Python's Strongest King (8)--dictionary (dictionary)

1.Python dictionary (Dictionary)

A dictionary is another mutable container model and can store any type of object.

each key value of the dictionary (key=>value) pair with a colon (:) split, Each pair is separated by a comma (,) , and the entire dictionary is included in curly braces ({}) , The format is as Follows:

D = {key1:value1, key2:value2}

the key must be unique, but the value does not have to Be.

The value can take any data type, but the key must be immutable, such as a string, a number, or a tuple.

1.1 Creating a dictionary

Example 1

D = {" demacia Force "" Galen  " " Darbond Explorer "  nerf "= {" night Hunter "" wei en " }

1.2 Accessing values in the dictionary

Example 2:

#!/usr/bin/env python#-*-coding:utf-8-*-#@Time: 2016/9/12 22:17#@Author: WwyxD = {"the power of Demacia":"Galen","Darbond":"nerf",}name= {"Night Hunter": 2, 2:"oh, Viv ."}Print "the name of the output Demacia force:", d["the power of Demacia"]Print "output Ice Shooter's name", d["Ice Shooter"]#no corresponding value throws an exception

Example 2 run Results

output Demacia name: Galen Traceback (most Recent called last): output ice Shooter's name   " e:/python/hello/untitled3/dictionary.py "  in <module>    print" output ice shooter's name ",  d["  Ice shooter "#  No corresponding value throws exception '\xe5\xaf\x92\xe5\x86\xb0\xe5\xb0\x84\ xe6\x89\x8b'

Note: if the dictionary does not have a corresponding key value, it throws an exception, as the previous example runs the result

1.3 Adding elements to a dictionary

Add new content to a dictionary by adding new key / value pairs, Modifying or deleting existing key / value pairs

Example 3

#!/usr/bin/env python#-*-coding:utf-8-*-#@Time: 2016/9/12 22:17#@Author: WwyxD = {"the power of Demacia":"Galen","Darbond":"nerf",}name= {"Night Hunter": 2, 2:"oh, Viv ."}Print "the name of the output Demacia force:", d["the power of Demacia"]d["Ice Shooter"] ="Ash"  #Add new DataPrint "output Ice Shooter's name", d["Ice Shooter"]#no corresponding value throws an exception

Example 3 runs as follows

Output Demacia name of the force: Galen output ice Shooter's name Ash

1.4 Deleting a dictionary element

Example 4:

#!/usr/bin/env python#-*-coding:utf-8-*-#@Time: 2016/9/12 22:17#@Author: WwyxD = {"the power of Demacia":"Galen","Darbond":"nerf",}name= {"Night Hunter": 2, 2:"oh, Viv ."}Print "the name of the output Demacia force:", d["the power of Demacia"]d["Ice Shooter"] ="Ash"  #Add new DataPrint "output Ice Shooter's name", d["Ice Shooter"]deld["Ice Shooter"]#Delete this valuePrint "deleted after output ice Shooter's name", d["Ice Shooter"]#no corresponding value throws an exception

Example 4 Run Results

  output Demacia The name of the force: Galen Traceback (most Recent called last): output ice shooter's name Ash File   " e:/python/hello/untitled3/dictionary.py  , line, in  <module> after deletion the name of the ice shooter  print   "  Delete the name of the ice shooter after deletion  , d["   ice shooter  ] #   No corresponding value throws exception  keyerror:  \xe5\xaf\x92\xe5 \x86\xb0\xe5\xb0\x84\xe6\x89\x8b   

2. Characteristics of dictionary keys

a Dictionary value can take any Python object without restriction , either as a standard object or as a user-defined one, but not a key.

Two important points to keep in mind:

1) The same key is not allowed to appear two Times. When created, if the same key is assigned a value of two times, the latter value is remembered, as in the following example:

Example 5

#!/usr/bin/env python#-*-coding:utf-8-*-#@Time: 2016/9/12 22:17#@Author: WwyxD = {"the power of Demacia":"Galen","Darbond":"nerf",}name= {"Night Hunter": 2, 2:"oh, Viv ."}Print "the name of the output Demacia force:", d["the power of Demacia"]d["Ice Shooter"] ="Ash"  #Add new DataPrint "output Ice Shooter's name", d["Ice Shooter"]d["Ice Shooter"] ="Catherine"  #Modifying DataPrint "modified to output ice Shooter's name", d["Ice Shooter"]#no corresponding value throws an exception

Example 5 Run Results

Output Demacia name of the power: Galen output ice shooter name Ash modified after output ice Shooter's name Catherine

2) The key must be immutable, so it can be used as a number, a string, or a tuple, so you can't use a list .

Example 6

#!/usr/bin/env python#-*-coding:utf-8-*-#@Time: 2016/9/12 22:17#@Author: WwyxName = {("Night Hunter","oh, Viv ."): 2, 2:"oh, Viv ."}Print "the output tuple is the name of (' night Hunter ', ' Vivian '):", name[("Night Hunter","oh, Viv .")]

Example 6 Run Results

The output tuple is the name of (' night Hunter  ' Vivian '): 2

Dictionary built-in functions & Methods

The Python dictionary contains the following built-in Functions:

Serial Number	Functions and descriptions
1	CMP (dict1, Dict2) Compares two dictionary Elements.
2	Len (dict) Calculates the number of dictionary elements, that is, the total number of keys.
3	STR (dict) The output dictionary is a printable string Representation.
4	Type (variable) Returns the type of the variable entered and returns the dictionary type if the variable is a dictionary.

The Python dictionary contains the following built-in Methods:

Serial Number	Functions and descriptions
1	Radiansdict.clear () Delete all elements in a dictionary
2	Radiansdict.copy () Returns a shallow copy of a dictionary
3	Radiansdict.fromkeys () Create a new dictionary with the keys to the dictionary in sequence seq, val is the initial value corresponding to all keys in the dictionary
4	Radiansdict.get (key, Default=none) Returns the value of the specified key if the value does not return the default value in the dictionary
5	Radiansdict.has_key (key) Returns False if the key returns true in the dictionary Dict
6	Radiansdict.items () Returns an array of traversed (key, Value) tuples as a list
7	Radiansdict.keys () Returns a dictionary of all keys in a list
8	Radiansdict.setdefault (key, Default=none) Similar to get (), but if the key does not exist in the dictionary, the key is added and the value is set to default
9	Radiansdict.update (dict2) Update the Key/value pairs of the dictionary dict2 to the Dict
10	Radiansdict.values () Returns all values in the dictionary as a list

Python's Strongest King (8)--dictionary (dictionary)