用另一个列表中的项目替换列表中的项目

Question

I'm trying to create a calculator for a User's weighted GPA. I'm using PyautoGUI to ask the user for their grades and type of class they're taking. But I want to be able to take that User input and essentially remap it to a different value.

class GPA():
    grades = []
    classtypes = []

    your_format = confirm(text='Choose your grade format: ', title='', 
    buttons=['LETTERS', 'PERCENTAGE', 'QUIT'])

    classnum = int(prompt("Enter the number of classes you have: "))

    for i in range(classnum):
        grade = prompt(text='Enter your grade for the course 
:'.format(name)).lower()
    classtype = prompt(text='Enter the type of Course (Ex. Regular, AP, Honors): ').lower()

    classtypes.append(classtype)
    grades.append(grade)

    def __init__(self):
        self.gradeMap = {'a+': 4.0, 'a': 4.0, 'a-': 3.7, 'b+': 3.3, 'b': 3.0,'b-': 2.7,
         'c+': 2.3, 'c': 2.0, 'c-': 1.7, 'd+': 1.3, 'd': 1.0, 'f': 0.0}
        self.weightMap = {'advanced placement': 1.0, 'ap': 1.0, 'honors': 0.5,'regular': 0.0}

Answer 1

Based on the gradeMap dictionary you have defined you could do something with what's called a list comprehension .

An example of what I'm talking about done using the Python interpreter:

>>> grades = ['a', 'c-', 'c']
>>> gradeMap = {'a+': 4.0, 'a': 4.0, 'a-': 3.7, 'b+': 3.3, 'b': 3.0,'b-': 2.7,
...             'c+': 2.3, 'c': 2.0, 'c-': 1.7, 'd+': 1.3, 'd': 1.0, 'f': 0.0}
>>> [gradeMap[grade] for grade in grades] #here's the list comprehension
[4.0, 1.7, 2.0]

I think the downside with this approach might be making sure the user only gives you a grade you have defined in your gradeMap otherwise it is going to give you a KeyError .

Another alternative would be to use map . map is slightly different in that it expects a function and an input list, and then applys that function over the input list.

An example with a very simple function that only works with a few grades:

>>> def convert_grade_to_points(grade):
...   if grade == 'a':
...     return 4.0
...   elif grade == 'b':
...     return 3.0
...   else:
...     return 0
... 
>>> grades = ['a', 'b', 'b']
>>> map(convert_grade_to_points, grades)
[4.0, 3.0, 3.0]

This also suffers from the downside I mentioned earlier that the function you define has to handle the case where the user input an invalid grade.

Answer 2

You can replace items of the list in place.

for grade in gradeList:
    if type is "PERCENTAGE":
       grade = grade × some_factor  # use your logic
    elif type is "LETTERS":
       grade="some other logic"