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

i use python 3 , pyqt5. here's test pyqt5 program, focus on last 2 lines:

from pyqt5.qtcore import * pyqt5.qtwidgets import * import sys  class window(qwidget): def __init__(self,parent=none):     super().__init__(parent)     self.setwindowtitle('test')     self.resize(250,200)  app=qapplication(sys.argv) w=window() w.show() sys.exit(app.exec()) #sys.exit(app.exec_()) 

i know exec language keyword in python. code on official pyqt5 documentation (specifically object destruction on exit part). see example shows use of app.exec() confuses me.

when tested on machine. found there no visible difference end. both , without _ produces same output in no time difference.

my question is:

• is there wrong going when use app.exec()? clashing python's internal exec? suspect because both exec's executing something.
• if not, can use both interchangeably?

that's because until python 3, exec was reserved keyword, pyqt devs added underscore it. python 3 onwards, exec no longer reserved keyword (because builtin function; same situation print), made sense in pyqt5 provide version without underscore consistent c++ docs, keep version underscore backwards compatibility. pyqt5 python 3, 2 exec functions same. older pyqt, exec_() available.