lucky.py

import ctypes
import os
import subprocess
import tempfile

__code__ = """
#include <stdbool.h>

bool check(unsigned long long int n) {
    int sum = 0;
    while (n > 0) {
        sum += n % 10;
        n /= 10;
    }
    return sum % 7 == 0;
}
"""

path = tempfile.mkdtemp()
cfile = os.path.join(path, "lib.c")
sofile = os.path.join(path, "lib.so")

open(cfile, "w").write(__code__)
__cmd__ = "gcc -O3 -shared -o %s %s" % (sofile, cfile)
if os.environ.get("DEBUG"):
    print(__cmd__)
subprocess.run(__cmd__.split(" "))

lib = ctypes.CDLL(sofile)

lib.check.restype = ctypes.c_bool
lib.check.argtypes = [ctypes.c_ulonglong]

check = lib.check

if __name__ == "__main__":
    print(check(14))  # False
    print(check(16))  # True
    print(check(123))  # False
    print(check(777))  # True
    print(check(9999999))  # True