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)