Python Data structure-Dictionary of sequences

The dictionary is the only built-in mapping type in Python. (Mappings are data structures that refer to values by name).

The values in the dictionary are not in a special order, but are stored in a specific key. Keys can be numbers, strings, and tuples.

First, create a dictionary:

1. Create a dictionary:

Such as:

phonebook={' Zhangsan ': ' 233333 ', ' Lisi ': ' 322233 ', ' Wangwu ': ' 4323334 '}

A dictionary consists of pairs of keys and their corresponding values (also referred to as key/value pairs). In the phonebook example, the name is the key and the phone number is the value. The keys and values are separated by a colon (:), and the items are separated by commas (,). The entire dictionary is enclosed by a pair of curly braces. An empty dictionary (excluding any items) consists of two curly braces, such as {}.

2. The Dict function creates a dictionary:

2.1. The Dict function establishes a dictionary through other mappings (such as other dictionaries) or sequence pairs (keys, values).

Such as:

>>> items=[(' name ', ' Zhangsan '), (' age ', 44)]
>>> d=dict (items)
>>> D
{' Age ': *, ' name ': ' Zhangsan '}
>>>

2.2, Dict function can also be used to create a dictionary by keyword parameters;

Such as:

>>> a=dict (name= ' Lisi ', age=44)
>>> D
{' Age ': *, ' name ': ' Zhangsan '}
>>>

Note: The Dict function is not a real function, he is a type, just like list, tuple, and Str.

Second, the basic operation of the dictionary:

The basic behavior of the dictionary is similar to the sequence (sequence):

A), Len (d): Returns the number of items in D (key-value pairs);

b), D[k]: Returns the value associated to the key k;

c), D[k]=v: The value V is associated to the key k;

d), Del D[k]: Delete the key to K;

e), k in D check if there is a value in D containing the key k;

Dictionaries and Lists

Python Data structure-Dictionary of sequences