from itertools import permutations
import pandas as pd

Y = {0: 10, 1: 20, 2: 15, 3: 40, 4: 8}
Z = {0: 20, 1: 30, 2: 10, 3: 25, 4: 18}

products = Y.keys()
np = len(products) 
pm = [] # list of permutations
tm = [] # list of makespan time
for order in permutations(products):
    # append permutation to the pm list
    pm.append(order)
    # lookup time for each step
    ty = [0]*(np+1); tz = [0]*(np+1)
    for i in range(np):
        ty[i] = Y[order[i]]
        tz[i+1] = Z[order[i]]
    # calculate makespan time
    t = 0
    for i in range(np+1):
        t += max(ty[i],tz[i])
    tm.append(t)

# convert to Pandas DataFrame for sorting
r = pd.DataFrame(pm,columns=['T0','T1','T2','T3','T4'])
r['makespan'] = tm
r.sort_values('makespan',inplace=True)
print(r.head(10))