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I am working on a PyQt5 project, which needs a folder viewer by PyQt5 QTreeView. In order to put more stuff, I try to change the size of the tree view but in vain. Here is the code from Pythonspot:

import sys
from PyQt5.QtWidgets import QApplication, QFileSystemModel, QTreeView, QWidget, QVBoxLayout
from PyQt5.QtGui import QIcon

class App(QWidget):

 def __init__(self):
 super().__init__()
 self.title = 'PyQt5 file system view - pythonspot.com'
 self.left = 10
 self.top = 10
 self.width = 640
 self.height = 480
 self.initUI()

 def initUI(self):
 self.setWindowTitle(self.title)
 self.setGeometry(self.left, self.top, self.width, self.height)

 self.model = QFileSystemModel()
 self.model.setRootPath('')
 self.tree = QTreeView()
 self.tree.setModel(self.model)

 self.tree.setAnimated(False)
 self.tree.setIndentation(20)
 self.tree.setSortingEnabled(True)

 self.tree.setWindowTitle("Dir View")
 self.tree.resize(640, 200)

 windowLayout = QVBoxLayout()
 windowLayout.addWidget(self.tree)
 self.setLayout(windowLayout)

 self.show()

if __name__ == '__main__':
 app = QApplication(sys.argv)
 ex = App()
 sys.exit(app.exec_())

I change the tree view by

self.tree.resize(640, 200)

Why it does not function?

A layout is used to establish the position and size of the widget you are using, so in your case even if you use resize the size will not be changed, instead you should set a fixed size so the layout can not change the size of the QTreeView.

import sys
from PyQt5 import QtCore, QtGui, QtWidgets

class App(QtWidgets.QWidget):
 def __init__(self):
 super().__init__()
 self.title = 'PyQt5 file system view - pythonspot.com'
 self.left, self.top, self.width, self.height = 10, 10, 640, 480
 self.initUI()

 def initUI(self):
 self.setWindowTitle(self.title)
 self.setGeometry(self.left, self.top, self.width, self.height)

 self.model = QtWidgets.QFileSystemModel()
 self.model.setRootPath('')
 self.tree = QtWidgets.QTreeView()
 self.tree.setModel(self.model)

 self.tree.setAnimated(False)
 self.tree.setIndentation(20)
 self.tree.setSortingEnabled(True)

 self.tree.setWindowTitle("Dir View")
 self.tree.setFixedSize(640, 200)

 windowLayout = QtWidgets.QVBoxLayout(self)
 windowLayout.addWidget(self.tree, alignment=QtCore.Qt.AlignTop)

 self.show()

if __name__ == '__main__':
 app = QtWidgets.QApplication(sys.argv)
 ex = App()
 sys.exit(app.exec_())