explode list-type cell in pandas

explode.py

# credited to: https://stackoverflow.com/a/40449726

'''
df
              var1  var2 var3
0        [a, b, c]     1   XX
1  [d, e, f, x, y]     2   ZZ
'''

lst_col = 'var1'
pd.DataFrame({
  col:np.repeat(df[col].values, df[lst_col].str.len())
  for col in df.columns.difference([lst_col])
}).assign(**{lst_col:np.concatenate(df[lst_col].values)})[df.columns.tolist()]

'''
var1  var2 var3
0    a     1   XX
1    b     1   XX
2    c     1   XX
3    d     2   ZZ
4    e     2   ZZ
5    f     2   ZZ
6    x     2   ZZ
7    y     2   ZZ
'''