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How to align center while having an expanding size policy?

I am following a bunch of guides I managed to come close to what I expect for my program to look. However with the solution I came to the button is added at the top-left corner of the main layout (layout_main), while I'd like it to be centered. This is my code:
import sys
from PyQt5.QtCore import Qt
from PyQt5.QtWidgets import (
QApplication,
QLabel,
QMainWindow,
QPushButton,
QSizePolicy,
QTabWidget,
QVBoxLayout,
QWidget,
qApp,
)
class MainWindow(QMainWindow):
def __init__(self):
super().__init__()
self.setWindowTitle("Test")
self.setGeometry(0, 0, 1000, 700)
btn_start = QPushButton("Test button", self)
btn_start.setSizePolicy(QSizePolicy.Expanding, QSizePolicy.Expanding)
btn_start.setMaximumSize(900, 500)
btn_start.setMinimumSize(200, 200)
lbl_test = QLabel("Test label", self)
layout_main = QVBoxLayout()
layout_main.addWidget(btn_start)
#layout_main.setAlignment(btn_start, Qt.AlignCenter)
layout_main.addWidget(lbl_test)
tabs = QTabWidget(self)
tabs.setTabPosition(QTabWidget.North)
tabs.setMovable(True)
main = QWidget(self)
main.setLayout(layout_main)
tabs.addTab(main, "Main tab")
self.setCentralWidget(tabs)
app = QApplication(sys.argv)
window = MainWindow()
window.show()
sys.exit(app.exec_())
And this is how it looks
When I tried to center it with layout_main.setAlignment(btn_start, Qt.AlignCenter), the commented line, then the button is centered, but sized down to the minimum size
How can I center the button while having it expand the way I want? I have tried lots of things like adding the button to it's own layout or inside a container widget, but no solution worked yet.

I run your code and find out that the btn_start.setMaximumSize limit the button to expand.
Edit your code as I told you now, if there are other problems comment and I will edit the solution.

Pyqt5 make QSplitter handle colorful/distinguishable

I want to change the way my splitter handle looks in Pyqt5. In the code below, consider self.widg_1 and self.widg_2 to be any two widgets. Using setStyleSheet results in the error:
self.my_splitter_handle.setStyleSheet("border: 3px blue")
AttributeError: 'NoneType' object has no attribute 'setStyleSheet'
import sys
from PyQt5.QtCore import Qt
from PyQt5 import QtGui
from PyQt5.QtWidgets import QApplication, QWidget, QFrame, QLineEdit, QHBoxLayout, QSplitter
class MyMainWindow(QWidget):
def __init__(self):
super().__init__()
self.title = "PyQt5 Splitter"
self.top = 200
self.left = 500
self.width = 400
self.height = 300
hbox = QHBoxLayout()
self.widg_1 = QFrame()
self.widg_1.setFrameShape(QFrame.StyledPanel)
self.my_splitter = QSplitter(Qt.Horizontal)
self.widg_2 = QLineEdit()
self.my_splitter.addWidget(self.widg_1)
self.my_splitter.addWidget(self.widg_2)
self.my_splitter.setSizes([200, 200])
hbox.addWidget(self.my_splitter)
# Note: splitter handle 0 is always hidden and handle 1 is between the widgets 1 & 2
self.my_splitter_handle = self.my_splitter.handle(1)
self.my_splitter_handle.setStyleSheet("background: 3px blue;")
self.setLayout(hbox)
self.setWindowTitle(self.title)
self.setGeometry(self.left, self.top, self.width, self.height)
self.show()
App = QApplication(sys.argv)
window = MyMainWindow()
sys.exit(App.exec())
Note: I just want a decent and prominent looking splitter handle with an arrow or some other marker like the one in the image.

QPlainTextEdit is RightToLeft but displays LeftToRight

I made a view with QPlainTextEdit and set setLayoutDirection(QtCore.Qt.RightToLeft). The output of self.plaintxt.isRightToLeft()is 1 but in the plain text view, persian and english text are displayed from left. What is happen in my code?
Code:
import sys, re
from PyQt5 import QtCore
from PyQt5.QtWidgets import QApplication, QLabel, QLineEdit, QMainWindow, QPushButton, QFileSystemModel, QTreeView, \
QFileDialog, QComboBox, QPlainTextEdit
from PyQt5.QtCore import pyqtSlot
class App(QMainWindow):
def __init__(self):
super(App, self).__init__()
self.title = 'by PyQt5 and python 3.7'
self.left = 10
self.top = 10
self.width = 1000
self.height = 500
self.initUI()
def initUI(self):
self.setWindowTitle(self.title)
self.setGeometry(self.left, self.top, self.width, self.height)
self.btn_browse = QPushButton('Browse', self)
self.btn_browse.move(50, 20)
self.btn_browse.clicked.connect(self.on_click)
self.textbox = QLineEdit(self)
self.textbox.move(170, 20)
self.textbox.resize(280, 40)
self.textbox.setAlignment(QtCore.Qt.AlignRight) # It is in right.
self.page_view = QPlainTextEdit(self)
self.page_view.move(20, 100)
self.page_view.resize(800, 400)
self.page_view.setLayoutDirection(QtCore.Qt.RightToLeft) # It is not in right.
self.show()
if __name__ == '__main__':
app = QApplication(sys.argv)
ex = App()
sys.exit(app.exec_())

QWidget.setLayoutDirection no longer affects the text layout direction (Qt.LeftToRight or Qt.RightToLeft) of QTextEdit, QLineEdit and widgets based on them.
To programmatically force the text direction , you can change the defaultTextOption of the QTextDocument associated with that widget with a new QTextOption of different textDirection property.
QTextDocument *QPlainTextEdit::document() const
Returns a pointer to
the underlying document.
void QTextDocument::setDefaultTextOption(const QTextOption &option)
Sets the default text option to option.
self.page_view.document().setDefaultTextOption(QTextOption(Qt.AlignRight))

Don't use QPlainText, as it uses internally QPlainTextDocumentLayout which does not fully support RTL (automatic alignment for example - like you are looking for). You can use QTextEdit, or use a different document layout class (like QTextDocumentLayout) in your QPlainText.
The reason for those Plain classes exist, is to be faster by removing features... which you need.

Dynamic positioning of widgets in PyQt5?

I want my window to have this layout:
The graph will be from matplotlib.
I want a way of dynamically creating this layout, so that it would fit to any sized screen without changing the basic layout. How do I do this? This is what I've got so far:
import sys
from PyQt5.QtWidgets import (QWidget, QPushButton,
QHBoxLayout, QVBoxLayout, QApplication, QFrame, QScrollArea, QListWidget, QListWidgetItem, QLabel)
class Example(QWidget):
def __init__(self):
super().__init__()
self.initUI()
def initUI(self):
#top left downwards
vbox = QVBoxLayout()
vbox.addStretch(1)
hbox = QHBoxLayout()
hbox.addStretch(1)
hbox.addLayout(vbox)
hbox.setDirection(1)
self.setLayout(hbox)
qlist = QListWidget()
hbox.addWidget(qlist)
for i in range(0,31):
qlist.addItem(str(i))
qlist.setFrameStyle(QFrame.Raised)
vbox2 = QVBoxLayout()
vbox2.addStretch()
graph = QFrame(self)
graph.setStyleSheet("QWidget { background-color: red }" )
vbox2.addWidget(graph)
graph.setFrameShape(1)
self.setStyleSheet("font: 20pt Cambria")
self.showMaximized()
self.show()
if __name__ == '__main__':
app = QApplication(sys.argv)
ex = Example()
sys.exit(app.exec_())
Which gives me this:
Anyone know how to do this? I'm new to PyQt5 and am not sure how box layouts work after looking at multiple examples. Is there an easier way of doing this without the layout being disturbed?
Thanks!

The first thing you have to do is design your project, for example in your case you have two elements placed vertically: the red QFrame and something underneath, that something underneath commands an element handling the horizontal position so that below it must be a QHBoxLayout, and the element which places the QFrame and is something below it must be a QVBoxLayout, that is your simple structure that you could express it using the following scheme
QWidget
└── QVBoxLayout
├── QFrame
└── QHBoxLayout
└── QListWidget (with stretch = 1)
I prefer to create the widgets first and finally add it to the respective layouts.
import sys
from PyQt5 import QtWidgets
class Example(QtWidgets.QWidget):
def __init__(self):
super().__init__()
self.initUI()
def initUI(self):
# create widgets
graph = QtWidgets.QFrame()
graph.setFixedHeight(40)
graph.setFrameShape(QtWidgets.QFrame.Box)
graph.setStyleSheet("QWidget { background-color: red }" )
qlist = QtWidgets.QListWidget()
qlist.setFrameStyle(QtWidgets.QFrame.Raised)
qlist.addItems(map(str, range(31)))
# create QHBoxLayout and add QListWidget
hlay = QtWidgets.QHBoxLayout()
hlay.addWidget(qlist)
hlay.addStretch(1)
# create QVBoxLayout and add QFrame and QHBoxLayout
vlay = QtWidgets.QVBoxLayout(self)
vlay.addWidget(graph)
vlay.addLayout(hlay)
self.setStyleSheet("font: 20pt Cambria")
self.showMaximized()
if __name__ == '__main__':
app = QtWidgets.QApplication(sys.argv)
ex = Example()
sys.exit(app.exec_())
Note: The QFrame does not have a certain height because its task is to take the task of the content, in this case there is not so we must establish a fixed size, if you are going to add elements to the QFrame do it through a layout and eliminate the line of setFixedHeight().

PyQt: Changing cursor when hovering a button

I'm trying to make a button (or any other Qwidget), That will change users cursor when hovered.
So for instance, when i hover QPushButton, it will change cursor from Arrow to Pointing Hand.
I am using Qt Style Sheet, so i'm not entirely sure, but is there any way to do something like that there?, should look something like this:
btn.setStyleSheet("#btn {background-image: url(':/images/Button1.png'); border: none; }"
"#btn:hover { change-cursor: cursor('PointingHand'); }
Note: Code above is for example, second line will have no functionality at all.
However, if not, if there any other way i can achieve this?

For anyone who wants to achieve this in PyQt5, this is how I managed to do it. Let's say you have a button and you want your cursor to change to the 'PointingHandCursor' when you hover over the button.
You can do it with your_button.setCursor(QCursor(QtCore.Qt.PointingHandCursor)). For example:
from PyQt5.QtWidgets import QWidget, QApplication, QPushButton, QLabel, QProgressBar,
QLineEdit, QFileDialog
from PyQt5 import QtGui, QtCore
from PyQt5.QtGui import QCursor
import sys
class Window(QWidget):
def __init__(self):
super().__init__()
self.title = "your_title"
self.screen_dim = (1600, 900)
self.width = 650
self.height = 400
self.left = int(self.screen_dim[0]/2 - self.width/2)
self.top = int(self.screen_dim[1]/2 - self.height/2)
self.init_window()
def init_window(self):
self.setWindowIcon(QtGui.QIcon('path_to_icon.png'))
self.setWindowTitle(self.title)
self.setGeometry(self.left, self.top, self.width, self.height)
self.setStyleSheet('background-color: rgb(52, 50, 51);')
self.create_layout()
self.show()
def create_layout(self):
self.button = QPushButton('Click Me', self)
self.button.setCursor(QCursor(QtCore.Qt.PointingHandCursor))
if __name__ == '__main__':
App = QApplication(sys.argv)
window = Window()
sys.exit(App.exec())

Use QWidget.setCursor (self, QCursor)
http://pyqt.sourceforge.net/Docs/PyQt4/qwidget.html#setCursor
http://doc.qt.io/qt-4.8/qwidget.html#cursor-prop

For Pyqt6 you can use this code:
from PyQt6.QtCore import Qt
from PyQt6.QtGui import QCursor
closeBtn = QPushButton("X")
closeBtn.setCursor(QCursor(Qt.CursorShape.PointingHandCursor))