Always remember
If you ever have to name variables suffixed by numbers as in your example, you should consider a sequential indexable data structure like array or list. In Python to create a List we do
var = [[mass_a, velocity_a, velocity_a],
[mass_b, velocity_b, velocity_b]]
If you ever have to name variables with varying suffixes like
var_A=[mass_a, velocity_a, velocity_a]
var_B=[mass_b, velocity_b, velocity_b]
you should consider a non-sequential indexable data structure like hashmap or dictionary. The key of this dictionary should be the varying suffix and the values should be the values assigned to the respective variable In Python to create a dictionary we do
var = {'A':[mass_a, velocity_a, velocity_a],
'B':[mass_b, velocity_b, velocity_b]}