FAQs about PyQt5

 · 8 mins read

Hi friends, we are going to start a Q and A about PyQt5 here. This page will be dedicated to only Questions that are frequently asked by you and their answers. We will continue to update this page accordingly.

Question:

I found this Traceback (most recent call last): ImportError: cannot import name ‘QtWebEngineWidgets’

Answer:

Highly recommended version is earlier not the latest if you find above trace back ‘QtWebEngineWidgets’. Simply install exactly pip3 install PyQt5==5.15.2

Question:

I can’t find the Qt designer app in windows? I just typed designer in cmd but have this error:

designer : The term 'designer' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the spelling of the name, or if a path was included, verify 
that the path is correct and try again.
At line:1 char:1
+ designer
+ ~~~~~~~~
    + CategoryInfo          : ObjectNotFound: (designer:String) [], CommandNotFoundException
    + FullyQualifiedErrorId : CommandNotFoundException

Answer:

Unfortunatley, in newer versions, the PyQt5 wheels do not provide tools such as Qt Designer that were included in the old binary installers. But the good news is that you can install it via

pip install pyqt5-tools~=5.15

Once installed you can simple type the following to run the Qt designer

pyqt5-tools designer

Question:

I installed PyQt5 via pip and can’t find the “3” folder or the designer executable. How did you install it?

Answer

pip3 install pyqt5
pip3 install pyqt5-tools
After that simply run the command below in Terminal:

qt5-tools designer

Question:

Thank you, these are great tutorials. I do have a problem with getting the main window contents to resize with the main window when I run the app. Can you please tell me what I am doing wrong?

Answer:

Try Python3.6.5 and pip3 install PyQt5==5.15.2

Question:

How did you align the second row of buttons (keyboard shortcut?)

Answer:

Select and Click on Grid layout icon

Question:

Is it possible to store all the new functions in a separately .py-file? I’ve tried this, but afterwards the GUI does not run properly… What can I do, if I want to change something in the Qt-Designer but also to keep my written functions?

Answer:

Hi! You’re welcome and thanks for asking this nice question. Yes there is a way to keep the working gui with functions intact and also upgrade GUI. For this purpose you need

from PyQt5 import uic self.ui = uic.loadUi(‘main.ui’,self) and simply go on use the once created main.py as it is with more functions to add. All you need is open and edit the .ui file and save it without changing it to . py file. You can see the example
here https://pyshine.com/PyQt5-Live-Audio-GUI-with-Start-and-Stop/

Question:

Thank you very much for your video but I have a problem in my project where I use grubCut function for image in label, the problem is exactly when using ‘cv2.setMouseCallback’, we are forced to create an exterior window (cv2.nameWindow) while the modifications must be done directly on the label. Please help me

Answer:

Hi! You’re welcome and thanks for reaching out. Please follow this tutorial where mouse events are used in the image in label https://youtu.be/lGeM3lSdwRM

Question:

Hey, you have done a great job! Can you provide a link to your source code? I’m also building a pyqt5 application and want to use interactive map for timeseries data. Your video inspired me a lot :)

Answer:

Hello! So glad to hear it. You can find the source code in the description under video. https://pyshine.com/Make-GUI-With-Matplotlib-And-PyQt5/

Question:

Hello, this is a great job! This video helped me a lot to do my project! Thank You so much. Can you please plot a csv file data using scatter as well in pyqt5?

Answer:

You’re welcome and thanks for pointing out, we can use plt.scatter function

Question:

Hi, thanks for the continued support! The lessons learned from this videos are very useful. This video shows how to integrate matplotlib into a PyQt5 environment.. Is is possible in addition to integrate matplotplib widgets? Specifically, the RangeSlider widget: from matplotlib.widgets import RangeSlider. I almost got it done using your code as a template, however, the mouse events aren’t passed on to the RangeSlider. Any insights appreciated.

Answer:

Hi, Yes its possible, Multiple Matplotlib widgets can be added in the same way as in the above video. For slider input the widget can be added in a way similar to the video related to Video processing GUI at pyshine.com

Question:

Thanks for this great tutorial. You have done a good job. I have only one problem. When I open a CSV file, it plots alright in the window but it pops out another window titled Figure 1, but it has no plot in it. What can be the problem?

Answer:

Hi! most welcome! Please use Matplotlib version 3.2.1 and Python 3.6.5 . Also which OS you are using? You can install the matplotlib as: pip3 install matplotlib==3.2.1

If your using spyder IDE: then it’s a spyder IDE problem just add plt.ioff() in the code will solve it.

Question:

Nice video, I actually have a problem. After clicking a csv file, I’m not getting the csv file imported, what did I miss, I wrote whole code by watching it

Answer:

Hi! Please copy the code from https://pyshine.com/Make-GUI-With-Matplotlib-And-PyQt5/

Also it is highly recommended to install matplotlib version 3.2.1

Question:

ImportError: cannot import name ‘Qtcore’ from ‘PyQt5’ I am getting this error. I’ve already install pyqt5

Traceback (most recent call last):
  File "C:\Users\Ketan\Desktop\Kedarnath\maingui.py", line 17, in <module>
    from PyQt5 import Qtcore, QtWidgets
ImportError: cannot import name 'Qtcore' from 'PyQt5' (C:\Users\Ketan\AppData\Local\Programs\Python\Python39\lib\site-packages\PyQt5\__init__.py)

Answer:

You are using Python3.9, there might be some issue with it. Try using Python 3.6.5 with PyQt5. pip3 install PyQt5==5.15.2

Question:

How would you keep the internal dimensions the same as a sheet of paper? An A4 sheet is 11.7in x 8.3in. The matplotlib default dpi is 100. How do you make the programs internal (saved image) pixels the same ratio - or exactly 1170px x 830px? Probably not the right forum for this questions, but oh well.

Answer:

Hi, good question. If you want to save figure in terms of pixels, let’s say 800 pixels by 480 pixles then simply change the main window size of the gui. For example: MainWindow.resize(8001000/964, 4801000/817) , 800x480 approximately. In general the Matplotlib figure can be saved in pixels as well:

px = 1/plt.rcParams['figure.dpi']  # pixel in inches
plt.subplots(figsize=(600*px, 200*px))

Question:

Thanks for the video.But when I press on ‘q’ key it does not break the loop.Why is this happening?

Answer:

Most welcome! Good point. The reason its not stopping is because we are using not using cv2.show() to display image. It was added for the debugging purpose. You can add this line cv2.imshow("hello",self.image) before the key = cv2.waitKey(1)&0xFF. Alternatively a flag can be added to break this loop using a stop button

Question:

Without adding this line cv2.imshow(“hello”,self.image) , how can we stop the camera?

Answer:

Hi, please check https://pyshine.com/Video-processing-in-Python-with-OpenCV-and-PyQt5-GUI/ a toggle button is updated and will appear now in the version 2. So you can stop and start using the same button. Thanks for the comments!

Question:

Any thoughts how you could plot csv data coming that comes streaming from a serial port? Basically, get all the ascii up to the carriage-return/line-feed, then parse / plot each csv value, before getting the next line of data. Or do you think the processing would take too long and drop serial data?

Answer:

Hi! serial port data can be plotted by each chunk, depending on the baud rate the stream of chunks can be appended to a csv file. And in a separated thread simple read that csv and plot. In that way the serial data will not drop and can be plotted.

Question:

Hello Sir, how can we plot or scatter plot real-time CSV, txt data files? Can you please help with it?

Answer:

Hi, please follow this https://pyshine.com/How-to-plot-real-time-frame-rate-in-opencv-and-matplotlib/ and instead using plt.plot you can work around with plt.scatter

Question:

Any advise on how we can package this app to an exe?. From my experience packaging apps that make use of libraries such that matplotlib, numpy or pandas make huge executables that makes packaging essentially useless.

Answer:

Yes the package might be large, use pyinstaller

Question:

How to make it possible to change the window and other parameters in real time, while is already playing?

Answer:

Excellent question! Since functions are running under various threads with their own parameters. We can use seprate queue based variables to safely provide the parameter value a thread running a function. In that fuction the parameter value can be applied before the next time step.

Question:

I completely copied your code, but Im getting this error: QObject::killTimer: Timers cannot be stopped from another thread QObject::startTimer: Timers cannot be started from another thread QObject::setParent: Cannot set parent, new parent is in a different thread

Answer:

Hi, Please use this for stopping https://pyshine.com/PyQt5-Live-Audio-GUI-with-Start-and-Stop/