9. Iterations and Loop Structures

# 9. Iterations and Loop Structures - 9 ITERATIONS AND LOOP...

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9. ITERATIONS AND LOOP STRUCTURES Rocky K. C. Chang October 18, 2015 (Adapted from John Zelle’s slides)

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Objectives To understand the concepts of definite and indefinite loops as they are realized in the Python for and while statements. To understand the programming patterns interactive loop and sentinel loop and their implementations using a Python while statement. To understand the programming pattern end-of-file loop and ways of implementing such loops in Python.
For Loops: A Quick Review The for statement allows us to iterate through a sequence of values. for <var> in <sequence>: <body> The loop index variable var takes on each successive value in the sequence, and the statements in the body of the loop are executed once for each value.

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Indefinite Loops The for loop is a definite loop, meaning that the number of iterations is determined when the loop starts. We can t use a definite loop unless we know the number of iterations ahead of time. The indefinite or conditional loop keeps iterating until certain conditions are met.
Indefinite Loops while <condition>: <body> condition is a Boolean expression, just like in if statements. The body is a sequence of one or more statements.

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• Fall '16
• Rocky Chiang
• loop, infile

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