BUG: index_col in read_csv ignores dtype argument about pandas

[xouyang1]

take

[xouyang1]

Seems to be a behavior change for the default c engine only.
python engine is also incorrect (returning int64) but was also doing that in v2.2.2

[MarcoGorelli]

thanks for the report - we should probably first do a git bisect to see which commit introduced the bug

running it now: https://www.kaggle.com/code/marcogorelli/pandas-regression-example?scriptVersionId=187955574

[xouyang1]

@MarcoGorelli Hi Marco, I tried rerunning the regression example with just data = io.StringIO("345.5 519.5 0) and it always lands at the latest commit, which is incorrect. Can you help take a look?

[MarcoGorelli]

thanks @xouyang1 - I was missing an escape character in the script, and so it wasn't running properly

having tried again, I'm getting #57943 as the commit that introduced it, but I don't know if that seems reasonable, haven't looked closer yet

[xouyang1]

thanks @xouyang1 - I was missing an escape character in the script, and so it wasn't running properly

having tried again, I'm getting #57943 as the commit that introduced it, but I don't know if that seems reasonable, haven't looked closer yet

It looks like the right commit, specifically this change to pandas/core/indexes/base.py ded256d#diff-c34a28314fc8cb12f0d2aa710f1c15f06cdfe3e48f03e658f01f99a43d4f5d09

• Before: does not convert to range (np_sequence.dtype.kind is “u” for uint so returns the sequence as is)

  pandas/pandas/core/indexes/base.py

  Line 7164 in cf40e56

  return sequence

• After: converts to range, which drops the dtype association

  pandas/pandas/core/indexes/base.py

  Line 7170 in ded256d

  return range(sequence[0], sequence[-1] + diff, diff)

[MarcoGorelli]

It looks like the right commit, specifically this change to pandas/core/indexes/base.py ded256d#diff-c34a28314fc8cb12f0d2aa710f1c15f06cdfe3e48f03e658f01f99a43d4f5d09

cool, thanks for checking (cc @mroeschke just fyi, no blame 🤗 )