Python - Is one string column in another?

Question

I have a pandas dataframe with two columns. I need to determine if the string value from one column is in the string value of another column. The second column could be a 'single value' like 'value1' or it could be multiple items separated by a '/' in the string, like this: 'value1/value2/value3'.

For each row, I need to determine if the string is present in the other string in the same row, so that 'value1' in 'value1/value2/value3' would evaluate to True.

My attempts thus far fail to check within each row, and just look to see if the first column string is present in ALL rows column 2.

Here is an example:

import pandas as pd

df = pd.DataFrame({'a':['a','b','c','d','e'],
                   'b':['a/b','c/d','c/a','a/b','e']})

df['a'].isin(df['b'])

Expected result would evaluate to:

True
False
True
False
True

Answer 1

Comprehension

[a in b for a, b in zip(df.a, df.b)]

[True, False, True, False, True]

---

df.assign(In=[a in b for a, b in zip(df.a, df.b)])

   a    b     In
0  a  a/b   True
1  b  c/d  False
2  c  c/a   True
3  d  a/b  False
4  e    e   True

---

Numpy

from numpy.core.defchararray import find

a, b = df.values.astype(str).T
find(b, a) >= 0

array([ True, False,  True, False,  True])

---

df.assign(In=find(b, a) >= 0)

   a    b     In
0  a  a/b   True
1  b  c/d  False
2  c  c/a   True
3  d  a/b  False
4  e    e   True