check for dictionary keys

[faulkner]

def all(s):
    for x in s:
        if not x: return False
    return True


bad_combos = [['-A', '-B'], ['-A', '-C'], ...]
for bad_combo in bad_combos:
    assert not all([bad_elem in a for bad_elem in bad_combo])

micklee74 at hotmail.com wrote:
> hi
> in my code, i use dict(a) to make to "a" into a dictionary , "a" comes
> from user input, so my program does not know in the first place. Then
> say , it becomes
>
> a = { '-A' : 'value1' , '-B' : "value2" , "-C" : "value3" , '-D' :
> 'value4' }
>
> somewhere next in my code, i will check for these..:
>
> 1)  -A and -B cannot exist together
> 2) -A and -C cannot exist together
> 3) -A and -B and -D cannot exist together
> 4) and lots of other combinations to check for....
>
> how can i efficiently check for the above? At first as i do simple
> checks , i use if and else.
> But as i began to check for more combinatoiuns, it gets messy....
> 
> thanks.