Let's say you want to save many, many files and append these files with a certain sortable index number. As you probably know, you often get in a situation where your files go like this:

    file1
    file101
    file2
    etc.

Which is not ideal when you want your files to go like this:

    file1
    file2
    file101
    etc.

So let's make a function that given the current index number and the maximum index number, it will return a string with leading 0's so that any computer will know how to sort the files. For example, if I were on index 9 and there were a total of 230 files, my function would return '009' so I could append that to my file.