title: python itertools dont load files into memory
body: <p>I have some what big files and I'm trying to get all combinations with this code</p>
  <pre><code>for text1, text2 in itertools.product(open('text1.txt'), open('text2.txt')):
      t3 = (text1.strip() + text2.strip())
      time.sleep(1)
      print(t3)
  
  </code></pre>
  <p>testing with small files it worked fine but when using big files nothing happens I'm guessing its loading the file into memory anyway so it doesn't load the whole file into memory</p>