[Python-Dev] PEP 550 v4 (original) (raw)

Elvis Pranskevichus elprans at gmail.com
Thu Sep 7 10:13:46 EDT 2017

On Thursday, September 7, 2017 6:37:58 AM EDT Greg Ewing wrote:

2) You ignore it and always use a context manager, in which case it's not strictly necessary for the implicit context push to occur, since the relevant context managers can take care of it.

So there doesn't seem to be any great advantage to the automatic context push, and it has some disadvantages, such as yield-from not quite working as expected in some situations.

The advantage is that context managers don't need to always allocate and push an LC. [1]

Also, it seems that every generator is going to incur the overhead of allocating a logicalcontext even when it doesn't actually change any context vars, which most generators won't.

By default, generators reference an empty LogicalContext object that is allocated once (like the None object). We can do that because LCs are immutable. 

                      Elvis

[1] https://mail.python.org/pipermail/python-dev/2017-September/ 149265.html

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