python 基础知识4

1、字典增

#字典增
dic = {'name': '大白', 'age': 20}
dic['hight'] = 180  #没有键值对，添加
dic['age'] = 18   #有键值对，覆盖
print(dic)
#{'name': '大白', 'age': 20, 'hight': 180}
#{'name': '大白', 'age': 18

#setdefault
dic = {'name': '大白', 'age': 20}
dic.setdefault('weight',150)# 没有height此键，则添加
print(dic)#{'name': '大白', 'age': 20, 'weight': 150}
dic.setdefault('name',150)# 有此键则不变
print(dic)#{'name': '大白', 'age': 20}

2、字典删

dic = {'name': '大白', 'age': 20}
print(dic.pop('age'))#20(有返回值)
print(dic.pop('hight','没有此键'))#没有此键
print(dic)#{'name': '大白'}


#popitem 3.5版本之前，popitem为随机删除，3.6之后为删除最后一个，有返回值
dic = {'name': '大白', 'age': 20}
dic.popitem()
print(dic)#{'name': '大白'}


#clear 清空字典
dic = {'name': '大白', 'age': 20}
dic.clear()
print(dic) # {}

# del
# 通过键删除键值对
dic = {'name': '大白', 'age': 20}
del dic['name']
print(dic) # {'age': 20}
#删除整个字典
del dic

 3、字典改

#update
dic1 = {'name':'jin','age':18,'sex':'mal'}
dic2 = {'name':'alex','weight':75}
dic1.update(dic2)#将2更新到1里
print(dic1) # {'name': 'alex', 'age': 18, 'sex': 'male', 'weight': 75}
print(dic2) # {'name': 'alex', 'weight': 75}

 4、字典查

#keys()查键
dic = {'name': '大白', 'age': 20}
print(dic.keys()) # dict_keys(['name', 'age'])

#values()查键值
dic = {'name': '大白', 'age': 20}
print(dic.values()) #dict_values(['大白', 20])

#items()查键值对
dic = {'name': '大白', 'age': 20}
print(dic.items()) #dict_items([('name', '大白'), ('age', 20)])

for i in dic.items():
    print(i)
# ('name', '大白')
# ('age', 20)

for i,j in dic.items():
    print(i,j)
# name 大白
# age 20

#get
dic = {'name': '大白', 'age': 20}
print(dic.get('age'))#20
print(dic.get('hight'))#（若无）None

 4、dict嵌套

dic = {'name':['大白','python','小白'],
        'py9': {'num': 71, 'age': 18},
        True: 1,
        (1, 2, 3): '123',
        2: '白鸽', }
dic['name'][1]=dic['name'][1].upper()#将'name'中‘python'大写
dic['py9']['female'] = 6#将'female':6添加到'py9'中
print(dic)