Python3学习笔记：字典

心已赠人 2022-05-22 06:41 212阅读 0赞

Python中的字典用于存储 key-value（键值对）类型数据。

# 字典的表现形式 #

if __name__ == '__main__':
        dict1={1:"a",2:23,4:1+5j}
        dict2={"1":"j","2":2}
        dict3={}
        dict4={"1+2j":4,"4-5j":5}
        dict5={"1+7j":4,"2":5,1:"sdfsdf"}
        dict6={1:dict1,2:dict2,3:dict3,4:dict4,5:dict5}
        print("dict1=",dict1)
        print("dict2=",dict2)
        print("dict3=",dict3)
        print("dict4=",dict4)
        print("dict5=",dict5)
        print("dict6=",dict6)

相应输出为

dict1= {1: 'a', 2: 23, 4: (1+5j)}
    dict2= {'1': 'j', '2': 2}
    dict3= {}
    dict4= {'1+2j': 4, '4-5j': 5}
    dict5= {'1+7j': 4, '2': 5, 1: 'sdfsdf'}
    dict6= {1: {1: 'a', 2: 23, 4: (1+5j)}, 2: {'1': 'j', '2': 2}, 3: {}, 4: {'1+2j': 4, '4-5j': 5}, 5: {'1+7j': 4, '2': 5, 1: 'sdfsdf'}}

（1）字典可以为空，可以嵌套

（2）key可以为任意数据类型，但必须唯一

# 字典元素的访问 #

print("dict1[1] = ", dict1[1])
        print("dict2['1'] =", dict2["1"])
        print("dict4.get['1+2j'] = ",dict4.get("1+2j"))

相应输出为

dict1(1) =  a
    dict2['1'] = j
    dict4.get['1+2j'] =  4

共有两种访问方式

（1）dictname【key】

（2）dictname.get(key)

# 字典元素的修改 #

print("dict1[1] = ",dict1[1])
        dict1[1]=0
        print("dict1[1] = ",dict1[1])
        print("dict5['1+7j']= ",dict5["1+7j"])
        dict5["1+7j"]=2
        print("dict5['1+7j']= ",dict5["1+7j"])

相应输出为

dict1[1] =  a
    dict1[1] =  0
    dict5['1+7j']=  4
    dict5['1+7j']=  2

需要指出的是，get方法不能用于修改。即不能使用dict1.get(1)=0

# 字典元素的删除 #

print("dict1=",dict1)
        del dict1[1]
        print("dict1=",dict1)
        del dict1
    #     print("dict1=",dict1)
        
        print("dict6=",dict6)
        dict6.pop(1)
        print("dict6=",dict6)
        dict6.clear()
        print("dict6=",dict6)

相应输出为

#  #

dict1= {1: 0, 2: 23, 4: (1+5j)}
    dict1= {2: 23, 4: (1+5j)}
    dict6= {1: {2: 23, 4: (1+5j)}, 2: {'1': 'j', '2': 2}, 3: {}, 4: {'1+2j': 4, '4-5j': 5}, 5: {'1+7j': 2, '2': 5, 1: 'sdfsdf'}}
    dict6= {2: {'1': 'j', '2': 2}, 3: {}, 4: {'1+2j': 4, '4-5j': 5}, 5: {'1+7j': 2, '2': 5, 1: 'sdfsdf'}}
    dict6= {}

共有四种删除方式

（1）del dictname\[key\]

（2）dictname.pop\[key\]

（3）del dictname

（4）dictname.clean()

需要指定的是，del字典后，该字典变量就不存在了，因此，不能再次访问。

字典其它工具方法

print("dict5 length = ", len(dict5)) #字典长度
        print("dict5 keys =",dict5.keys()) #字典key集合
        print("dict5 values = ",dict5.values()) #字典值集合
        print("dict5 items =", dict5.items()) #字典item集合

相应输出为

dict5 length =  3
    dict5 keys = dict_keys(['1+7j', '2', 1])
    dict5 values =  dict_values([2, 5, 'sdfsdf'])
    dict5 items = dict_items([('1+7j', 2), ('2', 5), (1, 'sdfsdf')])