difflib.SequenceMatcher.get_opcodes

[DomoticaVirginia]

Bug report

Bug description:

from difflib import SequenceMatcher
a = "qabxwzcd"
b = "abycdf"
s = SequenceMatcher(None, a, b)
for tag, i1, i2, j1, j2 in s.get_opcodes():
    print('{:7}   a[{}:{}] --> b[{}:{}] {!r:>8} --> {!r}'.format(tag, i1, i2, j1, j2, a[i1:i2], b[j1:j2]))

This is the output:

delete    a[0:1] --> b[0:0]      'q' --> ''
equal     a[1:3] --> b[0:2]     'ab' --> 'ab'
replace   a[3:4] --> b[2:3]      'x' --> 'y'
equal     a[4:6] --> b[3:5]     'wz' --> 'cd'
insert    a[6:6] --> b[5:6]       '' --> 'f'

In the penultimate line - the one with the equal tag - it is 'wz' --> 'cd'?

Thank you very much

CPython versions tested on:

3.13

Operating systems tested on:

Windows

[efimov-mikhail]

Thanks for the report! But your output seems weird for me:

-> % cat difflib_bug.py                             
from difflib import SequenceMatcher
a = "qabxwzcd"
b = "abycdf"
s = SequenceMatcher(None, a, b)
for tag, i1, i2, j1, j2 in s.get_opcodes():
    print('{:7}   a[{}:{}] --> b[{}:{}] {!r:>8} --> {!r}'.format(tag, i1, i2, j1, j2, a[i1:i2], b[j1:j2]))

-> % uv tool run --python 3.13 python difflib_bug.py
delete    a[0:1] --> b[0:0]      'q' --> ''
equal     a[1:3] --> b[0:2]     'ab' --> 'ab'
replace   a[3:6] --> b[2:3]    'xwz' --> 'y'
equal     a[6:8] --> b[3:5]     'cd' --> 'cd'
insert    a[8:8] --> b[5:6]       '' --> 'f'

[DomoticaVirginia]

I apologize. It was due to a display error in the VS Code terminal when expanding it.

Thanks again

[efimov-mikhail]

No worry, everything is okay. Have a good day!