New submission from Inyeol Lee <[email protected]>:
Simple coroutine with for loop works:
>>> def pack_a():
while True:
L = []
for i in range(2):
L.append((yield))
print(L)
>>> pa = pack_a()
>>> next(pa)
>>> pa.send(1)
>>> pa.send(2)
[1, 2]
>>>
If using list comprehension (generator expression), it fails:
>>> def pack_b():
while True:
L = [(yield) for i in range(2)]
print(L)
>>> pb = pack_b()
<endless loop here>
I understand what's going on here - generator expression is converted to nested
function and there's no way to either stop the execution inside nested function
(since it's not started yet!) or send() a value to its yield expression. Still
I think this behavior is a bug and needs fixed.
- best fix would make it behave the same as for loop.
- if it's not fixable, yield expression inside genexp should not be allowed.
----------
components: Interpreter Core
messages: 122475
nosy: Inyeol.Lee
priority: normal
severity: normal
status: open
title: yield expression inside generator expression does nothing
type: behavior
versions: Python 3.1
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Python tracker <[email protected]>
<http://bugs.python.org/issue10544>
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