How to load a file in PyQt4? [duplicate] - python

This question already has answers here:
How can I add a Picture to a QWidget in PyQt4
(3 answers)
Closed 4 years ago.
everyone! I am currently attempting to make a program that will load/display images. So far, I have successfully created a button with the ability to browse and select your file. However, I do not know what to do after that. My goal for this, is to at least successfully load and display an image. I am still very new to programming, but am willing to learn! Thank you, so much!
Below, is the code I have created. I really just need to help as to what I am supposed to do next. I am lost as to what functions I am supposed to write next. Thanks!
__author__ = 'Jay'
import sys
from PyQt4 import QtGui, QtCore
class Window(QtGui.QMainWindow):
def __init__(self):
super(Window, self).__init__()
self.setGeometry(0, 0, 500, 500)
self.setWindowTitle('Laser Scan')
self.setWindowIcon(QtGui.QIcon('Laser.png'))
self.home()
self.show()
def home(self):
btn = QtGui.QPushButton("Select File...", self)
btn.clicked.connect(self.file_open)
btn.resize(100, 25)
btn.move(0, 10)
self.show()
def file_open(self):
name = QtGui.QFileDialog.getOpenFileName(self, 'Open File')
file = open(name, 'r')
def run():
app = QtGui.QApplication(sys.argv)
GUI = Window()
sys.exit(app.exec_())
run()

Showing an image from a file is pretty easy in Qt. You just need to find the right widget. In this case I suggest you use a QLabel. This can display a QPixmap and that includes the code necessary to construct from a file:
def file_open(self):
name = QtGui.QFileDialog.getOpenFileName(self, 'Open File')
qp = QtGui.QPixmap(name)
self.ql = QtGui.QLabel(None)
self.ql.setPixmap(qp)
self.ql.move(200,200)
self.ql.show()
Note the way that I assign the QLabel to an instance variable self.ql here: because it is a top-level window, it is not parented in the QObject hierarchy and so it will immediately be garbage collected if we don't hold on to a reference to it. In any case, we'll want that reference in the future if we intend to do anything with the new widget.
However, your code hints that you want to show the image inside the top level window you have already constructed. That is not particularly hard: you can just add it to the parent window like the button. However, you will then need to lay out this window more dynamically. For example, a QVBoxLayout might be appropriate here.

Related

PySide2 main window not working after pop-up

I am building a graphical interface for an application using PySide2. My main window is a QMainWindow and I am trying to open a pop-up window, which is a QDialog, whenever a specific action is performed on the main window.
The pop-up opens perfectly fine. However, after it is open, the main window is no longer responsive. I believe the problem is that my application is overwriting the main window with the popup window.
The error message whenever I try to change the main window's stackedWidget index is:
AttributeError: 'Ui_popupHideSuccess' object has no attribute 'stackedWidget'
The code I am using to open the main window is the following:
if __name__ == '__main__':
app = QApplication(sys.argv)
myWindow = MainWindow()
myWindow.show()
sys.exit(app.exec_())
And the code I am using to open the pop-up window is the following:
def showPopupSuccessHide(self):
self.window = QDialog()
self.ui = Ui_popupHideSuccess()
self.ui.setupUi(self.window)
self.window.show()
The code for the windows themselves are on other files (as I am using QtDesigner for developing them). I believe it to be unnecessary for resolving this issue, but I can provide it if needed. What am I doing wrong here? I need to open pop-ups and still interact with the main window after.
I have no idea how to actually resolve this. I believe my error to be in the code I am using to open the pop-up window, but I'm not sure how to tweak it for it to work properly.
TL;DR
Do not overwrite self.ui.
Explanation
How uic composition works
One of the common ways of properly using pyuic generated files is to use composition (as opposed to multiple inheritance):
from PyQt5.QtWidgets import QApplication, QMainWindow, QDialog
from ui_mainWindow import Ui_MainWindow
class MyWindow(QMainWindow):
def __init__(self):
super().__init__()
self.ui = Ui_MainWindow()
self.ui.setupUi(self)
self.ui.myLineEdit.setText('some text')
This is perfectly fine, and makes sense: the concept is that an instance of the pyuic class (sometimes called "form class") is created and then the actual window is "set up" using that instance, with the self.ui object containing references to all widgets.
Note that making the ui persistent (using an instance attribute) is actually not a strict requirement, but it is usually necessary in order to be able to directly access the widgets, which is normally important to create signal connections or read properties.
But, if that's not required, it will work anyway: the widgets are automatically "reparented" to the main window (or their direct parents), and the garbage collection is not an issue as Qt will keep its own references internally (in Qt terms, "the window takes ownership").
Technically speaking, this is completely valid:
class MyWindow(QMainWindow):
def __init__(self):
super().__init__()
Ui_MainWindow().setupUi(self)
Then, we can still access the widgets using findChild and their object names (those set in Designer):
self.findChild(QLineEdit, 'myLineEdit').setText('some text')
Obviously, it is not very practical.
Creating "child" windows
When there is the need to create a child window (usually, a dialog), it's normally suggested to use an instance attribute to avoid garbage collection:
def createWindow(self):
self.window = QDialog()
self.window.show()
If that dialog also has a Designer file, we need to do something similar to what done at the beginning. Unfortunately, a very common mistake is to create the ui instance by using the same name:
def createWindow(self):
self.window = QDialog()
self.ui = Ui_Dialog()
self.ui.setupUi(self.window)
self.ui.anotherLineEdit.setText('another text')
self.window.show()
This is theoretically fine: all works as expected. But there's a huge problem: the above overwrites self.ui, meaning that we lose all references to the widgets of the main window.
Suppose that you want to set the text of the line edit in the dialog based on the text written in that of the main window; the following will probably crash:
def createWindow(self):
self.window = QDialog()
self.ui = Ui_Dialog()
self.ui.setupUi(self.window)
self.ui.anotherLineEdit.setText(self.ui.myLineEdit.text())
self.window.show()
This clearly shows an important aspect: it's mandatory to always think before assigning attributes that may already exist.
In the code here above, this was actually done twice: not only we overwrote the self.ui we created before, but we also did it for window(), which is an existing function of all Qt widgets (it returns the top level ancestor window of the widget on which it was called).
As a rule of thumb, always take your time to decide how to name objects, use smart names, and consider that most common names are probably already taken: remember to check the "List of all members, including inherited members" link in the documentation of the widget type you're using, until you're experienced enough to remember them.
Solutions
The obvious solution is to use a different name for the ui of the dialog:
def createWindow(self):
self.dialog = QDialog()
self.dialog_ui = Ui_Dialog()
self.dialog_ui.setupUi(self.dialog)
self.dialog_ui.anotherLineEdit.setText(self.ui.myLineEdit.text())
self.dialog.show()
A better solution is to create a subclass for your dialog instead:
class MyDialog(QDialog):
def __init__(self, parent=None)
super().__init__(parent)
self.ui = Ui_Dialog()
self.ui.setupUi(self)
class MyWindow(QMainWindow):
# ...
def createWindow(self):
self.dialog = MyDialog()
self.dialog.ui.anotherLineEdit.setText(self.ui.myLineEdit.text())
self.dialog.show()
Also remember that another common (and, to my experience, simpler and more intuitive) method is to use multiple inheritance instead of composition:
class MyDialog(QDialog, Ui_Dialog):
def __init__(self, parent=None)
super().__init__(parent)
self.setupUi(self)
class MyWindow(QMainWindow, Ui_MainWindow):
def __init__(self):
super().__init__()
self.setupUi(self)
self.myLineEdit.setText('some text')
def createWindow(self):
self.dialog = MyDialog()
self.dialog.anotherLineEdit.setText(self.myLineEdit.text())
self.dialog.show()
The only issue of this approach is that it may inadvertently overwrite names of functions of the "main" widget: for instance, if you created a child widget in Designer and renamed it "window". As said above, if you always think thoroughly about the names you assign to objects, this will probably never happen (it doesn't make a lot of sense to name a widget "window").

Maya Python: Button always at the center of the window

I'm starting experimenting with Maya python, and I'm trying to do some UI.
I came across to a really strange problem, I can't get a button to stay in the center of the windows.
I've tried different things but nothing seems to work, here is the code:
import maya.cmds as cmds
cmds.window( width=200 )
WS = mc.workspaceControl("dockName", retain = False, floating = True,mw=80)
submit_widget = cmds.rowLayout(numberOfColumns=1, p=WS)
cmds.button( label='Submit Job',width=130,align='center', p=submit_widget)
cmds.showWindow()
this is a simple version but still, I can't get it to work.
can someone help me?
I honestly don't know the answer as anytime I have to dig into Maya's native UI stuff it makes me question my own life.
So I know it's not exactly what you're asking for, but I'll opt with this: Use PySide instead. At first glance it might make you go "woah, that's way too hard", but it's also a million times better (and actually easier). It's much more powerful, flexible, has great documentation, and also used outside of Maya (so actually useful to learn). Maya's own interface uses the same framework, so you can even edit it with PySide once you're more comfortable with it.
Here's a bare-bones example to create a centered button in a window:
# Import PySide libraries.
from PySide2 import QtCore
from PySide2 import QtWidgets
class MyWindow(QtWidgets.QWidget): # Create a class for our window, which inherits from `QWidget`
def __init__(self, parent=None): # The class's constructor.
super(MyWindow, self).__init__(parent) # Initialize its `QWidget` constructor method.
self.my_button = QtWidgets.QPushButton("My button!") # Create a button!
self.my_layout = QtWidgets.QVBoxLayout() # Create a vertical layout!
self.my_layout.setAlignment(QtCore.Qt.AlignCenter) # Center the horizontal alignment.
self.my_layout.addWidget(self.my_button) # Add the button to the layout.
self.setLayout(self.my_layout) # Make the window use this layout.
self.resize(300, 300) # Resize the window so it's not tiny.
my_window_instance = MyWindow() # Create an instance of our window class.
my_window_instance.show() # Show it!
Not too bad, right?

Using qtDesigner with python seamlessly [duplicate]

This question already has answers here:
QtDesigner changes will be lost after redesign User Interface
(2 answers)
Closed 4 years ago.
I've been looking for a better way to work with frontends made using qtDesigner connected to a python backend. All the methods I have found have the following form:
Make GUI in designer
Output to python code using pyuic (usually with -x option)
Write backend code inside this output file
This methodology is not simple to maintain or edit. Any time you change the UI, it completely breaks workflow: you have to reconvert, generate a new file, fix that file back up to where you were before, then finally get back on track. This requires a lot of manual copy-paste of code, which is an invitation to errors on multiple levels (newly generated file layout may not be the same, manually fixing name changes while pasting, etc.). You can also end up losing work if you aren't careful, since you could accidentally overwrite the file and destroy the backend code.
Also, this doesn't use any of the control in qtDesigner like the Signal/Slot and Action editors. These must be here for something, but I can't find a way to actually direct these to call backend functions.
Is there a better way to work with this, possibly using the features of qtDesigner?
You don't have to add your code in the output file :
If you take a 'home.py' generated by PYUIC, containing a QMainWindow which name set by QtDesigner/generated by Puic would be Ui_Home(), your main code could be :
from home import Ui_Home
from PyQt5.QtGui import *
from PyQt5.QtWidgets import *
from PyQt5.QtCore import *
class window_home(QMainWindow):
def __init__(self, parent=None):
QMainWindow.__init__(self, parent)
#set up the user interface from Designer
self.ui = Ui_Home()
self.ui.setupUi(parent)
#then do anything as if you were in your output file, for example setting an image for a QLabel named "label" (using QtDesigner) at the root QMainWindow :
self.ui.label.setPixmap(QPixmap("./pictures/log.png"))
def Home():
f=QMainWindow()
c=window_home(f)
f.show()
r=qApp.exec_()
if __name__=="__main__":
qApp=QApplication(sys.argv)
Home()
I found an even cleaner method for working with this, that does not require preemptive conversion after each edit at all. Instead it takes the .ui file itself, so all you need to do is restart the program itself to update the design.
import sys
import os
from PyQt5.QtWidgets import QMainWindow, QApplication
from PyQt5 import uic
path = os.path.dirname(__file__) #uic paths from itself, not the active dir, so path needed
qtCreatorFile = "XXXXX.ui" #Ui file name, from QtDesigner, assumes in same folder as this .py
Ui_MainWindow, QtBaseClass = uic.loadUiType(path + qtCreatorFile) #process through pyuic
class MyApp(QMainWindow, Ui_MainWindow): #gui class
def __init__(self):
#The following sets up the gui via Qt
super(MyApp, self).__init__()
self.ui = Ui_MainWindow()
self.ui.setupUi(self)
#set up callbacks
self.ui.NAME OF CONTROL.ACTION.connect(self.test)
def test(self):
#Callback Function
if __name__ == "__main__":
app = QApplication(sys.argv) #instantiate a QtGui (holder for the app)
window = MyApp()
window.show()
sys.exit(app.exec_())
Note that this is Qt5. Qt5 and Qt4 are not API compatible, so it will be a little different in Qt4 (and presumably earlier as well).

How to get text from lineEdit in Pyside?

I'm learning Pyside and I can't seem to get text from a QLineEdit into my own method so that I can input it into a query etc. I know it has to do with lineEdit.text(), but it isn't seeming to work. Do I need to associate it with a signal before the text will go into my variable??
This is the type of thing I've been trying. Do I need a textChanged signal to get it to update or something?? I've tried adding self.line , but that didn't work either, a little rusty on object oriented programming.
line=QtGui.QLineEdit(self)
myVar = line.text()
A short code example would be great. Thanks!
You seem to be creating the object and using it right afterwards. Of course, you get an empty string from text(); it doesn't work like that.
You should add the QLineEdit to a GUI, let the user do something with it and then obtain the text with QLineEdit.text(). To know when exactly the user changed the text, yes, you should connect to the QLineEdit.textEdited slot.
Here is a full example that uses such a mechanism to copy all the text from a QLineEdit to a QLabel as soon as it's modified.
import sys
from PySide.QtCore import *
from PySide.QtGui import *
class MainWindow(QWidget):
def __init__(self):
QWidget.__init__(self)
layout = QVBoxLayout()
self.setLayout(layout)
self.line_edit = QLineEdit()
layout.addWidget(self.line_edit)
self.label = QLabel()
layout.addWidget(self.label)
self.line_edit.textChanged.connect(self.line_edit_text_changed)
self.show()
def line_edit_text_changed(self, text):
self.label.setText(text)
app = QApplication(sys.argv)
mw = MainWindow()
app.exec_()
This is example shows how you can connect your own function to a slot. But since a QLabel has a setText slot, we could just do self.line_edit.textChanged.connect(self.line_edit.setText) and not define a function.
P.S. You really should read some tutorial; I found this one very useful.

How to detect mouse click on images displayed in GUI created using PySide

Firstly, I'm new to Python, Qt and PySide so forgive me if this question seems too simple.
What I'm trying to do is to display a bunch of photos in a grid in a GUI constructed using PySide API. Further, when a user clicks on a photo, I want to be able to display the information corresponding to that photo. Additionally, I would like the container/widget used for displaying the photo to allow for the photo to be changed e.g. I should be able to replace any photo in the grid without causing the entire grid of photos to be created from scratch again.
Initially I tried to use QLabel to display a QPixmap but I realized (whether mistakenly or not) that I have no way to detect mouse clicks on the label. After some searching, I got the impression that I should subclass QLabel (or some other relevant class) and somehow override QWidget's(QLabel's parent class) mousePressEvent() to enable mouse click detection. Problem is I'm not sure how to do that or whether there is any alternative widget I can use to contain my photos other than the QLabel without having to go through subclass customization.
Can anyone suggest a more suitable container other than QLabel to display photos while allowing me to detect mouse clicks on the photo or provide some code snippet for subclassing QLabel to enable it to detect mouse clicks?
Thanks in advance for any replies.
I've added an example of how to emit a signal and connect to another slot. Also the docs are very helpful
from PySide.QtCore import *
from PySide.QtGui import *
import sys
class Main(QWidget):
def __init__(self, parent=None):
super(Main, self).__init__(parent)
layout = QHBoxLayout(self)
picture = PictureLabel("pic.png", self)
picture.pictureClicked.connect(self.anotherSlot)
layout.addWidget(picture)
layout.addWidget(QLabel("click on the picture"))
def anotherSlot(self, passed):
print passed
print "now I'm in Main.anotherSlot"
class PictureLabel(QLabel):
pictureClicked = Signal(str) # can be other types (list, dict, object...)
def __init__(self, image, parent=None):
super(PictureLabel, self).__init__(parent)
self.setPixmap(image)
def mousePressEvent(self, event):
print "from PictureLabel.mousePressEvent"
self.pictureClicked.emit("emit the signal")
a = QApplication([])
m = Main()
m.show()
sys.exit(a.exec_())
Even if the question has been answered, i want to provide an other way that can be used in different situations (see below) :
from PySide.QtCore import *
from PySide.QtGui import *
import sys
class Main(QWidget):
def __init__(self, parent=None):
super(Main, self).__init__(parent)
layout = QHBoxLayout(self)
picture = QLabel()
picture.setPixmap("pic.png")
layout.addWidget(picture)
layout.addWidget(QLabel("click on the picture"))
makeClickable(picture)
QObject.connect(picture, SIGNAL("clicked()"), self.anotherSlot)
def anotherSlot(self):
print("AnotherSlot has been called")
def makeClickable(widget):
def SendClickSignal(widget, evnt):
widget.emit(SIGNAL('clicked()'))
widget.mousePressEvent = lambda evnt: SendClickSignal(widget, evnt)
a = QApplication([])
m = Main()
m.show()
sys.exit(a.exec_())
This way doesn't imply subclassing QLabel so it can be used to add logic to a widget made with QtDeigner.
Pros :
Can be used over QTdesigner compiled files
Can be applied to any kind of widget (you might need to include a super call to the overrided function to ensure widget's normal behavior)
The same logic can be used to send other signals
Cons :
You have to use the QObject syntax to connect signals and slots

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