BUG: 'Unnamed' != unnamed column in CSV

[gfyoung]

False criterion was causing errors when specified headers appeared to capture
a seemingly unnamed row, just because they had the string "Unnamed" in it.

Setup:

from pandas import read_csv
from pandas.compat import StringIO

data = "Unnamed,NotUnnamed\n0,1\n2,3\n4,5"
read_csv(StringIO(data), header=[0, 1])

Previously, this would error:

...
ValueError : Passed header=[0,1] are too many rows for this multi_index of columns

Now, it nicely returns a DataFrame:

  Unnamed NotUnnamed
        0          1
0       2          3
1       4          5

Leverages the patch used in #23484 of self.unnamed_cols.

[pep8speaks]

Hello @gfyoung! Thanks for submitting the PR.

• There are no PEP8 issues in the file pandas/io/parsers.py !

• There are no PEP8 issues in the file pandas/tests/io/parser/header.py !

[codecov]

Codecov Report

Merging #23687 into master will decrease coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master   #23687      +/-   ##
==========================================
- Coverage   92.25%   92.25%   -0.01%     
==========================================
  Files         161      161              
  Lines       51383    51381       -2     
==========================================
- Hits        47404    47402       -2     
  Misses       3979     3979

Flag	Coverage Δ
#multiple	90.64% <100%> (-0.01%)	⬇️
#single	42.32% <0%> (ø)	⬆️

Impacted Files	Coverage Δ
pandas/io/parsers.py	95.54% <100%> (-0.01%)	⬇️

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[gfyoung]

@jreback : Address the comment, and all is still green. PTAL.

[jreback]

conflict in the whatsnew, can you merge master

[gfyoung]

@jreback : Rebased my changes, and all is green. PTAL.

[gfyoung]

@jreback : Addressed all comments, all is still green. PTAL.

[jreback]

thanks!

[SamLevinSE]

I'm getting bunch of these "unnamed ..." where my column is empty. Is this related to the same bug?
ex:

Unnamed: 1_level_0	Baseline Features	Unnamed: 3_level_0	Unnamed: 4_level_0	Unnamed: 5_level_0	Unnamed: 6_level_0	Unnamed: 7_level_0

[gfyoung]

@SamLevinSE : I don't believe so. However, if you are welcome to open a new issue to provide more details, as it could still be a problem with pandas (can't tell from this).

[SamLevinSE]

@gfyoung What if I give you some more Information? could you please check these two screenshots and let me know if I need to create a new bug/issue or if I'm doing something wrong?

Thank you!

[gfyoung]

This looks expected as far as I can see.