Given file.txt:

a b c 

And this patch (my.diff):

--- file.txt +++ file.txt @@ -1,3 +1,4 @@ a b +b1 d 

Which is applied using:

import patch p = patch.fromfile("my.diff") p.apply(".")

file.txt now looks like this:

a b b1 d 

The patch only adds b1 but the following context was also put into the file. After applying the patch file.txt should not contain d but end with c.