Try to avoid extraneous spaces in lists and tuples. Python programs should be relatively compact. Prose writing typically keeps ()'s close to their contents, and puts spaces after commas, never before them. This should hold true for Python, also. The preferred formatting for lists and tuples, then, is (1,2,3) or (1, 2, 3). Spaces are not put after the enclosing [ ]'s or ( )'s. Spaces are not put before ,'s.