I'm trying to iterate through a list in a PySide2 application. So each time a "Next" button is pressed, the next item is returned from the list and displayed. I could keep track of the index of the entry in my list which was most recently read and manually increment the index on each slot call, but I thought it might be more elegant to turn the slot into a generator function. But it doesn't work.
Minimal (not) working example follows.
import sys
from PySide2.QtWidgets import QApplication, QPushButton
from PySide2.QtCore import SIGNAL, QObject
def func():
stringEntries=["One", "Two", "Three"]
for item in stringEntries:
# In the application this sets the values of a numpy array
# and fires a signal which updates a matplotlib canvas but meh, whatever
print("func ", item, " has been called!")
# This sort of works without the following yield statement
yield
app = QApplication(sys.argv)
button = QPushButton("Next")
QObject.connect(button, SIGNAL ('clicked()'), func)
button.show()
sys.exit(app.exec_())
I was sort of expecting a different string to be printed each time I pressed the "Next" button, but instead it just sits there mocking me...
Is anyone able to point out the thing that I've fundamentally misunderstood please?
As @jasonharper points out in a comment you are creating a new iterator every time the button is pressed that generates the problem, a possible solution is to create a class that has the iterator as an attribute and using the __call__ method that looks over it, to make it simple and elegant I have created a decorator:
from PySide2.QtCore import QObject
from PySide2.QtWidgets import QApplication, QPushButton
class decorator:
def __init__(self, f):
self._f = f
self._iterator = None
def __call__(self, *args, **kwargs):
if self._iterator is None:
self._iterator = self._f(*args, **kwargs)
try:
return next(self._iterator)
except StopIteration:
pass
@decorator
def func():
stringEntries = ["One", "Two", "Three"]
for item in stringEntries:
print("func ", item, " has been called!")
yield
if __name__ == "__main__":
import sys
app = QApplication(sys.argv)
button = QPushButton("Next")
button.clicked.connect(func)
button.show()
sys.exit(app.exec_())