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When I am developing python code I often have a repl open alongside of it running snippets ofcode as I go. Ipython is my repl of choice, and I hace tricked it out the best I can and I really like it. The problem I recently discovered is that I have way overcomplicated it.

What Have I done??

So in the past the way I have setup a few extensions for myself is to add something like this to my ~/.ipython/profile_default/startup directory. It sets up some things like rich highlighting or in this example automatic imports. I even went as far as installing some of these in the case I didn't have them installed.


import subprocess

from IPython import get_ipython
from IPython.core.error import UsageError

ipython = get_ipython()

try:
    ipython.run_line_magic("load_ext pyflyby", "inline")
except UsageError:
    print("installing pyflyby")
    subprocess.Popen(
        ["pip", "install", "pyflyby"],
        stdout=subprocess.DEVNULL,
        stderr=subprocess.DEVNULL,
    ).wait()
    ipython.run_line_magic("load_ext pyflyby", "inline")
    print("installing isort")
    subprocess.Popen(
        ["pip", "install", "isort"],
        stdout=subprocess.DEVNULL,
        stderr=subprocess.DEVNULL,
    )

A man looking over to a glowing nuclear core with hundreds of wires running from it

What I missed?

I missed the fact that some of these tools like pyflyby and rich already have an ipython extension maintained by the library that just works. It's less complicated and more robust to future changes in the library. If anything ever changes with these I will not have to worry about which version is installed, the extension will just take care of itself.

How to activate these.

The reccomended way is to add them to your ~/.ipython/profile_default/ipython_config.py


c.InteractiveShellApp.extensions.append('rich')
c.InteractiveShellApp.extensions.append('markata')
c.InteractiveShellApp.extensions.append('pyflyby')

The issue that I found with this is that you can end up with a sea of errors flooding your terminal. Personally I will know immediately if ipython is working right or not and typically have scriped venv installs so I have everything I need, so If I don't have everything it's probably for a reason and I don't need an error message lighting up.

My way around this was to test if the module was importable and if it had a load_ipython_extension attribute before appending it as an extension.


def activate_extension(extension):
    try:
        mod = importlib.import_module(extension)
        getattr(mod, "load_ipython_extension")
        c.InteractiveShellApp.extensions.append(extension)
    except ModuleNotFoundError:
        "extension is not installed"
    except AttributeError:
        "extension does not have a 'load_ipython_extension' function"


extensions = ["rich", "markata", "pyflyby"]
for extension in extensions:
    activate_extension(extension)

My Change

If you want to see what I did to my config see this commit.