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Lists

A list [1, 2, 3] is an ordered, mutable collection of values. You can add to it with append, get its length with len, and slice it just like strings. A tuple (1, 2) is similar but cannot be changed after it is created.

\text{len}(x)

number of elements in the list

x.\text{append}(v)

adds

v

to the end

Symbols

$x$	a list
$v$	the value being added

Example

x = [1, 2, 3]

x.append(4) makes x [1, 2, 3, 4], and len(x) becomes 4.

Lists are passed to functions by reference: if the function changes the list, you see the change outside too.

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