how to read 2 txt files and write the result in a third file using python : <p>I have 3 files with the following content:</p>

<p>today.txt</p>

<p><strong>570</strong></p>

<p>yesterday.txt</p>

<p><strong>500</strong></p>

<p>now.txt</p>

<p><strong>0</strong></p>

<p>Basically, i need to read the first 2 files and write the result in the third file:</p>

<p>today.txt - yesterday.txt = now.txt (570 - 500 = 70) </p>
