Python Xiaobai's dictionary usage notes

 

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Python  dictionary (Dictionary)

  A dictionary is a mutable container model that can store objects of any type.

Each key  -value key=>value pair, separated by a colon  :

Separate each key-value pair with a comma  ,

The entire dictionary is enclosed in curly braces  {} in the following format:

d = {key1 : value1, key2 : value2 }

　create　

>>>dict = {'a': 1, 'b': 2, 'b': '3'};
>>> dict['b']
'3'
>>> dict
{'a': 1, 'b': '3'}

access

#!/usr/bin/python
 
dict = {'Name': 'Zara', 'Age': 7, 'Class': 'First'};
 
print "dict['Name']: ", dict['Name'];
print "dict['Age']: ", dict['Age'];

output

 

Revise

dict = {'Name': 'Zara', 'Age': 7, 'Class': 'First'};
 
dict['Age'] = 8; # update existing entry
dict['School'] = "DPS School"; # Add new entry
 
 
print "dict['Age']: ", dict['Age'];
print "dict['School']: ", dict['School'];

output

delete

 
dict = {'Name': 'Zara', 'Age': 7, 'Class': 'First'};
 
del dict['Name']; # delete entry whose key is 'Name'
dict.clear(); # clear all dictionary entries
del dict ; # delete dictionary

 

Features of the dictionary:

Two appearances of the same key are not allowed. If the same key is assigned twice during creation, the latter value will be remembered, as in the following example:

dict = {'Name': 'Zara', 'Age': 7, 'Name': 'Manni'};
 
print "dict['Name']: ", dict['Name'];

Only output the latter Manni

Keys must be immutable, so they can be numbers, strings, or tuples, but not lists, as in the following example:

dict = {['Name']: 'Zara', 'Age': 7};
 
print "dict['Name']: ", dict['Name'];

 

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