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The simplest form of a loop in Python is the while loop.

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So, let's make a working copy of while.py, while-working.py, and we'll go ahead

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and open our working copy there.

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The while loop is controlled with the while keyword, which we can see here, and

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then there is an expression.

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So, the expression gets evaluated, and if the expression is true, then the code

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inside the loop, the suite, is executed.

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After that code is executed, the expression is evaluated again, and if it's still

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true, the code gets executed again.

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This continues until the expression is evaluated as false, and then the execution

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begins after the while loop.

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So, let's go ahead and run this, and there is our Fibonacci series.

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So, this expression is b<50, so as long as the result there is <50, the while

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loop will continue.

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So, if I were to increase this to say 150, save that, and run it, then we get a few

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more numbers out there in the Fibonacci series.

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So, while is the simplest form of loop in Python, and you can see all it does is

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it evaluates this expression.

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As long as the expression is true, it executes the code in the while loop, and as

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soon as the expression is not true, the loop ends.

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So, that's the while loop in Python.