Python-equivalent of short-form "if" in C++

a = '123' if b else '456'

My cryptic version...

a = ['123', '456'][b == True]

While a = 'foo' if True else 'bar' is the more modern way of doing the ternary if statement (python 2.5+), a 1-to-1 equivalent of your version might be:

a = (b == True and "123" or "456" )

... which in python should be shortened to:

a = b is True and "123" or "456"

... or if you simply want to test the truthfulness of b's value in general...

a = b and "123" or "456"

? : can literally be swapped out for and or