Python Language Reference Manual by Guido van Rossum and Fred L. Drake, Jr. Paperback (6"x9"), 120 pages ISBN 0954161785 RRP £12.95 ($19.95) Sales of this book support the Python Software Foundation! Get a printed copy>>>

Python Language Reference Manual Buy the book here! >>> support free software

5.3.2 Subscriptions

A subscription selects an item of a sequence (string, tuple or list) or mapping (dictionary) object:

subscription primary "[" expression_list "]"

The primary must evaluate to an object of a sequence or mapping type.

If the primary is a mapping, the expression list must evaluate to an object whose value is one of the keys of the mapping, and the subscription selects the value in the mapping that corresponds to that key. (The expression list is a tuple except if it has exactly one item.)

If the primary is a sequence, the expression (list) must evaluate to a plain integer. If this value is negative, the length of the sequence is added to it (so that, e.g., x[-1] selects the last item of x.) The resulting value must be a nonnegative integer less than the number of items in the sequence, and the subscription selects the item whose index is that value (counting from zero).

A string's items are characters. A character is not a separate data type but a string of exactly one character.