Addition, deletion, modification and lookup of dictionary

dictionary

increase

1. Cover if there is, add if not

dic = { ' name ' : ' old boy ' , ' age ' : 56 , ' hobby ' : ' women ' }
dic['sex'] = 'LaddyBoy'
dic['name'] = 'Alex'  

2. If there is, it will not change, if not, add it

dic = { ' name ' : ' old boy ' , ' age ' : 56, ' hobby ' : ' women ' }
dic.setdefault('sex', 'Laddyboy') 
dic.setdefault('name', 'alex')
print(dic)

 

delete

1. pop Delete according to Key, there is a return value, return the value of the corresponding key to delete.

dic = { ' name ' : ' old boy ' , ' age ' : 56, ' hobby ' : ' women ' }
 print (dic.pop( ' age ' )) 
 print (dic.pop( ' age1 ' , ' without this Key... ' ))    #If there is no error, but adding the value will return the value you wrote 
print (dic)

2. clear clears the dictionary

dic = { ' name ' : ' old boy ' , ' age ' : 56, ' hobby ' : ' women ' }
dic.clear()
print (Dec)

 3. pop.item is deleted randomly, there is a return value, and the return is the ancestor, which is the deleted key pair value

dic = { ' name ' : ' old boy ' , ' age ' : 56, ' hobby ' : ' women ' }
 print (dic.popitem())  
 print (dic)

4. del deletes the entire dictionary

     delete by key

dic = {'name': '老男孩', 'age': 56, 'hobby': 'women'}
del dic['name']
print(dic)

change

1. dic['name'] = 'Alex' If there is, it will be overwritten and added if not

2. update update of two dictionaries

dic = {"name": "jin", "age": 18, "sex": "male"}
dic2 = {"name": "alex", "weight": 75}
dic2.update(dic) #Add   all key-value pairs in dic to dic2, dic remains unchanged 
print (dic)   # {'name': 'jin', 'age': 18, 'sex': 'male' '} 
print (dic2)   # {'name': 'jin', 'weight': 75, 'age': 18, 'sex': 'male'}

 

check

1. If there is, return the value, no error is reported

# 1,dic['name']
dic = {'name': '老男孩', 'age': 56, 'hobby': 'women'}
print(dic['name'])

2. If there is, return the value, if not return None

2,dic.get('name')

dic = { ' name ' : ' old boy ' , ' age ' : 56, ' hobby ' : ' women ' } print (dic.get( ' name ' ))
 print (dic.get( ' name1 ' ))
 print ( dic.get( ' name1 ' , ' sb does not have this key ' ))

3. for loop query

    dic.keys(), dic.values(), dic.items() #Similar to list but not the type of list.

# cycle key

dic = {'name': '老男孩', 'age': 56, 'hobby': 'women'}
for key in dic.keys():     
    print(key)

# loop value

dic = {'name': '老男孩', 'age': 56, 'hobby': 'women'}
for value in dic.values():
    print(value)

   # Loop keys and values ​​are assigned separately

dic = {'name': '老男孩', 'age': 56, 'hobby': 'women'}
for k,v in dic.items(): 
    print(k,v)