in Python

While loops, like the ForLoop, are used for repeating sections of code - but unlike a for loop, the while loop will not run n times, but until a defined condition is met. As the for loop in Python is so powerful, while is rarely used, except in cases where a user's input is required, for example:

n = raw_input("Please enter 'hello':")
while n.strip() != 'hello':
    n = raw_input("Please enter 'hello':")

However, the problem with the above code is that it's wasteful. In fact, what you will see a lot of in Python is the following:

while True:
    n = raw_input("Please enter 'hello':")
    if n.strip() == 'hello':
        break

As you can see, this compacts the whole thing into a piece of code managed entirely by the while loop. Having True as a condition ensures that the code runs until it's broken by n.strip() equaling 'hello'.

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