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Date: 2025-07-09 04:59:58
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The issue is here is subtle. The message is informative (not an error), but if you have no idea what is going on it isn't very informative.

matplotlib uses backends to render graphics. Mine uses tkinter by default, which uses the TkAgg backend. Other packages likely do as well.

When you run a python program that uses matplotlib from the command-line it starts a backend but you get no message about interactive mode because you aren't running python interactively.

When you are debugging with an IDE like PyCharm or Visual Studio, python is running in the background as a separate process controlled by the IDE. Since the IDE is controlling python, starting, stopping, inspecting variables, python is running in a kind of interactive mode. The message about backend TkAgg tells you this.

I am running with Visual Studio on windows. If I step my code that uses matplotlib, you don't see the message until you step across "import matplotlib". That is when matplotlib initializes itself and starts the backend.

Interestingly when I just run python from the command-line, which is very clearly interactive, and type

\>>>import matplotlib

\>>>print (f'{matplotlib.get_backend()}')

TkAgg

I don't get the interactive message. Running with an IDE is apparently "more interactive".

Subtle are the ways of matplotlib and backends.

======

For those of you who are curious, on my machine there is a folder of 29 matplotlib backends. It is

C:\Python38\Lib\site-packages\matplotlib\backends

The message itself comes from Visual Studio code that loads the matplotlib backend not the backend itself. If you search your python and IDE files you can likely find the code. In my installation it is called matplotlibtools.py in a Visual Studio folder.

It gives some hints about matplotlib backend loading. Look for

"is interactive backend. Turning interactive mode on"

In the function

def activate_matplotlib(enable_gui_function):

the message is controlled by

matplotlib.is_interactive()

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Posted by: NemoX