Extract part of the string in python using apply and lambda

There are certain situations where we have to extract certain portions from text fields/columns. We can do this using a combination of apply,lambda and split functions.For our blog, we will use a LOT( line of therapy) example where a gien cell has compressed values of therapy progression and we are trying to extract the first line of therapy¶

Step 1: Importing Libraries¶

In [3]:

import pandas as pd
import numpy as np
import re

In [4]:

# Lets look at a small example
# Here each line of treatment is separated by |
# So LOT1 is the first line of therpay
# LOT2 is the first line of therpay
txt = 'LOT 1 | LOT2'
txt.split("|")

Out[4]:

['LOT 1 ', ' LOT2']

In [13]:

# We see that we can use split function to break the text
# And then use positional arguemnts to extract the required lOT

Step 2: Creating the sample dataset¶

In [5]:

Line_of_Therapy = ['Drug 1 | Drug 2','Drug 1 + Drug 3 | Drug 4 + Drug 5 | Drug 3']
Line_of_Therapy

Out[5]:

['Drug 1 | Drug 2', 'Drug 1 + Drug 3 | Drug 4 + Drug 5 | Drug 3']

In [6]:

Patient = [1,2]
Patient

Out[6]:

[1, 2]

In [7]:

df = pd.DataFrame(np.array([Patient,Line_of_Therapy])).T
df.columns=['Patient','Line of Therapy']
df

Out[7]:

	Patient	Line of Therapy
0	1	Drug 1 | Drug 2
1	2	Drug 1 + Drug 3 | Drug 4 + Drug 5 | Drug 3

Step 3: Extracting the second Line of therapy¶

Using apply and lambda to extract the required component¶

In [8]:

df['LOT2']=df['Line of Therapy'].apply(lambda x: x.split("|")[1].strip())
df

Out[8]:

	Patient	Line of Therapy	LOT2
0	1	Drug 1 | Drug 2	Drug 2
1	2	Drug 1 + Drug 3 | Drug 4 + Drug 5 | Drug 3	Drug 4 + Drug 5

We can see that using apply and lambda, we were able to extract the second LOT¶