python字典的相关操作

1.增加

dic1 = {'age':18,'name':'xia','sex':'male'}
dic1['high'] = 185
dic1['age'] = 16#如果有，则覆盖值
#如果键不存在于字典中，将会添加键并将值设为默认值。
#如果字典中包含有给定键，则返回该键对应的值，否则返回为该键设置的值。
dic1.setdefault('weight',142)
print (dic1)

{‘age’: 16, ‘name’: ‘xia’, ‘sex’: ‘male’, ‘high’: 185, ‘weight’: 142}

2.删除

dic1 = {'age': 16, 'name': 'xia', 'sex': 'male', 'high': 185, 'weight': 142}
dic1.pop('age')
print (dic1)

{‘name’: ‘xia’, ‘sex’: ‘male’, ‘high’: 185, ‘weight’: 142}

dic1['age'] = 16
print (dic1.pop('age'))#pop删除，返回值对应key的value
print (dic1.pop('erha','none'))#pop删除key，如果key不存在，返回的第二个参数

16
none

dic1.popitem()
print (dic1)
print (dic1.popitem())#返回被删除的key-value

{‘name’: ‘xia’, ‘sex’: ‘male’, ‘high’: 185}
(‘high’, 185)

dic1.clear()#清空字典
del dic1#删除字典

3.改

dic2 = {'name':'zhang','age':18,'sex':'female'}
dic = {'name':'alex','weight':142}
dic2.update(dic)
print (dic)
print (dic2)

{‘name’: ‘alex’, ‘weight’: 142}
{‘name’: ‘alex’, ‘age’: 18, ‘sex’: ‘female’, ‘weight’: 142}

4.查

dic1 = {'age':18,'name':'xia','sex':'male'}
a = dic1.keys()
print (a)
print (dic1.values())
print (dic1.items())

dict_keys([‘age’, ‘name’, ‘sex’])
dict_values([18, ‘xia’, ‘male’])
dict_items([(‘age’, 18), (‘name’, ‘xia’), (‘sex’, ‘male’)])

for i in dic1:
    print (i)

age
name
sex

for k,v in dic1.items():
    print(k,v)

age 18
name xia
sex male

v1 = dic1['name']
print (v1)

xia

v1 = dic1['sss']
print (v1)#不存在会报错

KeyError Traceback (most recent call last)
in ()
----> 1 v1 = dic1[‘ddd’]
2 print(v1)
KeyError: ‘ddd’

print (dic1.get('sss','不存在'))

不存在