In pandas, the melt function is similar:

    In [55]: sample_4_df=flights_sample_df[['year','month','dep_delay', 
    'arr_delay']].head(4)
    In [56]: sample_4_df
    Out[56]: year   month dep_delayarr_delay
    0        2013   3       2       5
    1        2013   1       0       4
    2        2013   11      -7      -27
    3        2013   5       -5      -12
    
    In [59]: pd.melt(sample_4_df,id_vars=['year','month'])
    Out[59]: year   month   variable        value
    0        2013   3       dep_delay       2
    1        2013   1       dep_delay       0
    2        2013   11      dep_delay       -7
    3        2013   5       dep_delay       -5
    4        2013   3       arr_delay       5
    5        2013   1       arr_delay       4
    6        2013   11      arr_delay       -27
    7        2013   5       arr_delay       -12