Question :
I would like to compare two text files which have three columns each. One file has 999 rows and another has 757 rows. I want the different 242 rows to be stored in a different file. I created the first file (999 rows) using a random network generator (999 rows are edges with third column being weight between first, second columns – source, destination nodes).
File Format – Files 1, 2
1 3 1
16 36 1
I have tried
Compare two files line by line and generate the difference in another file
and
find difference between two text files with one item per line and http://www.daniweb.com/software-development/python/threads/124932/610058#post610058
Neither worked for me.
I think it is a problem of string comparison. I would like to compare the numbers in first column and second column. If they both are different, I want to write it to third file.
Any help will be much appreciated!
Update
I am posting the following code that I tried after @MK posted his comment.
f = open("results.txt","w")
for line in file("100rwsnMore.txt"):
rwsncount += 1
line = line.split()
src = line[0]
dest = line[1]
for row in file("100rwsnDeleted.txt"):
row = row.split()
s = row[0]
d = row[1]
if(s != src and d != dest):
f.write(str(s))
f.write(' ')
f.write(str(d))
f.write('n')
f.close()
Answer #1:
The best general-purpose option if you’re on a *nix system is just to use:
sort filea fileb | uniq -u
But if you need to use Python:
Your code reopens the inner file in every iteration of the outer file. Open it outside the loop.
Using a nested loop is less efficient than looping over the first storing the found values, and then comparing the second to those values.
def build_set(filename):
# A set stores a collection of unique items. Both adding items and searching for them
# are quick, so it's perfect for this application.
found = set()
with open(filename) as f:
for line in f:
# [:2] gives us the first two elements of the list.
# Tuples, unlike lists, cannot be changed, which is a requirement for anything
# being stored in a set.
found.add(tuple(sorted(line.split()[:2])))
return found
set_more = build_set('100rwsnMore.txt')
set_del = build_set('100rwsnDeleted.txt')
with open('results.txt', 'w') as out_file:
# Using with to open files ensures that they are properly closed, even if the code
# raises an exception.
for res in (set_more - set_del):
# The - computes the elements in set_more not in set_del.
out_file.write(" ".join(res) + "n")
