PyQt stacked widget not moving to next page until function ends - widget

Question

Hi i have a program that when a button is pressed it should move to the next stacked widget replace some text in some labels and then execute some functions but this is not working and moves to the next page when the functions completes
The code is :
QtCore.QObject.connect(self.StartBtn, QtCore.SIGNAL(_fromUtf8("clicked()")), self.start) #Start
def nextPage(self):
current_page = self.stackedWidget.currentIndex()
i = int(current_page) + 1
self.stackedWidget.setCurrentIndex(i)
def start(self):
self.nextPage()
self.animation()
self.runFunctions()
def runFunctions(self):
try:
self.DbLabel.setText(_translate("MainWindow", "Checking Database", None))
if checkDb == True:
self.DbLabel.setText(_translate("MainWindow", "Checking Database ", None))
self.checkDbFun()
self.DbLabel.setText(_translate("MainWindow", "Database checked", None))
else:
self.checkedDbImg.setPixmap(QtGui.QPixmap(_fromUtf8("Files\\x.png")))
self.DbLabel.setText(_translate("MainWindow", "Database not checked", None))
except Exception as e:
self.AlertMessage(e)
def animation(self):
self.LoadingGif = QtGui.QLabel(MainWindow)
movie = QtGui.QMovie("Files\\loading.png")
self.LoadingGif.setMovie(movie)
self.LoadingGif.setAlignment(QtCore.Qt.AlignCenter)
self.gridLayout_2.addWidget(self.LoadingGif, 4, 1, 1, 1)
movie.start()
So what i want is to press StartBtn then move to next stacked widget page load the animation image and then run the functions

Answer 1

You probably need to let Qt process events in order for the tab change to take effect. You could do that two ways:
insert a qApp.processEvents() between the animation() and runFunctions() (qApp is in PyQt5.QtWidgets)
call runFunctions() via a single-shot timer: QTimer.singleShot(0, runFunctions), which will schuedule runFunctions via the event loop, so any pending events will first be processed (because runFunctions() is the latest added), then runFunctions() will get called. If you actually have params for runFunctions(), use a lambda.
I favor the first approach because I find it more clearly indicates what is happening (events need to be processed), but I recommend also adding a comment on that line that "so stack tab can change".
BTW you should be use the new-style notation for signals-slot connections, much cleaner, of the form "signal.connect(slot)":
self.StartBtn.clicked.connect(self.start)
So for approach #1 your code would look like this:
from PyQt5.QtWidgets import qApp
...
self.StartBtn.clicked.connect(self.start)
...
def start(self):
self.nextPage()
self.animation()
qApp.processEvents()
self.runFunctions()
...