cas

CACHE = {}


def set(key, value):
    CACHE[key] = value
    return True


def get(key):
    return CACHE.get(key)


def delete(key):
    if key in CACHE:
        del CACHE[key]


def flush():
    CACHE.clear()


def gets(key):
   v = CACHE.get(key)
   if v:
        return v, hash(repr(v))

def cas(key, value, cas_unique):
   r = gets(key)
   if r:
        val, unique = r
        if unique == cas_unique:
            return set(key, value)
        else:
            return False
    
print set('x', 1)

print get('x')

print get('y')

delete('x')
print get('x')

set('x', 2)
print gets('x')
print cas('x', 3, 0)

print cas('x', 5, 6400019251)

print get('x')