How to Think Like a Computer Scientist The PreTeXt Interactive Edition

Glossary Glossary

indexing ([]).

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Access a single character in a string using its position (starting from 0). Example: 'This'[2] evaluates to 'i'.

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length function (len).

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Returns the number of characters in a string. Example: len('happy') evaluates to 5.

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for loop traversal (for).

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Traversing a string means accessing each character in the string, one at a time. For example, the following for loop:

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for ix in 'Example':
    ...

executes the body of the loop 7 times with different values of ix each time.

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slicing ([:]).

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A slice is a substring of a string. Example: 'bananas and cream'[3:6] evaluates to ana (so does 'bananas and cream'[1:4]).

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string comparison (>, <, >=, <=, ==, !=).

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The six common comparision operators work with strings, evaluating according to lexigraphical order. Examples: 'apple' < 'banana' evaluates to True. 'Zeta' < 'Appricot' evaluates to False. 'Zebra' <= 'aardvark' evaluates to True because all upper case letters precede lower case letters.

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in and not in operator (in, not in).

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The in operator tests whether one string is contained inside another string. Examples: 'heck' in "I'll be checking for you." evaluates to True. 'cheese' in "I'll be checking for you." evaluates to False.

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