Random string generator and word search

randomgen.py

import os
import random
import time
from datetime import datetime


def log_to_results(str_to_log):
    fr = open("results.txt", "a")
    fr.write(str_to_log + "\n")
    fr.close()


if os.path.exists("results.txt"):
    os.remove("results.txt")

s = ""
z = ""
while True:
    s = ""
    for j in range(512):
        z = ""
        for i in range(8):
            a = random.randint(0, 1)
            z = z + str(a)
        # print(z)
        x = int(z, 2)
        # print(x)
        if 97 <= x <= 122 or 65 <= x <= 90 or 48 <= x <= 57:
            s = s + chr(x)

    print(s.replace('\r', '').replace('\n', ''))

    mots = ["amour", "infini"]

    for word in mots:
        if word.lower() in s.lower():
            log_to_results(str(datetime.now()) + " " + word)
            print(datetime.now(), word, "FOUND")
            time.sleep(1)