How to change key-value pairs in python dictionary

How to change key-value pairs in python dictionary?

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Modify Dictionary

To Dictionary The way to add new content is to add new key/value pairs, modify or delete existing key/value pairs. The following examples:

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'];

The output results of the above examples:

dict['Age']:  8
dict['School']:  DPS School

1. in the dictionary When the key exists, you can access the value corresponding to the key in the dictionary through the dictionary name subscript. If the key does not exist, an exception will be thrown. If you want to add elements directly to the dictionary, you can add dictionary elements directly using the dictionary name subscript value. If you only write the key and assign the key value later, an exception will be thrown.

>> > a
['apple', 'banana', 'pear', 'orange']
>> > a = {1: 'apple', 2: 'banana', 3: 'pear', 4: 'orange'}
>> > a
{1: 'apple', 2: 'banana', 3: 'pear', 4: 'orange'}
>> > a[2]
'banana'
>> > a[5]
Traceback(most
recent
call
last):
File
"", line
1, in < module >
a[5]
KeyError: 5
>> > a[6] = 'grap'
>> > a
{1: 'apple', 2: 'banana', 3: 'pear', 4: 'orange', 6: 'grap'}

2. Use the update method to add the key-value pairs with corresponding keys in the dictionary to the current dictionary

>>> a
{1: 'apple', 2:'banana', 3: 'pear', 4: 'orange', 6: 'grap'}  
>>>a.items() 
dict_items([(1,'apple'), (2, 'banana'), (3, 'pear'), (4, 'orange'), (6, 'grap')])  
>>>a.update({1:10,2:20})  
>>> a  
{1: 10, 2: 20,3: 'pear', 4: 'orange', 6: 'grap'}  
#{1:10,2:20}替换了{1: 'apple', 2: 'banana'}

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