在任何情况下如何拉伸 QTableWidget 最后一列

Question

How make the last column always strech to the remaining space?

Here what I don't want to see

Here the code I'm using:

import sys
from PyQt5.QtWidgets import *

class MainWindow(QMainWindow):
    def __init__(self):
        super().__init__()
        self.resize(300, 300)
        self.show()

        self.tableWidget = QTableWidget()
        self.setCentralWidget(self.tableWidget)

        self.tableWidget.setColumnCount(2)
        self.tableWidget.setHorizontalHeaderLabels(["column 1", "column 2"])
        self.tableWidget.setStyleSheet("QHeaderView::section{Background-color:cyan;}")
        self.tableWidget.setSortingEnabled(True)

        nb = 25
        self.tableWidget.setRowCount(nb)
        for i in range(nb):
            self.tableWidget.setItem(i, 0, QTableWidgetItem("A"*(nb-i)))
            self.tableWidget.setItem(i, 1, QTableWidgetItem("B"*(nb-i)))
        
        self.tableWidget.resizeColumnsToContents()
        self.tableWidget.horizontalHeader().setStretchLastSection(True)

app = QApplication(sys.argv)
window = MainWindow()
sys.exit(app.exec_())

And here how to reproduce that unwanted behaviour: launch the prog, scroll right the horizontal scrollbar, then resize a bit horizontally the width of the window

Answer 1

It seems like a small bug in the updateGeometries code, which doesn't update the header offset when the visible columns remain the same and the scroll mode is ScrollPerItem ; this also happens for the vertical header, but it's usually less noticeable since rows are generally smaller.
Note that the issue is also present even without resizing columns (or rows) to contents, the problem is always present whenever at least two sections are visible and don't fit the view, causing the scroll bar to show.

A possible solution is to subclass the table, override the resizeEvent() and call setOffsetToLastSection() whenever required. Theoretically it should be done in the updateGeometries call, but considering that this only happens when resizing (and updateGeometries gets called very often) I doubt it would make a lot of sense.
It's probably a good idea to do some more experiments and research to ensure that the checks on the scroll mode and scrollbars are enough, and eventually submit a bug .

class MyTable(QtWidgets.QTableWidget):
    def resizeEvent(self, event):
        checkHorizontal = (self.horizontalScrollMode() == self.ScrollPerItem and 
            self.horizontalScrollBar().maximum() >= 1 and 
            self.horizontalScrollBar().value() == self.horizontalScrollBar().maximum())
        checkVertical = (self.verticalScrollMode() == self.ScrollPerItem and 
            self.verticalScrollBar().maximum() >= 1 and 
            self.verticalScrollBar().value() == self.verticalScrollBar().maximum())
        super().resizeEvent(event)
        if checkHorizontal:
            self.horizontalHeader().setOffsetToLastSection()
        if checkVertical:
            self.verticalHeader().setOffsetToLastSection()

If you plan to use lots of tables and subclasses, and you want to always use this behavior, you could do a small "hack" by directly patching the QTableView class (since it's what QTableWidget inherits from); note that this must be done in as soon as the class' module is imported (so, at the very beginning of your main script, right after importing QtWidgets for the very first time):

# create a new reference for the default implementation
QTableView._resizeEvent = QTableView.resizeEvent
# the general fix
def resizeEventFix(self, event):
    checkHorizontal = (self.horizontalScrollMode() == self.ScrollPerItem and 
        self.horizontalScrollBar().maximum() >= 1 and 
        self.horizontalScrollBar().value() == self.horizontalScrollBar().maximum())
    checkVertical = (self.verticalScrollMode() == self.ScrollPerItem and 
        self.verticalScrollBar().maximum() >= 1 and 
        self.verticalScrollBar().value() == self.verticalScrollBar().maximum())
    # call the original implementation we renamed before
    QTableView._resizeEvent(self, event)
    if checkHorizontal:
        self.horizontalHeader().setOffsetToLastSection()
    if checkVertical:
        self.verticalHeader().setOffsetToLastSection()
# apply the fix
QTableView.resizeEvent = resizeEventFix

The above trick is actually very useful when using UIs created in Designer, as it allows to fix/patch standard Qt classes without the need to always promote them: as long as objects are created with public functions (calls that could be intercepted by PyQt, not objects Qt creates with private methods), those classes will always be "patched". In this case it can be also useful for the suggested testing, you can create a certain amount of possible tables in Designer and then easily test them against the above fix.