what is sys.argv used for in python PyQt4

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I'm still a beginner when it comes to programming, and I'm especially new when it comes GUI programming. I'm using python with PyQt4 and im following a tutorial guide. The following code block is relatively easy to follow:

import sys
from PyQt4 import QtGui
def window():
    app = QtGui.QApplication(sys.argv)
    w = QtGui.QWidget()
    b= QtGui.QLabel(w)
    b.setText("Hello World!")
    w.setGeometry(100,100,200,50)
    b.move(50,20)
    w.setWindowTitle("PyQt")
    w.show()
    sys.exit(app.exec_())
if __name__ == '__main__':
    window()

I can follow whats going on here quite well, but could someone explain to me what the sys.argv is actually doing? I don't want to just blindly put this in every time in the hope that it will make my code work!

PyQT Basic Tutorial, We are creating a QApplication object, and saving it to "app." Here, we pass this sys.argv argument because sys.argv allows us to pass command line arguments � sys.argv() is an array for command line arguments in Python. To employ this module named “sys” is used. sys.argv is similar to an array and the values are also retrieved like Python array. The sys module. The sys module provides functions and variables used to manipulate different parts of the Python runtime environment.

You don't need to use sys.argv in a PyQt application.

It's only really useful if you want to use command-line arguments. If you don't, you can just pass in an empty list:

app = QtGui.QApplication([])

When you do use sys.argv, the first argument is automatically set to the script name, and Qt will use this to set the applicationName(). The list of arguments can be accessed later via the arguments() method:

# test.py
import sys
from PyQt4 import QtGui

app = QtGui.QApplication(sys.argv)

print('ARGS: %s' % app.arguments())
print('NAME: %r' % app.applicationName())

Output:

$ python test.py -f foo
ARGS: ['test.py', '-f', 'foo']
NAME: 'test.py'

But note that some pre-defined arguments are handled internally by Qt, and will be automatically removed from the arguments:

$ python test.py -f foo -stylesheet=style.qss
ARGS: ['test.py', '-f', 'foo']
NAME: 'test.py'

python, Because this call invokes an underlying C++ function which uses argv and doesn 't know about python. Qt understand a set of command line� What is sys.argv? sys.argv is a list in Python, which contains the command-line arguments passed to the script. With the len(sys.argv) function you can count the number of arguments. If you are gonna work with command line arguments, you probably want to use sys.argv. To use sys.argv, you will first have to import the sys […]

sys.argv is not PyQt4 specific. It contains all the command line arguments that were used to start the program in the form of a list.

For example when you start ./test.py arg1 arg2 sys.argv would contain:

sys.argv[0] == "./test.py"
sys.argv[1] == "arg1"
sys.argv[2] == "arg2"

And with this you could count the number of arguments, this will include the name of the program itself as shown above:

len(sys.argv) 

First programs in PyQt4, The following classes are used: QtCore. #!/usr/bin/python """ ZetCode PyQt4 tutorial In this example, we create a simple window in PyQt4. author: Jan The sys.argv parameter is a list of arguments from the command line. app = QtGui.QApplication(sys.argv) We are creating a QApplication object, and saving it to "app." Here, we pass this sys.argv argument because sys.argv allows us to pass command line arguments to the application. For more information on this, see our sys module with Python tutorial. window = QtGui.QWidget() Next, we define our window.

sys.argv contains all the command-line arguments that were passed to the program when it was launched. The constructor of QApplication needs these launch options in some circumstances, such as debugging.

pyqt, PyQt is a Python binding to the popular cross-platform Qt application framework commonly used to make graphical applications. PyQt4 supports setStatusBar( status_bar) if __name__ == '__main__': app = App(sys.argv) sys.exit(app.exec_() )� PyQt GUI Programming Tutorial. PyQt is a module to make desktop software with Python. This works on all desktop systems including Mac OS X, Windows and Linux. If you want to make desktop apps with Python, PyQt is the module you need to make them. After creating your app, you can create an installation program with fbs.

QApplication can optionally accept additional command line arguments, say you have a PyQT or PySide program with CheckBox and Slider, and you run it with the following command:

$ python3 checkbox_slider.py -style fusion  

you'll find the style is different, that mean sys.argv has its practical use in some cases. see more argument options from official website

PopUp Alert in Lines - PyQt Programming, Python puts the words it is actually given in the sys.argv list.) Now we When a widget is used like this, PyQt automatically gives it a title bar. 6 import sys 7 from PyQt4.QtGui import QApplication, QWidget 8 9 # Every PyQt4 application must create an application object. 10 # The application object is located in the QtGui module. 11 app = QApplication (sys. argv) 12 13 # The QWidget widget is the base class of all user interface objects in PyQt4. 14 # We provide the default constructor for QWidget.

PyQt Tutorial: Python GUI Designer, PyQt is a Python binding of the cross-platform GUI toolkit Qt, implemented as a In this tutorial, PyQt5 will be used for the demonstration of examples. sys.argv is the list of command-line parameters that you can pass to the� PyQt is a python binding of the open-source widget-toolkit Qt, which also functions as a cross-platform application development framework. Qt is a popular C++ framework for writing GUI applications for all major desktop, mobile, and embedded platforms (supports Linux, Windows, MacOS, Android, iOS, Raspberry Pi, and more).

Command line arguments, Sys argv. You can get access to the command line parameters using the sys module. len(sys.argv) Docopt can be used to create command line interfaces. libraries. It was originally developed to create PyQt, the Python bindings for the Qttoolkit, but can be used to create bindings for any C or C++ library. For example, it is also used to create wxPython, the Python bindings for the

How to use sys.argv in Python, If your making a python script and want more features for passing command line arguments take a look at the argparse library. I have used it quite� Various learning resources – because PyQt is one of the most used UI frameworks for Python, you can get easy access to a wide array of documentation. Easy to master – PyQt comes with a user-friendly, straightforward API functionality, along with specific classes linked to Qt C++.

Comments
  • Thank you. After reading jbm's answer full of info, this practical example makes a lot of sense. Thanks guys!
  • Any chance you could give an example of what kind of command-line argument would be passed to the program? I'm trying to understand what kind of information this relates to
  • @KierranPurden Take a look at the Qt documentation about QApplication
  • @KierranPurden For example, -style x will force the application to use style x that run. There's plenty of others in that article that are useful for debugging.
  • @KierranPurden: Say, you write a text editor in Qt. Then the usual command line argument may be the name of the edited file. This is only an example. It fully depends on what you need to pass through the command line arguments. But for that you can read sys.argv directly. More important is that there is a convention for a window applications (in Unix-based systems) for how to pass the initial dimensions of the main window, for example. And this is what Qt tries to get on its own -- independently on what you want to solve.