Replace dataframe column with split columns

Question

How can I replace dataframe column with columns after it split? I know how to split column but don't know how to replace it with split value columns.

Input:

import pandas as pd

df = pd.DataFrame({'id': [101, 102],
                   'full_name': ['John Brown', 'Bob Smith'],
                   'birth_year': [1960, 1970]})
df_new = df['full_name'].str.split(" ", expand=True)
print(df)
print(df_new)

Output:

    id   full_name  birth_year
0  101  John Brown        1960
1  102   Bob Smith        1970
      0      1
0  John  Brown
1   Bob  Smith

Expected Output:

    id first_name last_name  birth_year
0  101       John     Brown        1960
1  102        Bob     Smith        1970

Answer 1

df.join(df.full_name.str.split('\s', expand = True) \
                                    .set_axis(['first_name', 'last_name'], axis = 1)) \
                                                [['id', 'first_name', 'last_name', 'birth_year']]

Output:

    id   full_name  birth_year
0  101  John Brown        1960
1  102   Bob Smith        1970

Answer 2

Strategy is to get the position of the column you wish to replace, create the new columns, and concatenate the new and old dataframes with respect to the position of the column u wish to replace:

#get the position of the column to be replaced
col_position = df.columns.get_loc('full_name')

#create new dataframe that holds the new columns
insert_df = (df
            .pop('full_name')
            .str.split(expand=True)
            .set_axis(['first_name','last_name'],axis='columns')
            )

df_by_positions = (#this is the dataframe before col_position
                   [df.iloc[:,:col_position],
                   #this is the dataframe we are inserting
                   insert_df,
                  #this is the dataframe after col_position
                  df.iloc[:,col_position:]
                  ]
                  )

pd.concat(df_by_positions,axis=1)

     id first_name  last_name   birth_year
0   101   John       Brown       1960
1   102   Bob        Smith       1970