Please provide a better explanation of tuples and dictionaries

John Gordon gordon at panix.com
Wed Jan 30 06:15:43 CET 2013


In <hKCdnWgrOqkwFpXMnZ2dnUVZ_qadnZ2d at o1.com> "Daniel W. Rouse Jr." <dwrousejr at nethere.comNOSPAM> writes:

> I have recently started learning Python (2.7.3) but need a better 
> explanation of how to use tuples and dictionaries.

A tuple is a linear sequence of items, accessed via subscripts that start
at zero.

Tuples are read-only; items cannot be added, removed, nor replaced.

Items in a tuple need not be the same type.

Example:

    >>> my_tuple = (1, 5, 'hello', 9.9999)
    >>> print my_tuple[0]
    1
    >>> print my_tuple[2]
    hello

A dictionary is a mapping type; it allows you to access items via a
meaningful name (usually a string.)

Dictionaries do not preserve the order in which items are created (but
there is a class in newer python versions, collections.OrderedDict, which
does preserve order.)

Example:

    >>> person = {} # start with an empty dictionary
    >>> person['name'] = 'John'
    >>> person['age'] = 40
    >>> person['occupation'] = 'Programmer'
    >>> print person['age']
    40

Dictionaries can also be created with some initial values, like so:

    >>> person = { 'name': 'John', 'age': 40, 'occupation' : 'Programmer' }

-- 
John Gordon                   A is for Amy, who fell down the stairs
gordon at panix.com              B is for Basil, assaulted by bears
                                -- Edward Gorey, "The Gashlycrumb Tinies"




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