Conditionally entering a for loop

Question

What is a way to avoid code repetition to loop if argument is a sequence (list, tuple) or to skip the loop but execute the action just once?

def foo(arg1,sequence=None):
    # If possible, loop, else do it once
        if isinstance(sequence,(list,tuple)):
            for value in sequence:
                do_something(arg1)
        else:
            do_something(arg1)

The actions I do in the for loop are way longer than this, and I was wondering what approach you normally use to avoid this, if you do avoid it. I often come across this issue and I haven't come up with something to 'solve' it.

EDIT: Question is not a duplicate of In Python, how do I determine if an object is iterable?, as suggested. I do not want to introduce a different condition. I want to avoid the repetition.

Answer 1

Standardise on the loop being the default case and transform your single case into an iterable:

if not isinstance(sequence, (list, tuple)):
    sequence = [sequence]

for value in sequence:
    do_something(value)