字典增删查

dict1 = {'a':1,'b':2,'c':3}
#增
dict1['d'] = 4
print(dict1)   #{'a': 1, 'b': 2, 'c': 3, 'd': 4}

#删  del
del dict1['a']
print(dict1)  #{'b': 2, 'c': 3, 'd': 4}

#清空字典
# dict1.clear()  
# print(dict1)    #{}

#查
#通过字典的key查找对应的value
print(dict1.get('a','默认值'))  #1
#keys()返回所有键
print(dict1.keys())   #dict_keys(['b', 'c', 'd'])
#values()返回所有值
print(dict1.values())  #dict_values([2, 3, 4])
#items()以列表返回可遍历的（键，值）元组数组
print(dict1.items())  #dict_items([('b', 2), ('c', 3), ('d', 4)])

遍历

获取键对应的值

dict1 = {'a':1,'b':2,'c':3}

keys = dict1.keys()
for key in keys:
    value = dict1.get(key)
    print(f'{key}<=>{value}')

输出：

a<=>1
b<=>2
c<=>3

获取键值对

dict1 = {'a':1,'b':2,'c':3}

items = dict1.items()
for item in items:
    # print(item)   #每个键值对，例('a',1)
    key,value = item[0],item[1]
    print(f'{key}<=>{value}')

for key,value in dict1.items():
    print(f'{key}<=>{value}')

输出：

a<=>1
b<=>2
c<=>3