Problem with Pandas query function not evaluating/subsetting correctly

Question

Why does df.query("ColumnB > '6'") evaluate to the second row of the dataframe only? Expected answer was second to fifth row because those are rows where the values in Column B are greater than 6.

Ideally for that comparison to work, ColumnB should be of type int or float. So you might want to remove quotes from 6. Should be: df.query("ColumnB > 6") — Mayank Porwal
– Mayank Porwal, Commented May 23, 2020 at 12:34
You can also try doing df[df['ColumnB'] > 6]. Check if this gets you the right result. — Mayank Porwal
– Mayank Porwal, Commented May 23, 2020 at 12:36
Thank you for pointing that out. However when I unquote 6, I get a type error. TypeError: '>' not supported between instances of 'str' and 'int' As a side note, although I'm aware this can be done through boolean indexing, I am currently exploring ways how to filter data with the query function specifically. Any ideas how to make it evaluate correctly? — mars_
– mars_, Commented May 23, 2020 at 12:39
Do this: df['ColumnB'] = df['ColumnB'].astype(int) and then run df.query("ColumnB > 6"). — Mayank Porwal
– Mayank Porwal, Commented May 23, 2020 at 12:44

Mayank Porwal · Accepted Answer · 2020-05-23 12:52:44Z

1

You need to convert ColumnB into int:

df['ColumnB'] = df['ColumnB'].astype(int)
df.query("ColumnB > 6")

answered May 23, 2020 at 12:52

Mayank Porwal

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