Checkpoint 8.7.1.
What is printed by the following statements?
alist = [3, 67, "cat", [56, 57, "dog"], [ ], 3.14, False]
print(3.14 in alist)
- True
- Yes, 3.14 is an item in the list alist.
- False
- There are 7 items in the list, 3.14 is one of them.
Section 8.7 Sequence Conditional Operators
Along with basic comparsion operators, Python also provides built-in operators to create boolean expressions with sequences, such as strings and lists.
The
in operator tests if one string is a substring of another:
Note that a string is a substring of itself, and the empty string is a substring of any other string. (Also note that computer scientists like to think about these edge cases quite carefully!)
Subsection 8.7.1 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.
Check your understanding
Checkpoint 8.7.2.
What is printed by the following statements?
alist = [3, 67, "cat", [56, 57, "dog"], [ ], 3.14, False]
print(57 in alist)
- True
- in returns True for top level items only. 57 is in a sublist.
- False
- Yes, 57 is not a top level item in alist. It is in a sublist.
Checkpoint 8.7.3.
Create one conditional to find whether “false” is in string
str1. If so, assign variable output the string “False. You aren’t you?”. Check to see if “true” is in string str1 and if it is then assign “True! You are you!” to the variable output. If neither are in str1, assign “Neither true nor false!” to output.
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