Dictionary
Dictionaries are sometimes found in other languages as “associative memories” or “associative arrays”. Unlike sequences, which are indexed by a range of numbers, dictionaries are indexed by keys, which can be any immutable type.
It is best to think of a dictionary as an unordered set of key: value pairs, with the requirement that the keys are unique (within one dictionary). A pair of braces creates an empty dictionary: {}. Placing a comma-separated list of key:value pairs within the braces adds initial key:value pairs to the dictionary.
Functions
dict.clear(): Remove all items from the dictionary.dict.get(key[, default]): Return the value for key if key is in the dictionary, else default. If default is not given, it defaults to None, so that this method never raises a KeyError.dict.has_key(key): Test for the presence of key in the dictionary.dict.items(): Return a copy of the dictionary’s list of (key, value) pairs.dict.keys(): Return a copy of the dictionary’s list of keys.dict.pop(key[, default]): If key is in the dictionary, remove it and return its value, else return default. If default is not given and key is not in the dictionary, a KeyError is raised.dict.setdefault(key[, default]): If key is in the dictionary, return its value. If not, insert key with a value of default and return default. default defaults to None.dict.update([other]): Update the dictionary with the key/value pairs from other, overwriting existing keys. Return None.dict.values(): Return a copy of the dictionary’s list of values.
Example
a = {"name": "Bo", "age": 20}
print a.has_key("name") # True
print a.keys() # ['name', 'age']
print a.values() # ['Bo', 20]
a.setdefault("gender", "m")
print a # {'name': 'Bo', 'age': 20, 'gender': 'm'}
a.update({"city": "Stony Brook"})
print a # {'name': 'Bo', 'age': 20, 'gender': 'm', 'city': 'Stony Brook'}