change a column value from value found in another column python code example

Example 1: replace one row with another in python

df.loc[(df.Event == 'Dance'),'Event']='Hip-Hop'
df

Example 2: replace value of dataframe with another column

df['col1'] = np.where(df['col1'] == 0, df['col2'], df['col1'])
df['col1'] = np.where(df['col1'] == 0, df['col3'], df['col1'])