IndentationError: unindent does not match any outer indentation level

Question

When I compile the Python code below, I get

IndentationError: unindent does not match any outer indentation level

---

Answer 1

IMPORTANT: Spaces are the preferred method - see PEP008 Indentation and Tabs or Spaces?. (Thanks to @Siha for this.)

For Sublime Text users:

Set Sublime Text to use tabs for indentation: View --> Indentation --> Convert Indentation to Tabs

Uncheck the Indent Using Spaces option as well in the same sub-menu above. This will immediately resolve this issue.