Multiple conditionals in lambda function in pandas dataframe

Question

I am trying to create a new column in my pandas Dataframe by passing multiple conditional statements through a lambda function.

My question is very similar to this one: Lambda including if...elif...else but the solution doesn't seem to work for my version of python (3.7).

Here's what I have so far:

With one condition, this works:

ops['repair_location'] = ops['depot_name'].apply(lambda x: 'Field' if x == 'Field else 'Depot')

But I want to add another condition. Using the solution to the linked question:

ops['repair_location'] = ops['depot_name'].apply(lambda x: 'Field' if x == 'Field' else (x == 'Unknown Location' 'Unknown Location' else 'Depot'))

This returns a syntax error pointing to the last else statement.

What were you intending with this expression: x == 'Unknown Location' 'Unknown Location'? In any case, you just have a bare-except, that isn't a complete conditional expression. You really should just use a full function definition, this lambda will quickly become unreadable — juanpa.arrivillaga
– juanpa.arrivillaga, Commented Apr 16, 2020 at 0:26

Allen Qin · Accepted Answer · 2020-04-16 00:26:31Z

2

You can use np.where

import numpy as np
ops['repair_location'] = (
    ops['depot_name']
    .apply(lambda x: np.where(x=='Field', 'Field', np.where(x=='Unknown Location', 'Unknown Location', 'Depot')))
)

answered Apr 16, 2020 at 0:26

Allen Qin

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2 Comments

BENY Over a year ago

May I know why we do apply here?

Allen Qin Over a year ago

That's what the OP wanted to use and just trying to make it work.

BENY · Accepted Answer · 2020-04-16 00:32:43Z

2

We usually do np.select

s1=ops['depot_name']=='Field'
s2=ops['depot_name']=='Unknown Location'
ops['repair_location']=np.select([s1,s2],['Field','Unknown Location'],default='Depot')

edited Apr 16, 2020 at 0:32

answered Apr 16, 2020 at 0:24

BENY

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2 Comments

Jacky Over a year ago

The column depot_name has values outside of 'Field' and 'Unknown Location'. This rewrites it and returns an error ValueError: invalid entry 0 in condlist: should be boolean ndarray

BENY Over a year ago

@Jacky please try again typo '=='

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