No longer works for output in Jupyter

[mcrutch]

• Version 2.0.1 worked with Jupyter/JupyterLab
• Version 2.1.0 does not.

Pretty sure the _can_do_color function is the culprit. While it might not have been intentional that it worked in Jupyter, it did.

termcolor/src/termcolor/termcolor.py

Line 106 in ec269e6

def _can_do_colour() -> bool:

[hugovk]

Please can you give more info?

A minimal reproducible example would help:

https://stackoverflow.com/help/minimal-reproducible-example

What did you do?

What did you expect?

What actually happened?

[mcrutch]

• Run Jupyter Notebook or Jupyter Lab
• Create a new notebook
• Execute this cell

!pip install termcolor==2.0.1
from termcolor import colored
print(colored("Hello World","red"))

Result: Prints Hello World in red in the output cell

• Restart kernel
• update cell and execute

!pip install termcolor==2.1.0
from termcolor import colored
print(colored("Hello World","red"))

Results: Prints Hello World in theme default color

[hugovk]

Thank you!

Please can you let me know the value of each of the conditions in _can_do_colour?

print("ANSI_COLORS_DISABLED" in os.environ)
print("NO_COLOR" in os.environ)
print("FORCE_COLOR" in os.environ)
print(hasattr(sys.stdout, "isatty"))
print(hasattr(sys.stdout, "isatty") and sys.stdout.isatty())
print(os.environ.get("TERM") != "dumb")

[mcrutch]

False
False
False
True
False
True

Possibly of value, sys.stdout is a ipykernel.iostream.OutStream

[hugovk]

Thanks, so the problem is Jupyter is returning False for sys.isatty, despite being interactive.

Looks like they were going to set it to return True, but instead decided to default it to True and make it configurable to avoid problems with things like pagers:

ipython/ipykernel#683

I'll dig a bit more, the short term workaround is to set an env var FORCE_COLOR=1, or configure ipykernel.iostream.OutStream so isatty=True.

[hugovk]

I asked over at ipython/ipykernel#1024.

[hugovk]

@mcrutch Please can you retest with IPython Kernel for Jupyter v6.18.0? This should now be fixed.

• Recommended way to detect interactive terminal? ipython/ipykernel#1024
• Add terminal color support ipython/ipykernel#1025

[realtimeprojects]

A simple example how to reproduce this problem with the tee command:

python3 -m termcolor | tee test.log

[hugovk]

@realtimeprojects This issue is for Jupyter. If you're piping the output then we have no idea if the receiving program can accept the colour codes, that's why we're doing tty detection. If you want to force it, please use the env var:

FORCE_COLOR=1 python3 -m termcolor | tee test.log

[realtimeprojects]

@hugovk:

I was just commenting on this issue because I think this is a generic problem and not specific to Jupyter. Sorry for that!

I think it is a bad idea to check the sys.stdout for "isatty()" since you don't know where your colorized message will go to. It is not guaruanteed that it will be streamed to sys.stdout (or sys.stderr). This is very application specific. And even if the output stream is not a tty it might still support colorization, what I assume is the case for Jupyter or any integrated environment simulating a terminal.

I use termcolor for colorizing "python logging" messages, which go to sys.stderr and if I run my app and redirect stdout to a file, the logging messages are not colorized as well.

This check also fails when used in azure devops pipelines.

Furthermore, I consider the "isatty" check as rather "expensive" when done for each single message and you have a lot of log messages to colorize.

[hugovk]

Closing this issue as fixed in Jupyter: #28 (comment)

---

@realtimeprojects Thank you for the feedback.

Can you use the FORCE_COLOR=1 env var?

I'm considering adding a no_color parameter (#2 (comment)), would a force_color parameter help?

This check also fails when used in azure devops pipelines.

Yes, I guess this is like GitHub Actions: actions/runner#241

I recommend adding FORCE_COLOR=1 as an env var to your workflow (or similar), this will help for other tools as well:

• https://cs.github.com/?scopeName=All+repos&scope=&q=path%3A.github%2Fworkflows%2F*.yml+FORCE_COLOR

[hugovk]

Please see PR #38 to add parameters to override the environment variables.