Free function that gives a lexicographically bigger string each time : <p>I am implementing a toy db, and I need a <em>free</em> function that gives me a lexicophgraically bigger string each time it's called. It's for naming segment files. </p>

<p>Let's assume I have a max of 1000 files, and I'd prefer if the string was less than 10 characters long.</p>

<p>Could someone give me the easiest example of such a function in python? I'd really like to be a free function as I don't want to introduce complexity with state. </p>
