[FIXED] pyqt5: some widgets are disappear in my label

Issue

I am implement my-self label, but some widget is disappear.

My code is:

from PyQt5.QtWidgets import *
import sys


class TypeManagerLabel(QLabel):


    def __init__(self):
        super().__init__()

        layout = QVBoxLayout()
        self.setLayout(layout)

        btnLayout = QHBoxLayout()
        self.__nameLineEdit = QLineEdit()
        self.__opBtn = QPushButton('Add/Remove')
        self.__colorBtn = QPushButton('Color')
        btnLayout.addWidget(self.__nameLineEdit)
        btnLayout.addWidget(self.__opBtn)
        layout.addLayout(btnLayout)


class MyWin(QLabel):

    def __init__(self):
        super().__init__()

        layout = QVBoxLayout()
        self.setLayout(layout)

        lab1 = TypeManagerLabel()
        layout.addWidget(lab1)
        # layout.addStretch()
        lab2 = QPushButton('test')
        layout.addWidget(lab2)

app = QApplication(sys.argv)
dialog = MyWin()
dialog.show()
app.exec_()

Currently, the label is OK, and the result should be:

Now, I want the QLineEdit should be located on the top of the label, thus I add a stretch. And the code is:

class MyWin(QLabel):

    def __init__(self):
        super().__init__()

        layout = QVBoxLayout()
        self.setLayout(layout)

        lab1 = TypeManagerLabel()
        layout.addWidget(lab1)
        layout.addStretch()  ###################### add the stretch
        lab2 = QPushButton('test')
        layout.addWidget(lab2)

And the result is:

In the above figure, the QLineEdit is disappeared.

@

My environment is:

win 10
python 3.7.8
pyqt5 5.14.0

---

--------------------------------update ----------------------------------

Thank for the suggestion from musicamante and Heike, subclass QWidget instead of QLabel. But the new bug is reported after I add some new widget. The code is:

from PyQt5.QtWidgets import *
import sys


class TypeManagerLabel(QWidget):

    def __init__(self):
        super().__init__()

        layout = QVBoxLayout()
        self.setLayout(layout)

        btnLayout = QHBoxLayout()
        self.__nameLineEdit = QLineEdit()
        self.__opBtn = QPushButton('Add')
        btnLayout.addWidget(self.__nameLineEdit)
        btnLayout.addWidget(self.__opBtn)

        layout.addLayout(btnLayout)

        infoLabel = QLabel()
        layout.addWidget(infoLabel)

        self.__infoLayout = QVBoxLayout()
        infoLabel.setLayout(self.__infoLayout)

        self.__opBtn.clicked.connect(self.addRemoveSlot)


    def addRemoveSlot(self, checked=False):

        name = self.__nameLineEdit.text()
        layout = QHBoxLayout()
        checkBox = QCheckBox()
        lineEdit = QLineEdit(name)
        layout.addWidget(checkBox)
        layout.addWidget(lineEdit)
        self.__infoLayout.addLayout(layout)


class MyWin(QLabel):

    def __init__(self):
        super().__init__()

        layout = QVBoxLayout()
        self.setLayout(layout)

        lab1 = TypeManagerLabel()
        layout.addWidget(lab1)
        # layout.addStretch()
        lab2 = QPushButton('test')
        layout.addWidget(lab2)

app = QApplication(sys.argv)
dialog = MyWin()
dialog.show()
app.exec_()

When I input a string in the QLineEdit, and click the "Add" button, the result is:

The above figure is what I expected.

But if I add stretch with the code:

class MyWin(QLabel):

    def __init__(self):
        super().__init__()

        layout = QVBoxLayout()
        self.setLayout(layout)

        lab1 = TypeManagerLabel()
        layout.addWidget(lab1)
        layout.addStretch() ###################### add the stretch
        lab2 = QPushButton('test')
        layout.addWidget(lab2)

Then, if I input a string in the QLineEdit and click the 'Add' button, the expected widget would not appear.

Solution

QLabel is a very special type of widget. While it seems very simple, it is not: it has its own behavior when dealing with sizes, and that's in order to accomodate all requirements a widget that is primarily based on (possibly) variable text size, not only horizontally, but vertically also.

That said, one should never try to add layouts and child widgets to classes that are not intended to be used as container, most importantly it should not be done on widgets with peculiar behavior like QLabel.
Using such a widget to contain other widgets is not only a very bad idea, but also completely useless, as you're not actually using the real features a QLabel provides (showing text or images).

To add children and layouts, just use a nested layout, a plain QWidget class, or any other container widgets like QGroupBox or QFrame.

Even after the comments, you're still trying to add widgets to a QLabel. Remove that label, and just add the layout to the main one.

class TypeManagerLabel(QWidget):
    def __init__(self):
        super().__init__()
        # ...

        layout.addLayout(btnLayout)

        self.__infoLayout = QVBoxLayout()
        layout.addLayout(self.__infoLayout)

        self.__opBtn.clicked.connect(self.addRemoveSlot)

    # ...

Answered By - musicamante