1. Use and-or in old versions

bool and a or b

Note that a must be "true", i.e.,

for numbers: 0 - "false", others - "true"

for strings: "" - "false", others - "true"

for lists: [] - "false", others - "true"

for tuples: (,) - "false", others - "true"

for dictionaries: {} - "false", others - "true"

otherwise, one may confront weired behaviors.

For example,

(k>1) and row[k] or "."

would come to row[k] if k is greater than one, a dot otherwise.

But be careful, if row[k] is an empty string, the result will be ".", because (k>1) and False comes out False, always!

2. Improved and-or

Dive Into Python mentioned an improved and-or expression

(bool and [a] or [b])[0]

Since [a] is "true" whatever a is (even [[]] is "true"?), the and-or trick always works as expected.

3. Boolean index

Consider this

[a, b][int(not bool)]

if bool == True, not bool becomes False, int(False) returns 0, which indexes a. I have never tested this...

4. Higher versions provide a if bool else b

a if bool else b

It's the well-known story now. Although the sequence of a, bool and b seems a little strange ^_^