如何解决为什么出现在 Pandas 中的 KeyError

Question

I'm using Pandas to process the Dataframe, I need to use the Date column to create additional columns:

I have filtered the Date column to get 2022/2021 information only using:

df = df.loc[df["Date"].between("2022", "2021")]

Currently I have:

Date	Type	Initial	Number
2022	Bin	S	5
2022	Bin	S	6
2022	Bin	S	9
2021	Bin	B	5
2021	Bin	B	7
2021	Bin	B	0

I am currently trying to get the following output:

Type	2022	2021	Initial	Difference
Bin	20	12	S/B	8

Following the process to create the bottom table, I have come across the following error

df = df.loc[df["Date"].between("2022", "2021")]
dfx = df.groupby(['Type ','Date ']).agg({'Initial ':lambda x: '/'.join([str(r) for r in x.unique()]),'Number':'sum'}).reset_index()
dfy = dfx.pivot(index=['Type ','Initial '], columns='Date ', values='Number').reset_index()

but I keep receiving the following error message:

  raise KeyError(key) from err
KeyError: 'Date'

Answer 1

The KeyError: 'Date' doesn't have a space in it. this is the only line I see where Data doesn't have a trailing space.

df = df.loc[df["Date"].between("2022", "2021")]

Try adding a trailing space and see what happens:

df = df.loc[df["Date "].between("2022", "2021")]

Like @topsail says, trailing spaces in column names are a recipe for errors,