Conditions

if, elif, else and what counts as true.

Branching

if runs a block when a condition holds, elif tests the next possibility, and else catches the rest. Comparisons chain naturally, so 0 < x < 10 reads as it looks.

and, or and not are words rather than symbols.
Use is only for None and other singletons, not for comparing values.

Truthiness

Empty things are false: 0, "", [], {}, set() and None. Everything else is true, so if items: is the idiomatic way to ask whether a list has anything in it.