Python - 从一个 class 获取列表/字典，在另一个 class 中进行修改并将修改值返回给第一个 ZA2F2ED4F8EBC26BBCB1

Question

first.py

class A():
    lst = [2,2,1]

second.py

from first import A
class B():
    new_lst = A.lst
    new_lst.remove(1)
    #new_lst = [2,2]

Now how can i update new_list value from class B to class A so that class A, lst=[2,2]

Please help me out.

Answer 1

I wrote this as a comment at first, but I might as well write a complete answer for it. When you call new_lst = A.lst you're not actually copying the values inside of A.lst . What's happening is that you're creating a pointer to the variable inside of A .

We can demonstrate this by adding a couple of lines inside of second.py :

from first import A
class B:
    new_lst = A.lst

print(f'A: {A.lst}, B: {B.new_lst}') #Output: A: [1, 2, 3], B: [1, 2, 3]
B.new_lst.append("testing")
print(f'A: {A.lst}, B: {B.new_lst}') #Output: A: [1, 2, 3, 'testing'], B: [1, 2, 3, 'testing']
A.lst.remove(3)
print(f'A: {A.lst}, B: {B.new_lst}') #Output: A: [1, 2, 'testing'], B: [1, 2, 'testing']

As you can see, if we add a new variable to B.new_lst it's also added to A.lst likewise when we remove a value from A.lst .