how do I use .assign for values in a column-CodePudding

I have a dataframe which looks like this:

        date        symbol      numerator   denominator
4522    2021-10-06  PAG.SG      1.0         18
1016    2020-11-23  IPA.V       1.0         5
412     2020-04-17  LRK.AX      1.0         30
1884    2021-06-03  BOUVETO.ST  1.0         1
2504    2021-04-28  VKGYO.IS    1.0         100
3523    2021-07-08  603355.SS   1.0         1
3195    2021-08-23  IDAI        1.0         1
3238    2021-08-19  6690.TWO    1.0         1000
3430    2021-07-19  CAXPD       1.0         10
2642    2021-04-15  035720.KS   1.0         1

dtypes: date: object symbol: object numerator: float64 denominator: int64

I am trying to use pd.assign to assign a classifier to this df in the form of

df = df.assign(category = ['forward' if numerator > denominator else 'reverse' for numerator in df[['numerator', 'denominator']]])

But I'm receiving a TypeError stating: TypeError: Invalid comparison between dtype=int64 and str

I have tried casting them explicitly, with:

df = df.assign(category = ['forward' if df['numerator'] > df['denominator'] else 'reverse' for df['numerator'] in df])

But receive another TypeError stating: TypeError: '>' not supported between instances of 'str' and 'int'

Which is confusing because I'm not comparing strings, I'm comparing int and float.

Any help would be greatly appreciated.

CodePudding user response：

You still can do that with np.where

import numpy as np 
df = df.assign(category = np.where(df['numerator']>df['denominator'],
                                   'forward',
                                   'reverse')