#Решение прошло import pandas as pd logs = pd.read_csv('/datasets/logs.csv') logs['email'] = logs['email'].fillna(value='') logs.loc[logs['source'] == 'None', 'source'] = 'email' print(logs['source'].value_counts()) other 133834 context 52032 email 13953 undef 181 Name: source, dtype: int64 #Решение не прошло import pandas as pd logs = pd.read_csv('/datasets/logs.csv') logs['email'] = logs['email'].fillna(value='') logs['source'].loc[logs['source'] == 'None'] = 'email' print(logs['source'].value_counts()) See the caveats in the documentation: https://pandas.pydata.org/pandas-docs/stable/user_guide/indexing.html#returning-a-view-versus-a-copy self._setitem_single_block(indexer, value, name) other 133834 context 52032 email 13953 undef 181 Name: source, dtype: int64