I don't know how to decrement from an object in a list.

For example:

a = 1
b = 2
c = 3
lst = [a, b, c]
choice = a
choice = choice - 2

When I do that it doesn't deduct from a

CodePudding user response：

You use indexing to access list elements:

a = 1
b = 2
c = 3
list = [a, b, c]
choice = 0 # the index of `a`
lst[choice] -= 2

This won't change the value of a because integers are immutable in python. Only the reference stored in the list will change.

You can find the index by value using list.index:

choice = lst.index(a)

If you want to search by name instead of by value, use a dictionary instead of a list:

d = {
    'a' = 1,
    'b' = 2,
    'c' = 3
}
d['a'] -= 2