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How to visualize my QtWidgets.QToolButton

Hello I have this code using python and pyqt5 which allows to display a graphical interface :
import sys
from PyQt5 import QtCore, QtWidgets
class TabPage(QtWidgets.QWidget):
def __init__(self, parent=None):
super().__init__(parent)
group = QtWidgets.QGroupBox('Monty Python')
layout = QtWidgets.QVBoxLayout(self)
layout.addWidget(group)
grid = QtWidgets.QGridLayout(group)
grid.addWidget(QtWidgets.QLabel('Enter a name:'), 0, 0)
grid.addWidget(QtWidgets.QLabel('Choose a number:'), 0, 1)
grid.addWidget(QtWidgets.QLineEdit(), 1, 0)
grid.addWidget(QtWidgets.QComboBox(), 1, 1)
grid.addWidget(QtWidgets.QPushButton('Click Me!'), 1, 2)
grid.addWidget(QtWidgets.QSpinBox(), 2, 0)
grid.addWidget(QtWidgets.QPushButton('Clear Text'), 2, 2)
grid.addWidget(QtWidgets.QTextEdit(), 3, 0, 1, 3)
class Window(QtWidgets.QWidget):
def __init__(self):
super().__init__()
self.tabs = QtWidgets.QTabWidget()
layout = QtWidgets.QVBoxLayout(self)
layout.addWidget(self.tabs)
button = QtWidgets.QToolButton()
button.setToolTip('Add New Tab')
button.clicked.connect(self.addNewTab)
button.setIcon(self.style().standardIcon(
QtWidgets.QStyle.SP_DialogYesButton))
self.tabs.setCornerWidget(button, QtCore.Qt.TopRightCorner)
button1 = QtWidgets.QToolButton()
button1.setToolTip('Remove')
button1.clicked.connect(self.addNewTab)
button1.setIcon(self.style().standardIcon(
QtWidgets.QStyle.SP_BrowserStop))
self.tabs.setCornerWidget(button1, QtCore.Qt.TopRightCorner)
self.addNewTab()
def addNewTab(self):
text = 'Tab %d' % (self.tabs.count() + 1)
self.tabs.addTab(TabPage(self.tabs), text)
if __name__ == '__main__':
app = QtWidgets.QApplication(sys.argv)
window = Window()
window.setGeometry(600, 100, 300, 200)
window.show()
sys.exit(app.exec_())
When I execute my code I get this :
whereas I would like to get something like this :
How can I do to do this ?
Thank you a lot !

QTabWidget::setCornerWidget(QWidget *widget, Qt::Corner corner = Qt::TopRightCorner)
Any previously set corner widget is hidden. https://doc.qt.io/qt-5/qtabwidget.html#setCornerWidget
Try it:
import sys
from PyQt5 import QtCore, QtWidgets
class TabPage(QtWidgets.QWidget):
def __init__(self, parent=None):
super().__init__(parent)
group = QtWidgets.QGroupBox('Monty Python')
layout = QtWidgets.QVBoxLayout(self)
layout.addWidget(group)
grid = QtWidgets.QGridLayout(group)
grid.addWidget(QtWidgets.QLabel('Enter a name:'), 0, 0)
grid.addWidget(QtWidgets.QLabel('Choose a number:'), 0, 1)
grid.addWidget(QtWidgets.QLineEdit(), 1, 0)
grid.addWidget(QtWidgets.QComboBox(), 1, 1)
grid.addWidget(QtWidgets.QPushButton('Click Me!'), 1, 2)
grid.addWidget(QtWidgets.QSpinBox(), 2, 0)
grid.addWidget(QtWidgets.QPushButton('Clear Text'), 2, 2)
grid.addWidget(QtWidgets.QTextEdit(), 3, 0, 1, 3)
class Window(QtWidgets.QWidget):
def __init__(self):
super().__init__()
self.tabs = QtWidgets.QTabWidget()
self.tabs.setTabsClosable(True) # +
self.tabs.tabCloseRequested.connect(self.qtabwidget_tabcloserequested) # +
self.tabs.currentChanged.connect(lambda: print(f'currentIndex->{self.tabs.currentIndex()}')) #+
layout = QtWidgets.QVBoxLayout(self)
layout.addWidget(self.tabs)
button = QtWidgets.QToolButton()
button.setFixedSize(20, 20) # +
button.setToolTip('Add New Tab')
button.clicked.connect(self.addNewTab)
button.setIcon(self.style().standardIcon(
QtWidgets.QStyle.SP_DialogYesButton))
# self.tabs.setCornerWidget(button, QtCore.Qt.TopRightCorner)
button1 = QtWidgets.QToolButton()
button1.setFixedSize(20, 20) # +
button1.setToolTip('Remove')
button1.clicked.connect(self.removeTab) # removeTab
button1.setIcon(self.style().standardIcon(
QtWidgets.QStyle.SP_BrowserStop))
# Any previously set corner widget is hidden.
# self.tabs.setCornerWidget(button1, QtCore.Qt.TopRightCorner) #
# +++ vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
self.widget = QtWidgets.QWidget()
h_layout = QtWidgets.QHBoxLayout(self.widget)
h_layout.setContentsMargins(0, 0, 0, 0)
h_layout.addWidget(button)
h_layout.addWidget(button1)
self.tabs.setCornerWidget(self.widget, QtCore.Qt.TopRightCorner)
# +++ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
self.addNewTab()
def addNewTab(self):
text = 'Tab %d' % (self.tabs.count() + 1)
self.tabs.addTab(TabPage(self.tabs), text)
#QtCore.pyqtSlot(int)
def qtabwidget_tabcloserequested(self, index):
# gets the widget
widget = self.tabs.widget(index)
# if the widget exists
if widget:
# removes the widget
widget.deleteLater()
# removes the tab of the QTabWidget
self.tabs.removeTab(index)
def removeTab(self):
print('def removeTab(self): print')
if __name__ == '__main__':
app = QtWidgets.QApplication(sys.argv)
window = Window()
window.setGeometry(600, 100, 300, 200)
window.show()
sys.exit(app.exec_())

Since the other answer does not explain the cause of the problem and its code is confusing, I will explain the error in detail.
The error is that there can only be one cornerWidget, if you set a second cornerWidget it will replace the previous one, therefore only one QToolButton is observed. If you want to show several widgets then you have to use a container like a QWidget and place the other widgets there.
# ...
layout.addWidget(self.tabs)
button = QtWidgets.QToolButton()
button.setToolTip("Add New Tab")
button.clicked.connect(self.addNewTab)
button.setIcon(self.style().standardIcon(QtWidgets.QStyle.SP_DialogYesButton))
button1 = QtWidgets.QToolButton()
button1.setToolTip("Remove")
button1.clicked.connect(self.addNewTab)
button1.setIcon(self.style().standardIcon(QtWidgets.QStyle.SP_BrowserStop))
container = QtWidgets.QWidget()
container.setContentsMargins(0, 0, 0, 0)
lay = QtWidgets.QHBoxLayout(container)
lay.setContentsMargins(0, 0, 0, 0)
lay.addWidget(button)
lay.addWidget(button1)
self.tabs.setCornerWidget(container, QtCore.Qt.TopRightCorner)
self.addNewTab()

How can I make a QWidget open after a QWidget closes?

I have the below code:
import os
from functools import partial
import numpy as np
from PyQt5 import QtCore, QtWidgets
class MainWidget(QtWidgets.QWidget):
def __init__(self, parent=None):
super().__init__(parent)
self.resize(500, 500)
self.setWindowFlags(
self.windowFlags() | QtCore.Qt.MSWindowsFixedSizeDialogHint
)
self.setWindowTitle("nCode analysis set-up")
self.wait_window = WaitWindow()
thread = QtCore.QThread(self)
thread.start()
self.m_worker = Worker()
self.m_worker.moveToThread(thread)
self.m_worker.new_content_signal.connect(self.get_content)
# Creating the top level grid layout
mainGrid = QtWidgets.QGridLayout(self)
self.analysis_type_label = QtWidgets.QLabel(self)
self.analysis_type_label.setText("Type of analysis")
mainGrid.addWidget(self.analysis_type_label, 0, 0)
self.analysis_type_combo = QtWidgets.QComboBox(self)
self.analysis_type_combo.addItems(["Fatigue", "Proof plus fatigue"])
mainGrid.addWidget(self.analysis_type_combo, 0, 1, 1, 2)
self.load_deck_type_label = QtWidgets.QLabel(self)
self.load_deck_type_label.setText("Type of fatigue deck")
mainGrid.addWidget(self.load_deck_type_label, 1, 0)
self.load_deck_type_combo = QtWidgets.QComboBox(self)
self.load_deck_type_combo.addItems(
["Regen braking", "No regen braking"]
)
mainGrid.addWidget(self.load_deck_type_combo, 1, 1, 1, 2)
self.analysis_engine_type_label = QtWidgets.QLabel(self)
self.analysis_engine_type_label.setText("Analysis Engine")
mainGrid.addWidget(self.analysis_engine_type_label, 2, 0)
self.analysis_engine_type_combo = QtWidgets.QComboBox(self)
self.analysis_engine_type_combo.addItems(["EN analysis", "SN analysis"])
mainGrid.addWidget(self.analysis_engine_type_combo, 2, 1, 1, 2)
# Creating a scrolable area to accommodate for a large number of components with possible lenghty names
self.scrollArea = QtWidgets.QScrollArea(self)
# The line below is absolutely required to make the scrollable area work.
self.scrollArea.setWidgetResizable(True)
mainGrid.addWidget(self.scrollArea, 3, 0, 1, 3)
self.secondaryWidget = QtWidgets.QWidget()
self.scrollArea.setWidget(self.secondaryWidget)
self.secondaryGrid = QtWidgets.QGridLayout(self.secondaryWidget)
self.createDCL = QtWidgets.QPushButton(self)
self.createDCL.setText("Create DCL")
mainGrid.addWidget(self.createDCL, 4, 0, 1, 3)
def start_task(self):
if not os.path.exists("loading_database.db"):
QtWidgets.QMessageBox.information(
None,
"Loading database missing",
"Loading database has not been found. Creation of a new one will be attempted",
)
# self.loadingDatabaseCreator()
QtWidgets.QMessageBox.information(
None, "Successful", "Loading database succesfully created"
)
filePath, _ = QtWidgets.QFileDialog.getOpenFileName(
None, "Select input model", "", "Input deck (*.inp)", "*.inp"
)
if filePath:
self.wait_window.show()
self.m_worker.finished.connect(self.wait_window.close)
wrapper = partial(self.m_worker.read_file, filePath)
# Launch the task in a reasonable time for the window to show
QtCore.QTimer.singleShot(100, wrapper)
w.show()
self.wait_window.raise_()
self.wait_window.activateWindow()
#QtCore.pyqtSlot(int, str)
def get_content(self, i, content):
label = QtWidgets.QLabel("{} material".format(content))
linedit = QtWidgets.QLineEdit(placeholderText="Drop material name here")
linedit.setFixedWidth(150)
button = QtWidgets.QPushButton("Pick material")
self.secondaryGrid.addWidget(label, 2 + i, 0)
self.secondaryGrid.addWidget(linedit, 2 + i, 1)
self.secondaryGrid.addWidget(button, 2 + i, 2)
class WaitWindow(QtWidgets.QDialog):
def __init__(self):
super().__init__()
self.setWindowTitle("Info")
self.resize(600, 200)
layout = QtWidgets.QVBoxLayout(self)
self.message = QtWidgets.QLabel()
self.message.setFixedWidth(550)
self.message.setText("Please wait while input file is being read")
layout.addWidget(self.message)
class Worker(QtCore.QObject):
finished = QtCore.pyqtSignal()
new_content_signal = QtCore.pyqtSignal(int, str)
#QtCore.pyqtSlot(str)
def read_file(self, fileName):
i = 0
collector_array = []
with open(fileName, "r") as model_file_obj:
for line in model_file_obj.readlines():
if "*ELEMENT," in line and "DCOUP3D" not in line:
t = line.split("ELSET=")[1][:-1]
if t not in collector_array:
self.new_content_signal.emit(i, t)
QtCore.QThread.msleep(10)
collector_array.append(t)
i += 1
self.finished.emit()
if __name__ == "__main__":
import sys
app = QtWidgets.QApplication(sys.argv)
w = MainWidget()
w.start_task()
sys.exit(app.exec_())
It looks like a lot of code but the MainWidget is initialized first. After the initialization the MainWidget function of start_task is called which show's the WaitWindow QDialog, asks the user for the input file which it starts parsing and then shows the MainWidget QWidget window. While this is not too bad I would like the user to not see the MainWidget window until the file has finished parsing and the WaitWindow is closed. Any ideas?

I do not understand why you use w.show(), remove it.
Going to the problem, if you want the MainWidget to show after executing the task, you just have to connect the show method to the finished signal
# ...
self.m_worker.finished.connect(self.wait_window.close)
self.m_worker.finished.connect(self.show)
# ...

Center subwindows in qmdiarea

Is there an attribute to position subwindows in qmdiarea? I’m trying to center subwindow in middle of mainwindow on startup (mdiarea)
I’m working on a mcve but haven’t finished it, wanted to see if anyone has tried doing this, and how they did it
Subwindows are randomly placed on startup when initialized
class App(QMainWindow, Ui_MainWindow):
def __init__(self, parent=None):
QMainWindow.__init__(self, parent=parent)
self.setupUi(self)
self.screenShape = QDesktopWidget().screenGeometry()
self.width = self.screenShape.width()
self.height = self.screenShape.height()
self.resize(self.width * .6, self.height * .6)
self.new = []
#calls GUI's in other modules
self.lw = Login()
self.vs = VS()
self.ms = MS()
self.hw = HomeWindow()
self.mw = MainWindow()
self.ga = GA()
self.sGUI = Settings()
# shows subwindow
self.CreateLogin()
self.CreateVS()
self.CreateMS()
self.CreateGA()
self.CreateSettings()
def CreateLogin(self):
self.subwindow = QMdiSubWindow()
self.subwindow.setWidget(self.lw)
self.subwindow.setAttribute(Qt.WA_DeleteOnClose, True)
self.mdiArea.addSubWindow(self.subwindow)
self.subwindow.setMaximumSize(520, 300)
self.subwindow.setMinimumSize(520, 300)
self.lw.showNormal()
def CreateVS(self):
self.subwindow = QMdiSubWindow()
self.subwindow.setWidget(self.vs)
self.mdiArea.addSubWindow(self.subwindow)
self.vs.showMinimized()
def CreateMS(self):
self.subwindow = QMdiSubWindow()
self.subwindow.setWidget(self.ms)
self.mdiArea.addSubWindow(self.subwindow)
self.ms.showMinimized()
self.ms.tabWidget.setCurrentIndex(0)
def CreateGA(self):
self.subwindow = QMdiSubWindow()
self.subwindow.setWidget(self.ga)
self.mdiArea.addSubWindow(self.subwindow)
self.ga.showMinimized()
self.subwindow.setMaximumSize(820, 650)
def CreateSettings(self):
self.subwindow = QMdiSubWindow()
self.subwindow.setWidget(self.sGUI)
self.mdiArea.addSubWindow(self.subwindow)
self.sGUI.showMinimized()
def CreateWindow(self):
self.hw.pushButton.clicked.connect(self.vs.showNormal)
self.hw.pushButton_2.clicked.connect(self.Moduleprogram)
self.hw.pushButton_3.clicked.connect(self.ms.showNormal)
self.hw.pushButton_4.clicked.connect(self.ga.showNormal)
self.subwindow = QMdiSubWindow()
self.subwindow.setWindowFlags(Qt.CustomizeWindowHint | Qt.Tool)
self.subwindow.setWidget(self.hw)
self.subwindow.setMaximumSize(258, 264)
self.subwindow.move(self.newwidth*.35, self.newheight*.25)
self.mdiArea.addSubWindow(self.subwindow)

In Qt the geometry is only effective when the window is visible so if you want to center something it must be in the showEvent method. On the other hand to center the QMdiSubWindow you must first get the center of the viewport of the QMdiArea, and according to that modify the geometry of the QMdiSubWindow.
Because the code you provide is complicated to execute, I have created my own code
from PyQt5 import QtCore, QtGui, QtWidgets
import random
def create_widget():
widget = QtWidgets.QLabel(
str(random.randint(0, 100)), alignment=QtCore.Qt.AlignCenter
)
widget.setStyleSheet(
"""background-color: {};""".format(
QtGui.QColor(*random.sample(range(255), 3)).name()
)
)
widget.setMinimumSize(*random.sample(range(100, 300), 2))
return widget
class MainWindow(QtWidgets.QMainWindow):
def __init__(self, parent=None):
super().__init__(parent)
add_button = QtWidgets.QPushButton(
"Add subwindow", clicked=self.add_subwindow
)
self._mdiarea = QtWidgets.QMdiArea()
central_widget = QtWidgets.QWidget()
self.setCentralWidget(central_widget)
lay = QtWidgets.QVBoxLayout(central_widget)
lay.addWidget(add_button)
lay.addWidget(self._mdiarea)
self._is_first_time = True
for _ in range(4):
self.add_subwindow()
#QtCore.pyqtSlot()
def add_subwindow(self):
widget = create_widget()
subwindow = QtWidgets.QMdiSubWindow(self._mdiarea)
subwindow.setWidget(widget)
subwindow.setAttribute(QtCore.Qt.WA_DeleteOnClose, True)
subwindow.show()
self._mdiarea.addSubWindow(subwindow)
# self.center_subwindow(subwindow)
def showEvent(self, event):
if self.isVisible() and self._is_first_time:
for subwindow in self._mdiarea.subWindowList():
self.center_subwindow(subwindow)
self._is_first_time = False
def center_subwindow(self, subwindow):
center = self._mdiarea.viewport().rect().center()
geo = subwindow.geometry()
geo.moveCenter(center)
subwindow.setGeometry(geo)
if __name__ == "__main__":
import sys
app = QtWidgets.QApplication(sys.argv)
w = MainWindow()
w.show()
sys.exit(app.exec_())
Update:
If you want the subwindow to be centered then with the following code you have to create a property center to True:
def add_subwindow(self):
widget = create_widget()
subwindow = QtWidgets.QMdiSubWindow(self._mdiarea)
subwindow.setWidget(widget)
subwindow.setAttribute(QtCore.Qt.WA_DeleteOnClose, True)
subwindow.show()
subwindow.setProperty("center", True) # <----
self._mdiarea.addSubWindow(subwindow)
def showEvent(self, event):
if self.isVisible() and self._is_first_time:
for subwindow in self._mdiarea.subWindowList():
if subwindow.property("center"): # <---
self.center_subwindow(subwindow)
self._is_first_time = False

How to set property of QTextCharFormat in PyQt?

I am trying to set a custom property of an image inserted into a QTextEdit. I have the following example code which sets then outputs the value of the property to the terminal:
import sys
from PyQt5.QtWidgets import *
from PyQt5.QtGui import *
class TestEditor(QWidget):
def __init__(self):
QWidget.__init__(self)
layout = QVBoxLayout()
self.setLayout(layout)
self.layout().setSpacing(0)
self.layout().setContentsMargins(0, 0, 0, 0)
self.textEdit = QTextEdit()
self.layout().addWidget(self.textEdit)
document = self.textEdit.document()
cursor = QTextCursor(document)
cursor.insertImage("./testimage.png")
f = cursor.charFormat()
print(f)
prop_id = 0x100000 + 1
f.setProperty(prop_id, 100)
print(f.intProperty(prop_id))
print('------')
block = document.firstBlock()
while block.length() > 0:
print(block)
it = block.begin()
while not it.atEnd():
f = it.fragment()
fmt = f.charFormat()
print(fmt)
print(fmt.intProperty(prop_id))
it += 1
block = block.next()
class TestWindow(QWidget):
def __init__(self):
QWidget.__init__(self)
self.initUi()
def initUi(self):
layout = QVBoxLayout()
layout.addWidget(HextEditor())
self.setLayout(layout)
self.layout().setSpacing(0)
self.layout().setContentsMargins(0, 0, 0, 0)
self.setWindowTitle('button tooltip')
self.show()
def main():
app = QApplication(sys.argv)
window = TestWindow()
sys.exit(app.exec_())
if __name__ == '__main__':
main()
The program results in an output of:
<PyQt5.QtGui.QTextCharFormat object at 0x107109ba8>
100
------
<PyQt5.QtGui.QTextBlock object at 0x105448318>
<PyQt5.QtGui.QTextCharFormat object at 0x107109ba8>
0
Note that the second time the value is gotten it has a value of 0 rather than 100. It even appears to be the same instance of a QTextCharFormat. How would I accomplish something like this? Am I missing something simple here?

I solved this by saving the range of the inserted image, selecting it, and using QTextCursor.setCharFormat() to save the changes:
import sys
from PyQt5.QtWidgets import *
from PyQt5.QtGui import *
class TestEditor(QWidget):
def __init__(self):
QWidget.__init__(self)
layout = QVBoxLayout()
self.setLayout(layout)
self.layout().setSpacing(0)
self.layout().setContentsMargins(0, 0, 0, 0)
self.textEdit = QTextEdit()
self.layout().addWidget(self.textEdit)
document = self.textEdit.document()
cursor = QTextCursor(document)
# Save the position of the beginning and end of the inserted image
p1 = cursor.position()
cursor.insertImage("./testimage.png")
p2 = cursor.position()
f = cursor.charFormat()
print(f)
prop_id = 0x100000 + 1
f.setProperty(prop_id, 100)
# Select the inserted fragment and apply format
cursor.setPosition(p1)
cursor.setPosition(p2, QTextCursor.KeepAnchor)
cursor.setCharFormat(f)
print(f.intProperty(prop_id))
print('------')
block = document.firstBlock()
while block.length() > 0:
print(block)
it = block.begin()
while not it.atEnd():
f = it.fragment()
fmt = f.charFormat()
print(fmt)
print(fmt.intProperty(prop_id))
it += 1
block = block.next()
class TestWindow(QWidget):
def __init__(self):
QWidget.__init__(self)
self.initUi()
def initUi(self):
layout = QVBoxLayout()
layout.addWidget(TestEditor())
self.setLayout(layout)
self.layout().setSpacing(0)
self.layout().setContentsMargins(0, 0, 0, 0)
self.setWindowTitle('button tooltip')
self.show()
def main():
app = QApplication(sys.argv)
window = TestWindow()
sys.exit(app.exec_())
if __name__ == '__main__':
main()

What happens with QMainWindow

I want to create the GUI with this code. When i click Add New Object Button, it will show the pop up (I use QMainWindown) but i want to put the QLabel in here, it can not work
I dont know why.i hope everyone can give me more some advices. Thanks you
This is my code :
from PySide import QtCore, QtGui
import sys
app = QtGui.QApplication.instance()
if not app:
app = QtGui.QApplication([])
class Window(QtGui.QDialog):
def __init__(self, parent=None):
super(Window, self).__init__(parent)
self.mainLayout = QtGui.QGridLayout()
self.mainLayout.addWidget(self.First(), 0, 0, 2, 0)
self.setLayout(self.mainLayout)
self.setWindowTitle("Library")
self.resize(700,660)
#----------------------------------------FIRST COLUMN-------------------------------------
def First(self):
FirstFrame = QtGui.QFrame()
FirstFrame.setFixedSize(230,700)
# LABEL
renderer_lb = QtGui.QLabel("Renderer :")
folders_lb = QtGui.QLabel("Folder :")
#COMBOBOX
self.renderer_cbx = QtGui.QComboBox()
self.renderer_cbx.addItem("Vray")
self.renderer_cbx.addItem("Octane")
# LIST VIEW FOLDER
self.folders_lv = QtGui.QListView()
# BUTTON
addnewobject_btn = QtGui.QPushButton("Add New Objects")
newset_btn = QtGui.QPushButton("New Set")
# DEFINE THE FUNCTION FOR FIRST FRAME
Firstbox = QtGui.QGridLayout()
Firstbox.addWidget(renderer_lb,0,0)
Firstbox.addWidget(folders_lb,2,0,1,4)
Firstbox.addWidget(self.renderer_cbx,0,1,1,3)
Firstbox.addWidget(self.folders_lv,3,0,1,4)
Firstbox.addWidget(addnewobject_btn,4,0,1,2)
Firstbox.addWidget(newset_btn,4,3)
Firstbox.setColumnStretch(1, 1)
FirstFrame.setLayout(Firstbox)
addnewobject_btn.clicked.connect(self.addnewobject)
return FirstFrame
def addnewobject(self):
window = QtGui.QMainWindow(self)
window.setWindowTitle('Select folder of new objects')
window.setFixedSize(450,90)
window.show()
folder_lb = QtGui.QLabel("Folder : ")
browser = QtGui.QGridLayout()
browser.addWidget(folder_lb,0,0)
window.setLayout(browser)
if __name__ == '__main__':
window = Window()
sys.exit(window.exec_())

Just as you did in the First() function, you could create an homemade widget using QFrame. Then you can set a central widget for your new window.
from PySide import QtCore, QtGui
import sys
app = QtGui.QApplication.instance()
if not app:
app = QtGui.QApplication([])
class Window(QtGui.QDialog):
def __init__(self, parent=None):
super(Window, self).__init__(parent)
self.mainLayout = QtGui.QGridLayout()
self.mainLayout.addWidget(self.First(), 0, 0, 2, 0)
self.setLayout(self.mainLayout)
self.setWindowTitle("Library")
self.resize(700,660)
self.show()
#----------------------------------------FIRST COLUMN-------------------------------------
def First(self):
FirstFrame = QtGui.QFrame()
FirstFrame.setFixedSize(230,700)
# LABEL
renderer_lb = QtGui.QLabel("Renderer :")
folders_lb = QtGui.QLabel("Folder :")
#COMBOBOX
self.renderer_cbx = QtGui.QComboBox()
self.renderer_cbx.addItem("Vray")
self.renderer_cbx.addItem("Octane")
# LIST VIEW FOLDER
self.folders_lv = QtGui.QListView()
# BUTTON
addnewobject_btn = QtGui.QPushButton("Add New Objects")
newset_btn = QtGui.QPushButton("New Set")
# DEFINE THE FUNCTION FOR FIRST FRAME
Firstbox = QtGui.QGridLayout()
Firstbox.addWidget(renderer_lb,0,0)
Firstbox.addWidget(folders_lb,2,0,1,4)
Firstbox.addWidget(self.renderer_cbx,0,1,1,3)
Firstbox.addWidget(self.folders_lv,3,0,1,4)
Firstbox.addWidget(addnewobject_btn,4,0,1,2)
Firstbox.addWidget(newset_btn,4,3)
Firstbox.setColumnStretch(1, 1)
FirstFrame.setLayout(Firstbox)
addnewobject_btn.clicked.connect(self.addnewobject)
return FirstFrame
def addnewobject(self):
secondFrame = QtGui.QFrame()
secondFrame.setFixedSize(230,700)
# LABEL
folders_lb = QtGui.QLabel("Folder :")
# DEFINE THE FUNCTION FOR FIRST FRAME
secondGridLayout = QtGui.QGridLayout()
secondGridLayout.addWidget(folders_lb,2,0,1,4)
secondGridLayout.setColumnStretch(1, 1)
secondFrame.setLayout(secondGridLayout)
window = QtGui.QMainWindow(self)
window.setWindowTitle('Select folder of new objects')
window.setFixedSize(600,700)
window.setCentralWidget(secondFrame) # Here is the main change: setLayout(QLayout) to setCentralWidget(QWidget)
window.show()
if __name__ == '__main__':
window = Window()
sys.exit(window.exec_())
Is this intended for Maya? If yes, I recommand you not to use modal windows as it will quickly fed up the users.