[2025sl93041-gkb]

Problem

dehumanize() gives wrong results for any fractional input. For example:

arw = arrow.Arrow(2026, 1, 1, tzinfo="UTC")
arw.dehumanize("1.5 hours ago")   # returns 2025-12-31T19:00:00+00:00  (−5 h, wrong)
arw.dehumanize("0.5 days ago")    # returns 2025-12-27T00:00:00+00:00  (−5 days, wrong)

Expected: −1.5 h and −0.5 days respectively. No exception is raised — the result is just quietly wrong.

Reported in #1341.

Root Cause

The number-matching regex r"\d+" only matches whole digit sequences. For an input like "1.5 hours ago":

• re.compile(r"\d+").search("1.5 hours ago") returns "1" (stops at the decimal point)
• The .5 is then matched on its own as 5 in the timeframe search

Both matches write to the same time_object_info["hours"] key, but the second match overwrites the first with 5, giving a shift of -5 hours.

Fix

Three changes to dehumanize() in arrow/arrow.py:

1. Change num_pattern from r"\d+" to r"\d+(?:\.\d+)?" so the decimal part is captured as one token.
2. Change the per-timeframe search_string.format(r"\d+") to use the same decimal-aware pattern so locale timeframe patterns also match fractional values.
3. Switch time_object_info initial values and all int() casts to float so the fractional amount is preserved through to shift().

Testing

Added test_fractional_units to tests/test_arrow.py covering hours, days, and weeks in both past and future directions. Full suite: 1903 passed, 1 warning.

def test_fractional_units(self):
    arw = arrow.Arrow(2026, 1, 1, tzinfo="UTC")
    assert arw.dehumanize("1.5 hours ago") == arw.shift(hours=-1.5)
    assert arw.dehumanize("0.5 days ago") == arw.shift(days=-0.5)
    assert arw.dehumanize("in 1.5 hours") == arw.shift(hours=1.5)
    assert arw.dehumanize("2.5 weeks ago") == arw.shift(weeks=-2.5)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (2224255) to head (099114c).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff            @@
##            master     #1406   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files           10        10           
  Lines         2315      2315           
  Branches       358       358           
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  Hits          2315      2315           

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