th 188 - Migrate From PyQt4 to PyQt5: Step-by-Step Guide

Migrate From PyQt4 to PyQt5: Step-by-Step Guide

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th?q=Pyqt4 To Pyqt5 How? - Migrate From PyQt4 to PyQt5: Step-by-Step Guide

If you are a developer who is using PyQt4 for your projects, it is crucial to migrate to PyQt5. The latest version of PyQt comes with updated features and enhancements that make it more flexible and user-friendly. Migrating from PyQt4 to PyQt5 can seem like an overwhelming task, but with the right steps and guidance, you can smoothly transition to the new version.

The good news is, we have created a step-by-step guide to help you navigate this process. Our guide covers all aspects of the migration, including installing the latest version, updating any deprecated components, and making necessary code changes.

We understand that transitioning to a new version can be daunting, and it might take some time. However, by the end of our guide, you will have a better understanding of how to use PyQt5 effectively and efficiently.

So, if you are ready to take your PyQt skills to the next level, we invite you to read our comprehensive article on how to migrate from PyQt4 to PyQt5. Trust us; it will be worth your time and effort!

th?q=Pyqt4%20To%20Pyqt5%20How%3F - Migrate From PyQt4 to PyQt5: Step-by-Step Guide
“Pyqt4 To Pyqt5 How?” ~ bbaz


PyQt5 is a powerful tool for creating graphical user interfaces (GUI) in Python. It comes with numerous new features and improvements compared to its predecessor, PyQt4. In this article, we will discuss the step-by-step guide for migrating from PyQt4 to PyQt5.

Key differences between PyQt4 and PyQt5

Before we delve into the migration process, it’s important to understand the key differences between PyQt4 and PyQt5. The following table outlines some of the critical differences:

Feature PyQt4 PyQt5
Naming conventions Old style (e.g., QtGui, QtCore) New style (e.g., QtWidgets, QtCore)
Event loop handling Qt main loop and Python interpreter run in separate threads The Qt main loop replaces the Python interpreter loop
API changes Major breaking changes to the API Mostly backward-compatible with PyQt4
Python version support Supports up to Python 3.3 Supports versions up to Python 3.9

Preparing for migration

To migrate from PyQt4 to PyQt5, you should first ensure that you have the latest version of PyQt5 installed. You can do so using the pip command:

pip install pyqt5

Once you have the latest version installed, you will also need to check all the third-party dependencies that you are using in your PyQt4 project. Some of these may no longer be compatible with PyQt5, necessitating changes to your code or finding alternative packages.

Updating your import statements

The first task is to update all the import statements in your code. As mentioned earlier, PyQt5 uses a new naming convention for its modules (e.g., QtWidgets, QtCore) compared to PyQt4. Therefore, you need to update all the imports in your code accordingly. For example:

Old: from PyQt4.QtGui import QPushButton

New: from PyQt5.QtWidgets import QPushButton

You should go through your entire codebase and make these changes to all import statements.

Changes to signals and slots

One of the significant differences between PyQt4 and PyQt5 is how signals and slots work. In PyQt4, you could define signals explicitly as class attributes. However, this approach is no longer supported in PyQt5. Instead, you can use the new-style signal syntax to define signals. Here’s an example:

PyQt4: self.buttonClicked = QtCore.pyqtSignal()

PyQt5: buttonClicked = QtCore.pyqtSignal()

You need to update all the signal definitions in your codebase accordingly.

Event loop handling changes

Another significant difference between PyQt4 and PyQt5 is how the event loop is handled. In PyQt4, the main application loop and the Python interpreter run in separate threads. However, in PyQt5, the Qt main loop replaces the Python interpreter loop. Therefore, you need to be mindful of this when updating your code. The following is an example of how you can update your event loop handling function in PyQt5:

PyQt4: QtCore.QObject.connect(, QtCore.SIGNAL(‘lastWindowClosed()’), self.quit)


Note the use of different syntax in the two versions for setting up the slot.

Changes to API

PyQt5 includes several changes to its API from PyQt4. Most of these changes are backward compatible, meaning that your code should generally still work. However, some of the significant changes to the API may require modification to your code. For example, one such change is the QWidget::setAutoFillBackground() method, which no longer exists in PyQt5. Instead, you can use QWidget::setBackgroundRole(). Therefore, when migrating, ensure that you’re using the latest PyQt5 API.

UI file changes

If you’re using the popular PyQt designer tool (Qt Designer) to create user interfaces, note that there are significant differences in how PyQt4 and PyQt5 handle UI files. PyQt5 uses a newer version of the Qt User Interface Compiler (UIC), which requires an extended syntax. Therefore, you likely need to update your PyQt4 UI files before importing them into PyQt5.

Testing and debugging

Once you’ve gone through all the steps outlined above, it’s essential to test and debug your code thoroughly. You should run thorough functional tests to ensure that all your features work as expected. Additionally, you should also conduct unit tests to ensure that your codebase is stable and bug-free.


In conclusion, migrating from PyQt4 to PyQt5 is a significant undertaking. However, it’s inevitable, as PyQt4 will no longer be supported. Therefore, it’s best to get ahead of the curve and migrate your codebase. The above-listed steps should guide you through the migration process, and once complete, you can enjoy the numerous benefits of using PyQt5 for your GUIs.

Dear blog visitors,

Thank you for taking the time to read our article on migrating from PyQt4 to PyQt5. We understand that change can sometimes be intimidating, but we hope that our step-by-step guide has provided a clear and concise roadmap for making the transition.

If you have any questions or concerns about the migration process, feel free to leave a comment on this post or send us an email. We are always here to help and support you as you make the switch to the newer version of PyQt.

We hope that you have found this article informative and useful. We believe that PyQt5 offers significant improvements over its predecessor, and we encourage you to take advantage of the new features and capabilities it provides. Thank you again for visiting our blog, and we look forward to hearing from you soon.

People also ask about migrating from PyQt4 to PyQt5:

  • What is PyQt?
  • What are the differences between PyQt4 and PyQt5?
  • Why should I migrate from PyQt4 to PyQt5?
  • Is the migration process difficult?
  • What are the steps involved in migrating from PyQt4 to PyQt5?
  • Are there any compatibility issues that I need to be aware of?


  1. PyQt is a set of Python bindings for the Qt application framework. It provides the necessary tools to create graphical user interfaces (GUI) in Python.
  2. PyQt5 is the latest version of PyQt, which has several new features and improvements compared to PyQt4. These include improved performance, better support for modern GUI technologies, and enhanced compatibility with other platforms.
  3. Migrating from PyQt4 to PyQt5 is recommended for developers who want to take advantage of the latest features and enhancements provided by PyQt5.
  4. The migration process may require some effort, but it is not overly difficult. The steps involved are straightforward and can be easily accomplished by most developers.
  5. The steps involved in migrating from PyQt4 to PyQt5 include updating your code to use the latest API, replacing deprecated functions and classes, and testing your application to ensure compatibility with PyQt5.
  6. While there may be some compatibility issues that need to be addressed during the migration process, these are generally minor and can be resolved with minimal effort.