Cython

def primes(int kmax):  # L'argument sera converti en nombre ou provoquera un TypeError.
    cdef int n, k, i  # Ces variables sont déclarées avec des types en C.
    cdef int p[1000]  # un autre typage C
    result = []  # un typage Python
    if kmax > 1000:
        kmax = 1000
    k = 0
    n = 2
    while k < kmax:
        i = 0
        while i < k and n % p[i] != 0:
            i = i + 1
        if i == k:
            p[k] = n
            k = k + 1
            result.append(n)
        n = n + 1
    return result

In [1]: %load_ext Cython

In [2]: %%cython
   ...: def f(n):
   ...:     a = 0
   ...:     for i in range(n):
   ...:         a += i
   ...:     return a
   ...: 
   ...: cpdef g(int n):
   ...:     cdef long a = 0
   ...:     cdef int i
   ...:     for i in range(n):
   ...:         a += i
   ...:     return a
   ...: 

In [3]: %timeit f(1000000)
10 loops, best of 3: 26.5 ms per loop

In [4]: %timeit g(1000000)
1000 loops, best of 3: 279 µs per loop