(setq indent-tabs-mode nil)

[ewx]

[Poll #959499]

(Ignoring languages like make where you don't have any choice.)

Comments

[ptc24.livejournal.com]

You missed: prefer spaces to tabs where practical

Or even: prefer spaces to tabs where practical, and always use spaces in Python

so I chose the combination of options that best expressed this.

[sparrowsion]

Agreed.