gh-72327: Suggest using system terminal for pip install in PyREPL

[ichard26]

Users new to Python packaging often try to use pip from the REPL only to be met with a confusing SyntaxError. If this happens, guide the user to use a system terminal instead to invoke pip. The pip project still receives the occasional issue from users lamenting that "pip is not working!" (pypa/pip#13409)

This is an updated version of #8536.

cc @ncoghlan

• Issue: Give better errors for OS commands, like 'pip', in REPL, script #72327

[brianschubert]

The new REPL has a similar special case for when await is used at the top-level:

cpython/Lib/_pyrepl/console.py

Lines 210 to 217 in 1953713

	except SyntaxError as e:
	if e.args[0] == "'await' outside function":
	python = os.path.basename(sys.executable)
	e.add_note(
	f"Try the asyncio REPL ({python} -m asyncio) to use"
	f" top-level 'await' and run background asyncio tasks."
	)
	self.showsyntaxerror(filename, source=source)

Maybe this could be done in a similar way?

Something like this might work:

:...skipping... diff --git a/Lib/_pyrepl/console.py b/Lib/_pyrepl/console.py index 8956fb1242e..833e79ef3c2 100644 --- a/Lib/_pyrepl/console.py +++ b/Lib/_pyrepl/console.py @@ -195,7 +195,15 @@ def runsource(self, source, filename="<input>", symbol="single"): ast.PyCF_ONLY_AST, incomplete_input=False, ) - except (SyntaxError, OverflowError, ValueError): + except SyntaxError as e: + if "pip install" in source: # maybe use a more general regex? + e.add_note( + "Did you mean to run the 'pip' command?." + " If so, <insert tip message here>" + ) + self.showsyntaxerror(filename, source=source) + return False + except (OverflowError, ValueError): self.showsyntaxerror(filename, source=source) return False if tree.body:

[adqm]

I teach Python at the university level, and this is a pretty common issue, so I think this would be a good addition! Maybe checking if "pip install" shows up anywhere in the source string is too general, though? That would fire on input like print('pip install"), which I'm not sure is helpful.

I feel like this might want to be a more specific check, like matching the source string against something like ^\s*(py(thon3?)? -m pip|pip3?) install. I suppose you could even check for a variant involving sys.executable, though that's probably overkill (since the likely culprit here is copy/pasting general instructions from somewhere).

[ichard26]

Ah crap, I forgot that force-pushing is frown upon here. Sorry about that!

@brianschubert thanks for the suggestion. Implementing this via the new REPL is much cleaner! I've updated my patch to use your approach.

[jason-fine]

It may be nice to include "or pip3" depending on which version they want to use.

[ichard26]

I really don't want to get into the weeds of how to invoke pip (because the answer is "it depends" and I don't want to make this more complicated). The point of saying "try the 'pip' command" is that it can't simply be copied. The onus is on the user to invoke pip appropriately for their system. In most cases, I expect them to re-copy and paste what they just pasted/typed in.