How to compare two files in Python and add missing elements?

Question

Python

Good day.
There are two files. First 1.csv:

template1;NEW;1000
template2;OLD;1010
template3;OLD;1020
template4;OLD;1000

Second 2.csv:

template1;OLD;1000
template2;NEW;1030
template5;OLD;1020
template6;OLD;1010

I try with this script

b = []
for tom in open('1.csv', 'r'):
    tom1, tom2, tom3 = tom.split(';')
    for fin in open('2.csv', 'r'):
        fin1, fin2, fin3 = fin.split(';')

        if tom1 == fin1 and tom2 == fin2:
            b.append(tom1 + ';' + tom2 + ';' + str(int(tom3) + 1) + '\n')
            break
        elif tom1 == fin1 and tom2 != fin2:
            b.append(tom1 + ';' + fin2 + ';1000\n')
            break

for i in b:
    print(i)

do a merge of two files, outputs

template1;OLD;1000
template2;NEW;1000

if I add one more condition

elif tom1 != fin1 and tom2 != fin2:
            b.append(fin1 + ';' + fin2 + ';1000\n')
            break

get

template1;OLD;1000

template2;NEW;1000

template2;NEW;1000

template2;NEW;1000

Can you please tell me how to process these two files so that all records missing in the first file end up in the second?

Answer 1

I will add. UPDATE: so short

result = {}
for tom in open('k1.csv', 'r'):
    t1, t2, t3 = tom.replace('\n', '').split(';')
    result[t1] = (t2, t3)

for tom in open('k2.csv', 'r'):
    t1, t2, t3 = tom.replace('\n', '').split(';')
    if t1 not in result.keys():
        result[t1] = (t2, t3)

for k in result.keys():
    print('{}: {}'.format(k, result[k]))

Job in progress

Answer 2

Should work

template1;NEW;1000
template2;OLD;1010
template3;OLD;1020
template4;OLD;1000
template5;OLD;1020
template6;OLD;1010

those. everything that was missing in the first file should be added from the second.

Answer 3

for line in open("file2"):
    if line not in open("file1"):
        open("file1","a").write(line)

Answer 4

And there are also wonderful batteries
https://docs.python.org/2/library/difflib.html