Python Sets

A Set is a list of unique items. Unordered and unindexed, with no duplicate members

A set can be used to remove duplicate entries from a list, or ensure data does not get duplicated. If a record already exists in a set, it doesn't change.

>>> x = set(['foo', 'bar', 'baz', 'foo', 'qux'])

>>> x

{'qux', 'foo', 'bar', 'baz'}

>>> x = set(('foo', 'bar', 'baz', 'foo', 'qux'))

>>> x

{'qux', 'foo', 'bar', 'baz'}

Python Dicts

A list of unique 'keys' pointing to records for fast access. Unordered, changeable and indexed. No duplicate members

The contents of a dict can be written as a series of key : value pairs within braces { }, e.g. dict = {key1:value1, key2:value2, ... }. The "empty dict" is just an empty pair of curly braces {}.

Looking up or setting a value in a dict uses square brackets, e.g. dict['foo'] looks up the value under the key 'foo'. Strings, numbers, and tuples work as keys, and any type can be a value. Other types may or may not work correctly as keys (strings and tuples work cleanly since they are immutable). Looking up a value which is not in the dict throws a KeyError -- use "in" to check if the key is in the dict, or use dict.get(key) which returns the value or None if the key is not present (or get(key, not-found) allows you to specify what value to return in the not-found case).

  dict = {}

  dict['a'] = 'alpha'

  dict['g'] = 'gamma'

  dict['o'] = 'omega'

  print dict  ## {'a': 'alpha', 'o': 'omega', 'g': 'gamma'}