Summary of dictionary operations in python (six types)

This article brings you a summary of dictionary operations in python (six types). It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

The dictionary is represented by {}, which is a series of "key-value" pairs. You can use the key to access the corresponding value. This value can be a number, a string, or anything. python object. Keys and values ​​are separated by colons

, and key-value pairs are separated by commas. For example: A={'color': 'red', 'points': 10}

1. To access the dictionary value

, just specify the dictionary name and key of the dictionary.

A={'a':7,'b':'happy'}
print(A['a'])
>>>7

2. Add key-value pairs

A={'a':7,'b':'happy'}
A['c']=8
print(A)
>>>{'a': 7, 'b': 'happy', 'c': 8}

3. Modify the value of the key

A={'a':7,'b':'happy'}
A['a']=8
print(A)
>>>{'a': 8, 'b': 'happy'}

4. Delete key-value pairs

A={'a': 7, 'b': 'happy', 'c': 8}
del A['c']
print(A)
>>>A={'a':7,'b':'happy'}

5. Traverse the dictionary

The x and y can be changed according to the actual situation to make it easier to read.

book={
    'number':'0',
    'name':'从入门到放弃',
    'author':'XXX',
    }
for x, y in book.items():   #1、同时取键值对
    print(x+':'+y)
    
for x in book.keys():       #2、只取键
    print(x)
 
for x in book.values():     #3、只取值
    print(x)

When only taking the value, all the values ​​in the dictionary are extracted, and duplicate values ​​are not considered. If you need a list with non-duplicate values, you can use set(), which will automatically remove duplicates. item.

for x in set(book.values()):
    print(x)

6. Nesting

Lists and dictionaries can be nested in dictionaries, depending on the situation.

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