dc_fast_search.py

with open('input_pairs.txt') as f:
    ids = {}
    lines = f.readlines()
    for line in lines:
        p,q = [int(x) for x in line.split(' ')]
        if p not in ids:
            ids[p] = p
        if q not in ids:
            ids[q] = q
        if ids[p] == ids[q]:
            continue
        t = ids[p]
        for key in ids:
            if ids[key] == t:
                ids[key] = ids[q]
        print(p,q)