[issue32486] tail optimization for 'yield from'

[Benjamin Peterson]

Benjamin Peterson  added the comment:

The original yield from implementation did something like this, but we dropped 
it because it caused debuggability problems. See #14230

--
nosy: +benjamin.peterson
resolution:  -> rejected
stage:  -> resolved
status: open -> closed

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[issue32486] tail optimization for 'yield from'

[Terry J. Reedy]

Terry J. Reedy  added the comment:

I think this should have been first floated on python-ideas list.  One 
objection is the same as for eliminating tail calls in general: it collapses 
tracebacks.

def g1():
yield from g2()
def g2():
yield 1/0
for i in g1(): pass

Traceback (most recent call last):
  File "F:\Python\a\tem.py", line 7, in 
for i in g1(): pass
  File "F:\Python\a\tem.py", line 2, in g1
yield from g2()
  File "F:\Python\a\tem.py", line 5, in g2
yield 1/0
ZeroDivisionError: division by zero

There was at least some discussion of making 'yield from' internally more 
efficient without actual replacement.  I don't know what the current CPython 
implementation does.

--
nosy: +terry.reedy

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[issue32486] tail optimization for 'yield from'

[Brett Cannon]

Change by Brett Cannon :


--
versions: +Python 3.7 -Python 3.6

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[issue32486] tail optimization for 'yield from'

[Brett Cannon]

Change by Brett Cannon :


--
type: resource usage -> enhancement

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[issue32486] tail optimization for 'yield from'

[Robert Smart]

New submission from Robert Smart :

When a generator procedure ends with "yield from" it would be nice if this was 
handled efficiently (just replace the generator with the new source). Because 
it is natural to push things back into a generator with

def prependGen(hd,tl):
yield hd
yield from tl

--
messages: 309407
nosy: Robert Smart
priority: normal
severity: normal
status: open
title: tail optimization for 'yield from'
type: resource usage
versions: Python 3.6

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