Comment by zo1

You can't always rely on for-loop mechanics to do branching.

Also, having an implied "conditional" that must be extracted by reading the head-portion of a loop is very very unreadable. I'd reject your submission on a code-review.

Instead, you should do something like below. I assume that your example is contrived, so for the sake of argument, assume I have all sorts of business cruft around mine. I.e. should_process exists because there are business rules for processing/not processing the master_list.

    def should_process(master_list):
        return master_list is not None and len(master_list) > 0

    def main_doing_of_stuff_foo():
        if not should_process(masterList):
            return  # Yes, this thing should be in its own method so you can do an early exit.

        for item in masterList:  # Yes, you should be using an iterator as well, not indexing.
            print("Body goes here".)