9.21. Glossary

collection data type

A data type in which the values are made up of components, or elements, that are themselves values.

default value

The value given to an optional parameter if no argument for it is provided in the function call.

dot notation

Use of the dot operator, ., to access functions inside a module, or to access methods and attributes of an object.

immutable data type

A data type whose values cannot be changed. Modifying functions create a totally new object that does not change the original one.


A variable or value used to select a member of an ordered collection, such as a character from a string, or an element from a list.

optional parameter

A parameter written in a function header with an assignment to a default value which it will receive if no corresponding argument is given for it in the function call.


A part of a string (substring) specified by a range of indices. More generally, a subsequence of any sequence type in Python can be created using the slice operator (sequence[start:stop]).


To iterate through the elements of a collection, performing a similar operation on each.


Any of the characters that move the cursor without printing visible characters. The constant string.whitespace contains all the white-space characters.

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