if len(lst) == N == len( set(lst) ):
    print( "Да" )

def f(num,lst): return reduce(lambda x,y:x+y,map(lambda x: num==x,lst))

def g(numlst,lst):                                                     
    for num in numlst:
        if f(num,lst) != 1:
            return False
    return True

In [44]: l
Out[44]: [1, 3, 9, 0, 5, 1, 8, 3, 4, 10, 100500, 100500]

In [45]: set(l)
Out[45]: set([0, 1, 3, 4, 5, 8, 9, 10, 100500])

In [46]: g([1,2,3],l)
Out[46]: False

In [47]: g([1,2,3],set(l))
Out[47]: False

In [48]: g([0,1,3],l)
Out[48]: False

In [49]: g([0,1,3],set(l))
Out[49]: True

a=numpy.zeros(N)
a[arr]=1
if min(a)==0:
     print "не хватает"

if 6*sum( i*i for i in lst ) == N*(N+1)*(2*N+1):
    print( "Да, это так" )