Detailed explanation of how to use dict dictionary in python3

This article mainly introduces how to use dict (dictionary) in python3. The article gives a detailed list of functions, which has certain reference value for everyone. Friends who need it can take a look below.

1. clear (clear the dictionary contents)

stu = {
  'num1':'Tom',
  'num2':'Lucy',
  'num3':'Sam',
}
print(stu.clear())

#输出：None

2. copy (copy the dictionary)

stu = {
  'num1':'Tom',
  'num2':'Lucy',
  'num3':'Sam',
}
stu2 = stu.copy()
print(stu2)

3. fromkeys (specify a list, use the values ​​in the list as the keys of the dictionary, and generate a dictionary)

name = ['tom','lucy','sam']
print(dict.fromkeys(name))
print(dict.fromkeys(name,25)) #指定默认值

#输出：{'tom': None, 'lucy': None, 'sam': None}
#   {'tom': 25, 'lucy': 25, 'sam': 25}

4. get (specify key, get the corresponding value)

stu = {
  'num1':'Tom',
  'num2':'Lucy',
  'num3':'Sam',
}
print(stu.get('num2'))

#输出：Lucy

5. items (returns a list of "elements composed of key-value pairs")

stu = {
  'num1':'Tom',
  'num2':'Lucy',
  'num3':'Sam',
}
print(stu.items())

#输出：dict_items([('num2', 'Lucy'), ('num3', 'Sam'), ('num1', 'Tom')])

6. keys( Get all the keys in the dictionary)

##

stu = {
  'num1':'Tom',
  'num2':'Lucy',
  'num3':'Sam',
}
print(stu.keys())

#输出：dict_keys(['num3', 'num1', 'num2'])

7. pop (get the value of the specified key and delete it in the dictionary)

##

stu = {
  'num1':'Tom',
  'num2':'Lucy',
  'num3':'Sam',
}
name = stu.pop('num2')
print(name,stu)

#输出：Lucy {'num1': 'Tom', 'num3': 'Sam'}

8. popitem (randomly obtain a key-value pair and delete it in the dictionary)

stu = {
  'num1':'Tom',
  'num2':'Lucy',
  'num3':'Sam',
}
name = stu.popitem()
print(name,stu)

#输出：('num2', 'Lucy') {'num3': 'Sam', 'num1': 'Tom'}

9. setdefault (get the value of the specified key, if the key does not exist, create it)

stu = {
  'num1':'Tom',
  'num2':'Lucy',
  'num3':'Sam',
}
name = stu.setdefault('num5')
print(name,stu)

#输出：None {'num1': 'Tom', 'num2': 'Lucy', 'num5': None, 'num3': 'Sam'}

10. update (add key-value pair to dictionary)

stu = {
  'num1':'Tom',
  'num2':'Lucy',
  'num3':'Sam',
}
stu.update({'num4':'Ben'})
print(stu)

#输出：{'num2': 'Lucy', 'num3': 'Sam', 'num1': 'Tom', 'num4': 'Ben'}

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