用 python 中的新元素 using.remove() 和.append() 替换子列表元素之一

Question

subjects = ["Algorithms", "Software Design", "Poetry", "Electronics"] 
grades = ["98", "88", "85", "90"]
print("Course  ", "  Score")
gradebook = zip(subjects, grades)
for subject, grade in gradebook: #for creating a table
    print(subject, '\t', grade)
print('\n')
grade_book = list(gradebook)
list(grade_book[2]).remove('85')
list(grade_book[2]).append('Pass')

Here I have a sublist as ['Poetry', '85'], and I have to delete the grade(85) by using remove() and by using the.append() add a new "Pass" value to the sublist where the 85 is located. I tried it in the last two lines, but it didn't work out.

Answer 1

zip return a list of tuple. Once a tuple is created, you cannot change its values.

1. create a new tuple, and replace it
2. turn it to a list, change, re-tuple it

Answer 2

You can convert the list of tuples into a list of lists instead and the edit

grade_book = [list(elem) for elem in gradebook]
grade_book[2][1] = 'Pass'

If you need to convert back to a list of tuples you can do so like this

grade_book = [(x,y) for [x,y] in grade_book]

A dictionary might also be a nice option here.

Answer 3

zip(subjects, grades) returns an iterator. By looping through gradebook you already "use up" all the values in the iterator. That's why grade_book = list(gradebook) returns an empty list, thus making the following operations invalid.

I would also suggest to use a dictionary here, like so:

subjects = ["Algorithms", "Software Design", "Poetry", "Electronics"] 
grades = ["98", "88", "85", "90"]
gradebook = dict(zip(subjects, grades))
print("Course  ", "  Score")
for subject, grade in gradebook.items(): # for creating a table
    print(subject, '\t', grade)
print()

Then you can easily add new elements and use.pop() to remove elements:

gradebook.pop('Poetry')
gradebook["Pass"] = "85"