For a given range for n variables. I have taken n=3 as an example.
A : [1,3]
B: [5,10,12]
C: [100,113]
Note the values in the above range
Using Itertools.product I can make all combinations of a list, afterwards you can write each combination to your DataFrame
import itertools
A = [1, 3]
B = [5, 10, 12]
C = [100, 113]
a = [A, B, C]
print(list(itertools.product(*a)))
# Outputs [(1, 5, 100), (1, 5, 113), (1, 10, 100), (1, 10, 113), (1, 12, 100), (1, 12, 113), (3, 5, 100), (3, 5, 113), (3, 10, 100), (3, 10, 113), (3, 12, 100), (3, 12, 113)]
idx = ['c{}'.format(i) for i in range(1, len(data)+1)]
data = list(itertools.product(*a))
df = pd.DataFrame(data, index=idx, columns=list('abc')).T
df
c1 c2 c3 c4 c5 c6 c7 c8 c9 c10 c11 c12
a 1 1 1 1 1 1 3 3 3 3 3 3
b 5 5 10 10 12 12 5 5 10 10 12 12
c 100 113 100 113 100 113 100 113 100 113 100 113