CODEWITHSUNDEEP
pythonpandasstringmethod-chaining
Eisen
Eisen

Reputation: 1897

Assign operator method chaining str.join()

I have the following method chaining code and want to create a new column. but i'm getting an error when doing the following.

(
     pd.pivot(test, index = ['file_path'], columns = 'year', values = 'file')
     .fillna(0)
     .astype(int)
     .reset_index()
     .assign(hierarchy = file_path.str[1:-1].str.join(' > '))
)

Before the assign method the dataframe looks something like this:

file_path       2017  2018  2019  2020
S:\Test\A       0     0     1     2
S:\Test\A\B     1     0     1     3
S:\Test\A\C     3     1     1     0
S:\Test\B\A     1     0     0     1
S:\Test\B\B     1     0     0     1

The error is : name 'file_path' is not defined.

file_path exists in the data frame but I'm not calling it correctly. What is the proper way to create a new column based on another using assign?

Upvotes: 1

Views: 38

Answers (1)

Mustafa Aydın
Mustafa Aydın

Reputation: 18306

you can pass a callable to assign that accepts the dataframe at that point:

.assign(hierarchy=lambda fr: fr["file_path"].str[1:-1].str.join(" > "))

so that fr will be the thus far modified dataframe (pivoted, index resetted etc.), over which you can access to the column "file_path".

Upvotes: 3

Related Questions