Broken print output -- prepended by garbage

[dain-xyz]

I installed Jupyter and Ipython in a virtual environment. Whenever I type something in the IPython REPL and press enter, the output is prepended with a bunch of repeated garbage:

In [2]: print("Hello, world!")

line='print("Hello, world!")\n', last_line=b'', encoding=None
print
(
"Hello, world!"
)


line=b'', last_line='print("Hello, world!")\n', encoding=None

line='print("Hello, world!")\n', last_line=b'', encoding=None
print
(
"Hello, world!"
)


line=b'', last_line='print("Hello, world!")\n', encoding=None

line='print("Hello, world!")\n', last_line=b'', encoding=None
print
(
"Hello, world!"
)


line=b'', last_line='print("Hello, world!")\n', encoding=None
Hello, world!

In [3]: 2 + 2

line='2 + 2\n', last_line=b'', encoding=None
2
+
2


line=b'', last_line='2 + 2\n', encoding=None

line='2 + 2\n', last_line=b'', encoding=None
2
+
2


line=b'', last_line='2 + 2\n', encoding=None

line='2 + 2\n', last_line=b'', encoding=None
2
+
2


line=b'', last_line='2 + 2\n', encoding=None

line='2 + 2', last_line=b'', encoding=None
2
+
2
line='', last_line='2 + 2', encoding=None
Out[3]: 4

This garbage output occurs in both IPython REPL in a terminal, and Jupyter notebooks in a browser.

I'm running Windows 10 with Python 3.8.1. The package versions are:

• jupyter 1.0.0
• ipython 7.17.0
• notebook 6.1.1

These were installed via Poetry. I installed the exact same Python and package versions on a separate PC (running Linux) and the problem did not appear. Is this a bug with IPython, or is something configured wrong on my Windows PC?

[Carreau]

probably a debug statement forgotten somewhere, good to know you are on windows.
Does it do the same if you install IPython 7.16.0 ?
If you get an earlier version of prompt_toolkit ?
If you get an earlier version of jedi ?

[dain-xyz]

I downgraded my Python version back to 3.7.6, changing nothing else, and the problem went away, so it seems to be caused by something that changed between 3.7 and 3.8.

The full list of packages in the two environments:

backcall 0.2.0
colorama 0.4.3
decorator 4.4.2
ipython 7.17.0
ipython-genutils 0.2.0
jedi 0.17.2
parso 0.7.1
pickleshare 0.7.5
prompt-toolkit 3.0.6
pygments 2.6.1
six 1.15.0
traitlets 4.3.3
wcwidth 0.2.5

[dain-xyz]

I upgraded to Python 3.8.6, that seems to have fixed it.