Repository navigation
ndiff intraline miss #161152
Description
Bug report
I happened to be using icdiff and noticed it matched a whole line, not just the different comments. There's something about the text (Japanese in this instance) that's causing an intraline change to be missed. Here's a simple test program:
import difflib
import sys
text1 = ["common の\n"]
text2 = ["common no\n"]
sys.stdout.writelines(difflib.ndiff(text1, text2))
text1 = ["common のの\n"]
text2 = ["common non\n"]
sys.stdout.writelines(difflib.ndiff(text1, text2))
text1 = ["common のの\n"]
text2 = ["common nono\n"]
sys.stdout.writelines(difflib.ndiff(text1, text2))and its output:
- common の
? ^
+ common no
? ^^
- common のの
? ^^
+ common non
? ^^^
- common のの
+ common nono
As you can see, the first two intraline differences were found, but not the last.
Not important (for my purposes I want whole-line differences, anyway), but worth mentioning.
CPython versions tested on:
3.12, 3.15
Operating systems tested on:
Windows
Activity
gvanrossum commentedon Nov 2, 2026
Ah. There's an internal limit for how much the lines can differ for the intra-line markers to be displayed. Your example appears to score just above the limit. I think adjusting the limit would be tricky -- it would probably break existing code that somehow relies on the current limit. I don't see a compelling reason to bother, so I'm closing this issue. Thanks for paying attention!
PS. The cutoff is hardcoded on line 925 to be 0.74999. There's a long comment explaining its purpose before that.