How to change pandas col that is a list of values to float or int values

Question

I have a dataframe col called a which is a list of values.

a           |  b        
[-1,0,1,2,3]| "test"

How do I change this col a to be like

a | b    
-1| "test"
0 | "test"
1 | "test"
2 | "test"
3 | "test"

I have been trying to explode the values

df = df.assign(a = df.a.str.split(',')).explode('a')