Python: Find specific sum of values?

Question

I am trying to find the sum of to values from a text file that is equal to 2020 with python. The text file contains multiple numbers each written in one line like this:

What is the easiest and fastest way to do this in python?

My code reads in the file correctly but does not access the inner for loop?

data = []
try:
    file = open('/Users/korbinianschleifer/desktop/input.txt', 'r+')
    data = file.readlines()
    file.close()
except x:
    print('file could not be loaded')

print(len(data))

for i in range(len(data)):
    for j in range(i+1,len(data)):
        if data[i]+data[j] == 2020: 
            print('solution found')

Does this answer your question? Two Sum on LeetCode

sahasrara62
– sahasrara62

2020-12-09 15:20:45 +00:00
Commented Dec 9, 2020 at 15:20 — sahasrara62
– sahasrara62, Commented Dec 9, 2020 at 15:20

Aplet123 · Accepted Answer · 2020-12-09 15:16:11Z

Your data list is a list of strings, which means + will concatenate them ("1" + "1" is "11"), which is not the behavior you want. Parse your data to an int:

# use with to avoid having to close the file manually
with open('/Users/korbinianschleifer/desktop/input.txt', 'r+') as file:
    data = file.readlines()

# parse it to an int
data = [int(x) for x in data]

for i in range(len(data)):
    for j in range(i + 1, len(data)):
        if data[i] + data[j] == 2020:
            print("solution found", data[i], data[j])

As a side note, the faster way to do this is to maintain a set of values:

# use with to avoid having to close the file manually
with open('/Users/korbinianschleifer/desktop/input.txt', 'r+') as file:
    data = file.readlines()

# parse it to an int
data = [int(x) for x in data]

seen = set()
for v in data:
    if 2020 - v in seen:
        print("solution found", v, 2020 - v)
    seen.add(v)

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