CODE EXAMPLE FOR PYTHON

pandas interpolate string

import pandas as pd

s = pd.Series([None, None, 'red', 'red', None, 'blue', None, None])

print(s.to_list())
print(s.bfill().tolist())
print(s.ffill().tolist())
print(s.bfill().ffill().tolist())
print(s.ffill().bfill().tolist())
print(s.interpolate(method='pad').tolist())

Output:
[None, None, 'red', 'red', None, 'blue', None, None]
['red', 'red', 'red', 'red', 'blue', 'blue', None, None]
[None, None, 'red', 'red', 'red', 'blue', 'blue', 'blue']
['red', 'red', 'red', 'red', 'blue', 'blue', 'blue', 'blue']
['red', 'red', 'red', 'red', 'red', 'blue', 'blue', 'blue']
[None, None, 'red', 'red', 'red', 'blue', 'blue', 'blue']