KeyError in Pandas sort_values

Question

I am trying to sort a dataframe by a particular column: "Lat". However, although when I print out the column names, "Lat" clearly shows up, when I try to use it as the "by" parameter in the sort_values function, I get a KeyError. It doesn't matter which column name I use, I get a key error no matter what.

I have tried using different columns, running in place, stripping the columns names, nothing seems to work

print(lights_df.columns.tolist())
lights_by_lat = lights_df.sort_values(axis = 'columns', by = "Lat", kind 
= "mergesort")

outputs:

['the_geom', 'OBJECTID', 'TYPE', 'Lat', 'Long']

KeyError: 'Lat'

^output from trying to sort

want axis='index' (or just leave it out since it's the default) — ALollz
– ALollz, Commented Jul 23, 2019 at 17:53
The confusion here is because for sort, axis specifies the axis to be sorted. You are using a column to change the ordering of rows, so axis='index' is what's needed. With a better minimal reproducible example maybe it would be worth an answer. — ALollz
– ALollz, Commented Jul 23, 2019 at 18:01

skhan · Accepted Answer · 2019-07-23 17:57:08Z

7

All you have to do is remove the axis argument:

lights_by_lat = lights_df.sort_values(by = "Lat", kind = "mergesort")

and you should be good.

answered Jul 23, 2019 at 17:57

skhan

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robertspierre Over a year ago

See @ALollz comment on OP post for the explanation

matt · Accepted Answer · 2023-08-24 01:34:41Z

1

I think it's because you are seeking on the wrong axis. For example, this dataframe:

Let's say: I want to order by the row axis with label "1". So you put this:

df.sort_values(by='1',axis=0,inplace=False)

But the result give the error: KeyError: '1'

The solution is changing the axis to columns:

df.sort_values(by='1',axis=1,inplace=False)

I think it's because you want to order by row label "1" data, but the axis is "index", so ordering by "1" label is not possible because numbers are reordered in the column axis and not the index axis.

I hope this helps others.

answered Aug 24, 2023 at 1:34

matt

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