If you think it should be acceptable to mix tabs and spaces in a source file, then one of the attractive features Python offers its users is the assurance that they'll never find themselves working on a project with you.
Spoken like a true believer. Did you know some editors offer the use of tabs for indent and spaces for alignment? The chances for a space to get into the left hand indent side are pretty high in such a system, which I imagine is dealt with harshly in your world. I am happy to self-select myself out of it.