python : Compare two large files
I want to show different number of lines after comparing two files. You want to display a different number of message lines after the program completes.
with open(file2) as b: blines = set(b) with open(file1) as a: with open(file3, 'w') as result: for line in a: if line not in blines: result.write(line) lines_to_write =  with open(file2) as b: blines = set(b) with open(file1) as a: lines_to_write = [l for l in a if l not in blines] print('count of lines are in difference:', len(lines_to_write))
If you can load everything into memory, you can do the following on the collection:
union = set(alines).union(blines) intersection = set(alines).intersection(blines) unique = union - intersection
EDIT: It’s simpler (and faster) to: