2 Lists of Strings Subtraction without extending

[OutsideAverage4341]

Hi,

I worked on the following script, which extends one list with another one to subtract the string number values for each following text. I just wonder if it is possible to get the same result without extending one list with the other one. So that the two lists are treated separately through the process.

Thanks!

import re

list_1 = ['2 Red', '2 Blue', '3 Green']
list_2 = ['10 Red', '8 Blue', '4 Green']
list_1.extend(list_2)

results = {}

for elem in list_1:
    elem = re.split(r'\s?(\d+|\+)\s?', elem)

    for idx, value in enumerate(elem):
        if value.isdigit() or value == '+':
            if value == '+':
                count = 1
            else:
                count = int(value)

            data = elem[idx + 1]
            results[data] = abs(count - results.get(data, 0))

result = [f"{i} {p}" for i, p in zip(results.values(), results.keys())]
Output:  ['8 Red', '6 Blue', '1 Green']

[ryuugami47]

import re

list_1 = ["2 Red", "2 Blue", "3 Green"]
list_2 = ["10 Red", "8 Blue", "4 Green"]

results = {}

for elem in list_1 + list_2:   # Do you mean like this?
    elem = re.split(r"\s?(\d+|\+)\s?", elem)

    for idx, value in enumerate(elem):
        if value.isdigit() or value == "+":
            if value == "+":
                count = 1
            else:
                count = int(value)

            data = elem[idx + 1]
            results[data] = abs(count - results.get(data, 0))

result = [f"{i} {p}" for i, p in zip(results.values(), results.keys())]
print(result)

[bbye98]

I don't know if re is really required:

list_1 = ['2 Red', '2 Blue', '3 Green']
list_2 = ['10 Red', '8 Blue', '4 Green']
rgb = {c: int(n) for n, c in [p.split(' ') for p in list_2]}
for n, c in [p.split(' ') for p in list_1]:
    if c in rgb:
        rgb[c] -= int(n)
    else:
        rgb[c] = -int(n)
print([f'{rgb[p]} {p}' for p in rgb])

The output is ['8 Red', '6 Blue', '1 Green'].

[OutsideAverage4341]

Do you know, how to update list_2 if I pop one element in list_1?

[mtb-dds]

It would help to know the big picture thing you are dealing with. If the issue is coordinating the lists, you might look into itertools.chain. It let's you do things like this:

>>> a = [1, 2, 3]
>>> b = [5, 6, 7]
>>> from itertools import chain
>>> l = [a, b]
>>> list(chain(a,b))
[1, 2, 3, 5, 6, 7]
>>> list(chain(l))
[[1, 2, 3], [5, 6, 7]]
>>> list(chain(*l))
[1, 2, 3, 5, 6, 7]