[Python] UserWarning: FigureCanvasAgg is non-interactive, and thus cannot be shown

I am trying to show a matplotlib.pyplot figure on Python 3.10 but can't. I am aware of this question and tried their answers but is still unsuccessful. The default OS distribution is Ubuntu 24.04 using Python 3.12 as a default.

Here is how I setup the Python 3.10 project venv and installed numpy and matplotlib:

$ uv init test_py310 --python 3.10
Initialized project `test-py310` at `/home/user/test_py310`
$ cd test_py310/
$ uv add numpy matplotlib
Using CPython 3.10.16
Creating virtual environment at: .venv
Resolved 12 packages in 136ms
Prepared 1 package in 1.96s
Installed 11 packages in 43ms
+ contourpy==1.3.2
+ cycler==0.12.1
+ fonttools==4.57.0
+ kiwisolver==1.4.8
+ matplotlib==3.10.1
+ numpy==2.2.5
+ packaging==25.0
+ pillow==11.2.1
+ pyparsing==3.2.3
+ python-dateutil==2.9.0.post0
+ six==1.17.0


test_matplotlib.py:

import numpy as np
import matplotlib.pyplot as plt

x = np.linspace(0, 10, 100)
y = np.sin(x)
plt.plot(x, y, label='sin(x)', color='blue', linestyle='--')
plt.show()


Error:

/home/user/Coding/test_py310/.venv/bin/python /home/user/test_py310/test_matplotlib,py
/home/user/test_py310/test_matplotlib,py:7: UserWarning: FigureCanvasAgg is non-interactive, and thus cannot be shown
plt.show()


Next, I tried installing PyQt5 as shared by this answer but still encountered error.

$ uv add pyqt5
Resolved 15 packages in 89ms
Installed 3 packages in 45ms
+ pyqt5==5.15.11
+ pyqt5-qt5==5.15.16
+ pyqt5-sip==12.17.0


Running the same python script

$ /home/user/test_py310/.venv/bin/python /home/user/test_py310/test_matplotlib,py
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Available platform plugins are: eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, webgl, xcb.

Aborted (core dumped)


Changing import matplotlib.pyplot as plt to:

import matplotlib
matplotlib.use('TkAgg')
import matplotlib.pyplot as plt


Gave this error:

$ /home/user/test_py310/.venv/bin/python /home/user/test_py310/test_matplotlib,py
AttributeError: module '_tkinter' has no attribute '__file__'. Did you mean: '__name__'?

The above exception was the direct cause of the following exception:

ImportError: failed to load tkinter functions

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
File "/home/user/test_py310/test_matplotlib,py", line 9, in <module>
plt.plot(x, y, label='sin(x)', color='blue', linestyle='--')
File "/home/user/test_py310/.venv/lib/python3.10/site-packages/matplotlib/pyplot.py", line 3827, in plot
return gca().plot(
File "/home/user/test_py310/.venv/lib/python3.10/site-packages/matplotlib/pyplot.py", line 2774, in gca
return gcf().gca()
File "/home/user/test_py310/.venv/lib/python3.10/site-packages/matplotlib/pyplot.py", line 1108, in gcf
return figure()
File "/home/user/test_py310/.venv/lib/python3.10/site-packages/matplotlib/pyplot.py", line 1042, in figure
manager = new_figure_manager(
File "/home/user/test_py310/.venv/lib/python3.10/site-packages/matplotlib/pyplot.py", line 551, in new_figure_manager
_warn_if_gui_out_of_main_thread()
File "/home/user/test_py310/.venv/lib/python3.10/site-packages/matplotlib/pyplot.py", line 528, in _warn_if_gui_out_of_main_thread
canvas_class = cast(type[FigureCanvasBase], _get_backend_mod().FigureCanvas)
File "/home/user/test_py310/.venv/lib/python3.10/site-packages/matplotlib/pyplot.py", line 369, in _get_backend_mod
switch_backend(rcParams._get("backend"))
File "/home/user/test_py310/.venv/lib/python3.10/site-packages/matplotlib/pyplot.py", line 425, in switch_backend
module = backend_registry.load_backend_module(newbackend)
File "/home/user/test_py310/.venv/lib/python3.10/site-packages/matplotlib/backends/registry.py", line 317, in load_backend_module
return importlib.import_module(module_name)
File "/home/user/.local/share/uv/python/cpython-3.10.16-linux-x86_64-gnu/lib/python3.10/importlib/__init__.py", line 126, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File "<frozen importlib._bootstrap>", line 1050, in _gcd_import
File "<frozen importlib._bootstrap>", line 1027, in _find_and_load
File "<frozen importlib._bootstrap>", line 1006, in _find_and_load_unlocked
File "<frozen importlib._bootstrap>", line 688, in _load_unlocked
File "<frozen importlib._bootstrap_external>", line 883, in exec_module
File "<frozen importlib._bootstrap>", line 241, in _call_with_frames_removed
File "/home/user/test_py310/.venv/lib/python3.10/site-packages/matplotlib/backends/backend_tkagg.py", line 1, in <module>
from . import _backend_tk
File "/home/user/test_py310/.venv/lib/python3.10/site-packages/matplotlib/backends/_backend_tk.py", line 25, in <module>
from . import _tkagg
ImportError: initialization failed


Using

import matplotlib
matplotlib.use('Qt5Agg')
import matplotlib.pyplot as plt


gave

$ /home/user/test_py310/.venv/bin/python /home/user/test_py310/test_matplotlib,py
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Available platform plugins are: eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, webgl, xcb.

Aborted (core dumped)


I have also removed pyqt5 and added pyqt6, and used matplotlib.use('Qt6Agg') but got this error:

$ /home/user/test_py310/.venv/bin/python /home/user/test_py310/test_matplotlib,py
Traceback (most recent call last):
File "/home/user/test_py310/test_matplotlib,py", line 4, in <module>
matplotlib.use('Qt6Agg')
File "/home/user/test_py310/.venv/lib/python3.10/site-packages/matplotlib/__init__.py", line 1265, in use
name = rcsetup.validate_backend(backend)
File "/home/user/test_py310/.venv/lib/python3.10/site-packages/matplotlib/rcsetup.py", line 278, in validate_backend
raise ValueError(msg)
ValueError: 'Qt6Agg' is not a valid value for backend; supported values are ['gtk3agg', 'gtk3cairo', 'gtk4agg', 'gtk4cairo', 'macosx', 'nbagg', 'notebook', 'qtagg', 'qtcairo', 'qt5agg', 'qt5cairo', 'tkagg', 'tkcairo', 'webagg', 'wx', 'wxagg', 'wxcairo', 'agg', 'cairo', 'pdf', 'pgf', 'ps', 'svg', 'template']


What must I do to be able to plot a matplotlib.pyplot figure in a virtual environment that is installed with Python 3.10?

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