Add specific constraint on schedule

[gelazari]

I have the problem of 2 shops, the requirements per day per shop, N drivers and 7 days of week. My constraints are 1) a driver cannot work more than 6 days, i.e. 1 day-off ii) day requirement of drivers per shop must be satisfied and iii) a driver that has been allocated to work for shop 1 on day 1 cannot be allocated to work for shop 2 on day 2. I think that I have tackled constraints i and ii but I can't find a way to implement solution iii. Here's my code. Any help would be highly appreciated.

import numpy as np
import pulp
import pandas as pd

day_requirement = [[2, 5, 4, 2, 5, 3, 4], [5, 4, 2, 5, 3, 4, 2]]

# N = max(day_requirement)  # The number of drivers
N = 15
D = 7  # The number of days in week
H = 2

var = pulp.LpVariable.dicts('VAR', (range(H), range(N), range(D)), 0, 1, 'Binary')

problem = pulp.LpProblem('shift', pulp.LpMinimize)

obj = None
for h in range(H):
    for i in range(N):
        obj += pulp.lpSum(var[h][i][j] for j in range(D))
problem += obj

# schedule must satisfy daily requirements
for j in range(D):
    for h in range(H):
        c = None
        for i in range(N):
            c += var[h][i][j]
        problem += c == day_requirement[h][j]

# cannot work more than 6 days
for d in range(N):
    for h in range(H):
        problem += pulp.lpSum([var[h][d][j] for j in range(D)]) <= 6

print(problem)

# Solve problem.
status = problem.solve()