Execute loop only once if condition is met

Question

I was wondering if there is a pythonic way to write a code equivalent to the one below without defining doSomething as a separate function.

if test:
    for i in s:
        doSomething()
else:
    doSomething()

In particular, I am thinking of the use case where test checks if s exists.

Any suggestions?

Answer 1

You could possibly do this:

for i in (s if test else [False]):
    doSomething()

Answer 2

You want to execute dosomething once if s exists, otherwise len(s) times.

for i in s if test else [0]:
    dosomething()

The iteratable is a ternary expression:

s if test else [0]

The else value can be any sequence of a single element; since you don't actually use the i value for dosomething , it could also be more clear:

limit = len(s) if test else 1
for i in range(limit):
    dosomething()