How to indicate quartile of particular column in pandas dataframe?

Question

I am working on a data frame in python. How can I indicate all the rows that have value for a particular column, 'rate', within specific quartile( ex q1, q2, q3, q4)? Here, interval is range of 'rate', so [-0, 0.913056] is entire range. I want to indicate the value of 'rate' in each row will fall into which quantile of the range.

        name                    rate
0   3POWER ENERGY GROUP INC     -0.000000
1   808 RENEWABLE ENERGY CORP   -0.112192
2   YORK WATER CO                0.774955
3   ZTO EXPRESS (CAYM) INC -ADR  0.086352
4   AEP GENERATING CO            0.850960
5   AEP TEXAS CENTRAL CO         0.600301
6   AIR T INC                    0.254511
7   ALABAMA GAS CORP             0.611631
8   ALABAMA POWER CO             0.913056
9   ALLEGIANT TRAVEL CO          0.227421
10  COMCAST CORP                 0.012037
11  HAWAIIAN ELECTRIC CO         0.670980
12  HAWAIIAN ELECTRIC INDS       0.775778

df like this.

    name                         rate       quartile
0   3POWER ENERGY GROUP INC     -0.000000    q1
1   808 RENEWABLE ENERGY CORP   -0.112192    q1
2   YORK WATER CO                0.774955    q3
3   ZTO EXPRESS (CAYM) INC -ADR  0.086352    q1
4   AEP GENERATING CO            0.850960    q4
5   AEP TEXAS CENTRAL CO         0.600301    q3
6   AIR T INC                    0.254511    q2
7   ALABAMA GAS CORP             0.611631    q3
8   ALABAMA POWER CO             0.913056    q4
9   ALLEGIANT TRAVEL CO          0.227421    q2
10  COMCAST CORP                 0.012037    q1
11  HAWAIIAN ELECTRIC CO         0.670980    q4
12  HAWAIIAN ELECTRIC INDS       0.775778    q4

Answer 1

You need qcut:

df['quartile'] = pd.qcut(df['rate'], 4, ['q1','q2','q3','q4'])
print (df)
                           name      rate quartile
0       3POWER ENERGY GROUP INC -0.000000       q1
1     808 RENEWABLE ENERGY CORP -0.112192       q1
2                 YORK WATER CO  0.774955       q3
3   ZTO EXPRESS (CAYM) INC -ADR  0.086352       q1
4             AEP GENERATING CO  0.850960       q4
5          AEP TEXAS CENTRAL CO  0.600301       q2
6                     AIR T INC  0.254511       q2
7              ALABAMA GAS CORP  0.611631       q3
8              ALABAMA POWER CO  0.913056       q4
9           ALLEGIANT TRAVEL CO  0.227421       q2
10                 COMCAST CORP  0.012037       q1
11         HAWAIIAN ELECTRIC CO  0.670980       q3
12       HAWAIIAN ELECTRIC INDS  0.775778       q4