93.py

from itertools import combinations, product,permutations
from operator import add, sub, mul, truediv as div

ops = (add,sub,mul,div)

def get_targets(digits,ops,lhs=None):
    if len(digits) == 0:
        return [lhs]
    rhs = digits[0]
    digits = digits[1:]
    if lhs==None:
        return get_targets(digits,ops,rhs)
    op = ops[0]
    ops = ops[1:]
    out = []
    for orhs in get_targets(digits,ops,rhs):
        try:
            out.append(op(lhs,orhs))
        except ZeroDivisionError:
            pass
    if len(ops) > 0:
        try:
            out.extend(get_targets(digits,ops,op(lhs,rhs)))
        except ZeroDivisionError:
            pass
    return out
    

best = 0
best_digits = None
for digits in combinations(range(1,10),4):
    targets = set()
    for digorder in permutations(digits,4):
        for oporder in product(ops,repeat=3):
            targets.update(filter(lambda x: x % 1 == 0 and x > 0, get_targets(digorder,oporder)))
    
    expressible = 0
    while expressible+1 in targets:
        expressible+=1
    if expressible > best:
        best = expressible
        best_digits = digits

print(best, best_digits)