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How to Think Like a Computer Scientist The PreTeXt Interactive Edition

Section 10.5 List Membership

in and not in are boolean operators that test membership in a sequence. We used them previously with strings and they also work here.
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Check your understanding
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Checkpoint 10.5.1.

What is printed by the following statements?
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alist = [3, 67, "cat", [56, 57, "dog"], [ ], 3.14, False]
print(3.14 in alist)
  • True
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  • Yes, 3.14 is an item in the list alist.
  • False
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  • There are 7 items in the list, 3.14 is one of them.
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Checkpoint 10.5.2.

What is printed by the following statements?
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alist = [3, 67, "cat", [56, 57, "dog"], [ ], 3.14, False]
print(57 in alist)
  • True
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  • in returns True for top level items only. 57 is in a sublist.
  • False
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  • Yes, 57 is not a top level item in alist. It is in a sublist.
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