迭代字典,添加键和值

Question

我想迭代一本字典,每次修改字典而不是当前正在发生的字典,而是用新的字符重置旧值.

我目前的代码是:

while True:
    grades = { raw_input('Please enter the module ID: '):raw_input('Please enter the grade for the module: ') }

但是,这不会修改列表,而是删除以前的值.我该如何修改字典呢？

(另外,当我运行它时,它希望我在键之前输入值,为什么会发生这种情况？)

Answer 1

在您的示例中,每次使用新的键值对更新成绩(字典).

>>> grades = { 'k':'x'}
>>> grades
{'k': 'x'}
>>> grades = { 'newinput':'newval'}
>>> grades
{'newinput': 'newval'}
>>> 

你应该做的是更新同一个dict的键值对:

>>> grades = {}
>>> grades['k'] = 'x'
>>> grades['newinput'] = 'newval'
>>> grades
{'k': 'x', 'newinput': 'newval'}
>>> 

试试这个:

>>> grades = {}
>>> while True:
...     k = raw_input('Please enter the module ID: ')
...     val = raw_input('Please enter the grade for the module: ')
...     grades[k] = val
... 
Please enter the module ID: x
Please enter the grade for the module: 222
Please enter the module ID: y
Please enter the grade for the module: 234
Please enter the module ID: z
Please enter the grade for the module: 456
Please enter the module ID: 
Please enter the grade for the module: 
Please enter the module ID: Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
KeyboardInterrupt
>>> 
>>> grades
{'y': '234', 'x': '222', 'z': '456', '': ''}
>>>