Sort data frame in ascending order by mean of other column

Question

I have a data frame:

df = 

ID  Num
a   3
b   4
b   2
a   1

Want to sort in ascending order by taking into account unique values of ID column

---

My Try:

df.sort_values(by=['Num'])

But it gave me ascending order by neglecting ID column

---

Desired output:

df = 

ID  Num
a   1
a   3
b   2
b   4

Answer 1

Just do:

df.sort_values(['ID', 'Num'])

Output

  ID  Num
3  a    1
0  a    3
2  b    2
1  b    4