python操作列表加减 一个列表减去另外一个列表

 # list subtract
    role_dongyu.permissions = list(set(role_dongyu.permissions) - set(all_permission))

    # list add
    role_dongyu.permissions = role_dongyu.permissions + all_permission
    role_dongyu.permissions = list(set(role_dongyu.permissions))

def set_approach(a,b):
    return list(set(a)-set(b))

参考
https://stackoverflow.com/questions/2514961/remove-all-values-within-one-list-from-another-list