Fixes example code in docstring of pandas.DataFrame.query

[alphaCTzo7G]

• closes Error in docstring for pandas/core/frame.py #21733
• tests added / passed
• passes git diff upstream/master -u -- "*.py" | flake8 --diff
• whatsnew entry

[jreback]

ahh these are the old forms, can you rather amend to

import numpy as np
import pandas as pd

then change the randn call

[alphaCTzo7G]

@jreback Ok.. I changed it as follows..

    >>> import numpy as np
    >>> import pandas as pd
    >>> df = pd.DataFrame(np.random.randn(10, 2), columns=list('ab'))
    >>> df.query('a > b')
    >>> df[df.a > df.b]  # same result as the previous expression

I force pushed it to the same branch..

https://github.com/alphaCTzo7G/pandas/tree/fix_typo_query

I noticed there are some other docstrings with from pandas or from numpy..

./pandas/plotting/_converter.py|134 col 17| ">>> from pandas.plotting import register_matplotlib_converters"
./pandas/plotting/_misc.py|501 col 5| >>> from pandas import read_csv
./pandas/plotting/_misc.py|502 col 5| >>> from pandas.tools.plotting import parallel_coordinates
./pandas/util/testing.py|602 col 5| >>> from pandas.util.testing import capture_stdout
./pandas/util/testing.py|650 col 5| >>> from pandas.util.testing import capture_stderr
./pandas/util/testing.py|2213 col 7| >>> from pandas.util.testing import network
./pandas/util/testing.py|2214 col 7| >>> from pandas.io.common import urlopen
./pandas/tseries/holiday.py|145 col 9| >>> from pandas.tseries.holiday import Holiday, nearest_workday
./pandas/tseries/holiday.py|146 col 9| >>> from pandas import DateOffset
pandas/core/sparse/series.py|739 col 9| >>> from numpy import nan
pandas/core/algorithms.py|1519 col 5| >>> from pandas.api.extensions import take
pandas/core/dtypes/concat.py|285 col 5| >>> from pandas.api.types import union_categoricals
./pandas/io/pytables.py|457 col 5| >>> from pandas import DataFrame
./pandas/io/pytables.py|458 col 5| >>> from numpy.random import randn
./pandas/io/json/normalize.py|138 col 5| >>> from pandas.io.json import json_normalize
./pandas/io/stata.py|2713 col 5| >>> from pandas.io.stata import StataWriter117

Do these need to be adjusted as well?

[gfyoung]

Probably, but don't fix them here. Would do in a separate PR.

[alphaCTzo7G]

Ok.. I will create 1 PR to fix the rest of them.

[codecov]

Codecov Report

Merging #21731 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #21731   +/-   ##
=======================================
  Coverage   91.92%   91.92%           
=======================================
  Files         158      158           
  Lines       49705    49705           
=======================================
  Hits        45693    45693           
  Misses       4012     4012

Flag	Coverage Δ
#multiple	90.3% <ø> (ø)	⬆️
#single	41.99% <ø> (ø)	⬆️

Impacted Files	Coverage Δ
pandas/core/frame.py	97.19% <ø> (ø)	⬆️

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[gfyoung]

LGTM!

cc @jreback

[jreback]

thanks @alphaCTzo7G