Paul, your comments are interesting, but your proposed patch doesn't actually solve the problem.

So here I am typing away at my command prompt, and I type in a couple optional parameters I know I'll need and start on the sequence of positional ones, and half way through I remember "oh, I need another optional paremeter" so I type it in next before I forget, and then go on with the positional ones.

No prior Unix-style argument parsing mechanism that I have ever seen or heard of would be confused by that, but argparse is.

This bug is about providing a facility in argparse that supports intermixing optional parameters into strings of positional parameters, just like all prior Unix-style argument parsing mechanisms, so that an application can be ported to use argparse without breaking command lines that their users have stored in command files. Otherwise argparse is not an upgrade path for an application, yet optparse has been deprecated.