In Python, how do I change one column of a dataframe based on another?

Question

In a dataframe with columns x and y , how would I write code so that if a row has an x string but a 'Not assigned' y string (the y column contains the string "Not assigned"), then the y string will be the same as the x string?
(Overwriting the "Not assigned" string in column y with the contents of column x )

Answer 1

You can use df.iterrows() checking the values of the columns conditionally as you iterate.

import pandas as pd

df = pd.DataFrame(data={'x': [1,2,3], 'y': [6, "Not Assigned", 8]})

for index, value in df.iterrows():
  if value['y'] == 'Not Assigned':
    df['y'][index] = df['x'][index]

Output:

    x   y
0   1   6
1   2   2
2   3   8

Answer 2

df.loc[df['y']=='Not assigned', 'y'] = df.loc[df['y']=='Not assigned', 'x']

would do it