python中的字典河流题？

Posted 2023-05-03

rivers='黄河':'河北','长江':'湖南','涅瓦河':'圣彼得堡'
for i in rivers.keys():
print(i+'流经'+rivers[i])
---------------------------------------
rivers[i]为什么要这么写？i里面的不都是key么？

参考技术A 字典是键对值！i是键 字典[i]是值

python基础训练题2-元组,字典

1，判断值在元组中

>>> a = ( 1, 2, 3, 4, 10 )
>>> 10 in a
True
>>> ‘10‘ in a 
False

2，修改元组中的值，由于元组不能被直接修改，可以先把他转成列表，在通过列表修改之后，赋给一个新的元组对象

>>> a = ( 10, 20, 30, 40 )
>>> l = list( a )
>>> l[0] = 100
>>> t = tuple( l )
>>> t
(100, 20, 30, 40)
>>> id( a )
139920488716168
>>> id( t )
139920488447152
>>> type( a )
<type ‘tuple‘>
>>> type( t )
<type ‘tuple‘>
>>> 

3，向集合添加一个值，删除一个值，求交集和并集

>>> a
set([‘a‘, ‘c‘, ‘b‘, ‘e‘, ‘d‘, ‘g‘, ‘f‘])
>>> a.add( ‘ghostwu‘ )
>>> a
set([‘a‘, ‘c‘, ‘b‘, ‘e‘, ‘d‘, ‘g‘, ‘f‘, ‘ghostwu‘])
>>> a.remove( ‘g‘ )
>>> a
set([‘a‘, ‘c‘, ‘b‘, ‘e‘, ‘d‘, ‘f‘, ‘ghostwu‘])
>>> b = set( "abcdlmn" )
>>> a & b
set([‘a‘, ‘c‘, ‘b‘, ‘d‘])
>>> a | b
set([‘a‘, ‘c‘, ‘b‘, ‘e‘, ‘d‘, ‘f‘, ‘m‘, ‘l‘, ‘n‘, ‘ghostwu‘])
>>> 

4，用字典实现一个学生成绩小系统，之后进行添加，修改，删除，排序等操作

>>> student = { ‘ghostwu‘ : { ‘name‘ : ‘ghostwu‘, ‘age‘ : 20, ‘score‘ : { ‘math‘ : 78, ‘english‘ : 66, ‘python‘ : 75 } } }
>>> student
{‘ghostwu‘: {‘age‘: 20, ‘score‘: {‘python‘: 75, ‘math‘: 78, ‘english‘: 66}, ‘name‘: ‘ghostwu‘}}
>>> student[‘tom‘] = { ‘name‘ : ‘tom‘, ‘age‘ : 21, ‘score‘ : { ‘math‘ : 60, ‘english‘ : 80, ‘python‘ : 90 } }
>>> student
{‘ghostwu‘: {‘age‘: 20, ‘score‘: {‘python‘: 75, ‘math‘: 78, ‘english‘: 66}, ‘name‘: ‘ghostwu‘}, ‘tom‘: {‘age‘: 21, ‘score‘: {‘python‘: 90, ‘math‘: 60, ‘english‘: 80}, ‘name‘: ‘tom‘}}
>>> student[‘ghostwu‘][‘score‘][‘php‘] = 90
>>> student[‘tom‘][‘score‘][‘php‘] = 50
>>> student[‘ghostwu‘][‘score‘][‘math‘] = 30
>>> del student[‘ghostwu‘][‘age‘]
>>> score1 = student[‘ghostwu‘][‘score‘].values()
>>> score1
[75, 90, 30, 66]
>>> score1.sort()
>>> score1
[30, 66, 75, 90]
>>> student.pop( ‘address‘, ‘shenzhen‘ )
‘shenzhen‘
>>> student
{‘ghostwu‘: {‘score‘: {‘python‘: 75, ‘php‘: 90, ‘math‘: 30, ‘english‘: 66}, ‘name‘: ‘ghostwu‘}, ‘tom‘: {‘age‘: 21, ‘score‘: {‘python‘: 90, ‘php‘: 50, ‘math‘: 60, ‘english‘: 80}, ‘name‘: ‘tom‘}}
>>>