Debugger crashes when importing matplotlib with justMyCode set to false

[noamgot]

Environment data

• Python Debugger version: 2025.6.0
• debugpy version: 1.8.13
• OS and version: Window 11, connected with SSH to Ubuntu 22.04.3 LTS (the code runs on the Linux machine)
• Environment: pixi (conda) environment with python 3.10
• IDE: Cursur v.1.2.4 (VSCode 1.99.3)

Actual behavior

When trying to debug a code that imports matplotlib with justMyCode set to false (in my user settings), I get this error:

Traceback (most recent call last):
  File "_pydevd_bundle\\pydevd_cython.pyx", line 1090, in _pydevd_bundle.pydevd_cython.PyDBFrame.trace_dispatch
  File "_pydevd_bundle\\pydevd_cython.pyx", line 494, in _pydevd_bundle.pydevd_cython.PyDBFrame.do_wait_suspend
  File "$USER/.cursor-server/extensions/ms-python.debugpy-2025.6.0-linux-x64/bundled/libs/debugpy/_vendored/pydevd/pydevd.py", line 2188, in do_wait_suspend
    keep_suspended = self._do_wait_suspend(thread, frame, event, arg, trace_suspend_type, from_this_thread, frames_tracker)
  File "$USER/.cursor-server/extensions/ms-python.debugpy-2025.6.0-linux-x64/bundled/libs/debugpy/_vendored/pydevd/pydevd.py", line 2214, in _do_wait_suspend
    self._activate_gui_if_needed()
  File "$USER/.cursor-server/extensions/ms-python.debugpy-2025.6.0-linux-x64/bundled/libs/debugpy/_vendored/pydevd/pydevd.py", line 1676, in _activate_gui_if_needed
    activate_function()
  File "$USER/.cursor-server/extensions/ms-python.debugpy-2025.6.0-linux-x64/bundled/libs/debugpy/_vendored/pydevd/pydevd.py", line 1659, in <lambda>
    "matplotlib": lambda: activate_matplotlib(do_enable_gui),
  File "$USER/.cursor-server/extensions/ms-python.debugpy-2025.6.0-linux-x64/bundled/libs/debugpy/_vendored/pydevd/pydev_ipython/matplotlibtools.py", line 138, in activate_matplotlib
    gui, backend = find_gui_and_backend()
  File "$USER/.cursor-server/extensions/ms-python.debugpy-2025.6.0-linux-x64/bundled/libs/debugpy/_vendored/pydevd/pydev_ipython/matplotlibtools.py", line 64, in find_gui_and_backend
    backend = matplotlib.rcParams["backend"]
AttributeError: partially initialized module 'matplotlib' has no attribute 'rcParams' (most likely due to a circular import)
Traceback (most recent call last):
  File "$USER/project/.pixi/envs/default/lib/python3.10/runpy.py", line 196, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "$USER/project/.pixi/envs/default/lib/python3.10/runpy.py", line 86, in _run_code
    exec(code, run_globals)
  File "$USER/.cursor-server/extensions/ms-python.debugpy-2025.6.0-linux-x64/bundled/libs/debugpy/adapter/../../debugpy/launcher/../../debugpy/__main__.py", line 71, in <module>
    cli.main()
  File "$USER/.cursor-server/extensions/ms-python.debugpy-2025.6.0-linux-x64/bundled/libs/debugpy/adapter/../../debugpy/launcher/../../debugpy/../debugpy/server/cli.py", line 501, in main
    run()
  File "$USER/.cursor-server/extensions/ms-python.debugpy-2025.6.0-linux-x64/bundled/libs/debugpy/adapter/../../debugpy/launcher/../../debugpy/../debugpy/server/cli.py", line 351, in run_file
    runpy.run_path(target, run_name="__main__")
  File "$USER/.cursor-server/extensions/ms-python.debugpy-2025.6.0-linux-x64/bundled/libs/debugpy/_vendored/pydevd/_pydevd_bundle/pydevd_runpy.py", line 310, in run_path
    return _run_module_code(code, init_globals, run_name, pkg_name=pkg_name, script_name=fname)
  File "$USER/.cursor-server/extensions/ms-python.debugpy-2025.6.0-linux-x64/bundled/libs/debugpy/_vendored/pydevd/_pydevd_bundle/pydevd_runpy.py", line 127, in _run_module_code
    _run_code(code, mod_globals, init_globals, mod_name, mod_spec, pkg_name, script_name)
  File "$USER/.cursor-server/extensions/ms-python.debugpy-2025.6.0-linux-x64/bundled/libs/debugpy/_vendored/pydevd/_pydevd_bundle/pydevd_runpy.py", line 118, in _run_code
    exec(code, run_globals)
  File "$USER/.cursor-server/data/User/globalStorage/buenon.scratchpads/scratchpads/587806bd8d2d5e49dde1948c853676a7/scratch9.py", line 1, in <module>
    import matplotlib.pyplot as plt
  File "$USER/project/.pixi/envs/default/lib/python3.10/site-packages/matplotlib/__init__.py", line 1, in <module>
    """
  File "$USER/project/.pixi/envs/default/lib/python3.10/site-packages/matplotlib/__init__.py", line 1, in <module>
    """
  File "_pydevd_bundle\\pydevd_cython.pyx", line 1697, in _pydevd_bundle.pydevd_cython.SafeCallWrapper.__call__
  File "_pydevd_bundle\\pydevd_cython.pyx", line 634, in _pydevd_bundle.pydevd_cython.PyDBFrame.trace_dispatch
  File "_pydevd_bundle\\pydevd_cython.pyx", line 1112, in _pydevd_bundle.pydevd_cython.PyDBFrame.trace_dispatch
  File "_pydevd_bundle\\pydevd_cython.pyx", line 1090, in _pydevd_bundle.pydevd_cython.PyDBFrame.trace_dispatch
  File "_pydevd_bundle\\pydevd_cython.pyx", line 494, in _pydevd_bundle.pydevd_cython.PyDBFrame.do_wait_suspend
  File "$USER/.cursor-server/extensions/ms-python.debugpy-2025.6.0-linux-x64/bundled/libs/debugpy/_vendored/pydevd/pydevd.py", line 2188, in do_wait_suspend
    keep_suspended = self._do_wait_suspend(thread, frame, event, arg, trace_suspend_type, from_this_thread, frames_tracker)
  File "$USER/.cursor-server/extensions/ms-python.debugpy-2025.6.0-linux-x64/bundled/libs/debugpy/_vendored/pydevd/pydevd.py", line 2214, in _do_wait_suspend
    self._activate_gui_if_needed()
  File "$USER/.cursor-server/extensions/ms-python.debugpy-2025.6.0-linux-x64/bundled/libs/debugpy/_vendored/pydevd/pydevd.py", line 1676, in _activate_gui_if_needed
    activate_function()
  File "$USER/.cursor-server/extensions/ms-python.debugpy-2025.6.0-linux-x64/bundled/libs/debugpy/_vendored/pydevd/pydevd.py", line 1659, in <lambda>
    "matplotlib": lambda: activate_matplotlib(do_enable_gui),
  File "$USER/.cursor-server/extensions/ms-python.debugpy-2025.6.0-linux-x64/bundled/libs/debugpy/_vendored/pydevd/pydev_ipython/matplotlibtools.py", line 138, in activate_matplotlib
    gui, backend = find_gui_and_backend()
  File "$USER/.cursor-server/extensions/ms-python.debugpy-2025.6.0-linux-x64/bundled/libs/debugpy/_vendored/pydevd/pydev_ipython/matplotlibtools.py", line 64, in find_gui_and_backend
    backend = matplotlib.rcParams["backend"]
AttributeError: partially initialized module 'matplotlib' has no attribute 'rcParams' (most likely due to a circular import)

Re-setting justMyCode to true allows me to debug (but without stepping into other libraries' code, as I wish to do in many times)

Expected behavior

I wish I could avoid this error 😄

Steps to reproduce:

1. make sure that justMyCode set to false (e.g, in the user settings)
2. run this example code I simply pressed the small debugging icon at the top right (Python Debugger: Debug python file):

import matplotlib.pyplot as plt
import numpy as np

# Generate some data
x = np.linspace(0, 2 * np.pi, 100)
y = np.sin(x)

# Create the plot
plt.plot(x, y, label='sin(x)')
plt.title('Simple Sine Wave')
plt.xlabel('x')
plt.ylabel('sin(x)')
plt.legend()
plt.grid(True)
plt.show()

thanks!

[eleanorjboyd]

will investigate- thanks