Python virtual environments

In a short session at the 2018 Python Language Summit, Steve Dower brought up the shortcomings of Python virtual environments, which are meant to create isolated installations of the language and its modules. He said his presentation was "co-written with Twitter" and, indeed, most of his slides were of tweets. At the end, he also slipped in an announcement of his plans for hosting a core development sprint in September.

The title of the session was taken from David Beazley's tweet on May 1: "Virtual environments. Not even once." Thomas Wouters defended virtual environments in a response:

But Beazley and others (including Dower) think that starting Python tutorials or training classes with a 20-minute digression on setting up a virtual environment is wasted time. It does stop pip install from messing with the global environment, but it has little or nothing to do with actually learning Python. Dower noted that Pipenv is supposed to solve some of the problems with virtual environments, but it "feels a bit clunky", according to a tweet by Trey Hunner.

In another Twitter "thread", there was a discussion of potential changes to pip so that it would gain the notion of local versus global installation. That might be a path toward solving the problems that folks see with virtual environments and Pipenv. Dower said he is willing to create a PEP if there is a consensus on a way forward.

He would like to see a way to do local package installation without using virtual environments. He also would like to have a way to invoke the "right" Python (the right version from the right location) without using virtual environments. But for those who are using virtual environments, he would like them to be relocatable, so that users can copy them elsewhere and have them still be functional. Barry Warsaw suggested making pip --user the default as it is in Debian and Ubuntu; Dower said that only "localizes the damage" and doesn't really solve the problem.

Core development sprint

Dower has volunteered to host a core development sprint to work on CPython. He has scheduled it for September 10-14, 2018 in Redmond, Washington on the campus of his employer, Microsoft. They will have an entire building to use for the sprint. There will be a hotel block reserved in Bellevue, since it is a more interesting place to stay, he said. Around 25-30 developers will be invited to attend; active developers or those with a PEP under consideration should expect to get an invite. He is hoping that the Python Software Foundation will pick up the travel expenses for the invitees, but any core developer is welcome to attend.

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