partial_ratio_alignment giving wrong index values

[sroy-forr]

partial_ratio_alignment giving wrong index values for source when the destination match is longer than the source match.

s1 = "a certain string"; s2 = "certainly"; res = fuzz.partial_ratio_alignment(s1, s2); print(res);
Output: ScoreAlignment(score=77.77777777777779, src_start=0, src_end=9, dest_start=0, dest_end=9)

Notice the src is (0, 9) instead of (1, 8).

Is this an expected behaviour?

[maxbachmann]

fuzz.partial_ratio is using a sliding window of len(shorter_string) to determine the optimal alignment. fuzz.partial_ratio_alignment returns the indexes of one alignment which results in the optimal score.
In your example the optimal alignment found this way is: "a certain" <-> "certainly".