Should I use `app.exec()` or `app.exec_()` in my PyQt application?

Question

I use Python 3 and PyQt5. Here\'s my test PyQt5 program, focus on the last 2 lines:

from PyQt5.QtCore import *
from PyQt5.QtWidgets import *
import sys

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Answer 1

That's because until Python 3, exec was a reserved keyword, so the PyQt devs added underscore to it. From Python 3 onwards, exec is no longer a reserved keyword (because it is a builtin function; same situation as print), so it made sense in PyQt5 to provide a version without an underscore to be consistent with C++ docs, but keep a version with underscore for backwards compatibility. So for PyQt5 with Python 3, the two exec functions are the same. For older PyQt, only exec_() is available.

Answer 2

On the question of whether to prefer one over the other: using exec_ means you have one less thing to worry about if you ever decide to add support for PyQt4 and/or Python >= 2.6, and want to maintain a single code-base.