Hi folks,
I normally wouldn't bring something like this up here, except I think
that there is possibility of something to be done--a language
documentation clarification if nothing else, though possibly an actual
code change as well.
I've been having an argument with a colleague over the last couple
days over the proper way order of statements when setting up a
try/finally to perform cleanup of some action. On some level we're
both being stubborn I think, and I'm not looking for resolution as to
who's right/wrong or I wouldn't bring it to this list in the first
place. The original argument was over setting and later restoring
os.environ, but we ended up arguing over
threading.Lock.acquire/release which I think is a more interesting
example of the problem, and he did raise a good point that I do want
to bring up.
</prologue>
My colleague's contention is that given
lock = threading.Lock()
this is simply *wrong*:
lock.acquire()
try:
do_something()
finally:
lock.release()
whereas this is okay:
with lock:
do_something()
Ignoring other details of how threading.Lock is actually implemented,
assuming that Lock.__enter__ calls acquire() and Lock.__exit__ calls
release() then as far as I've known ever since Python 2.5 first came
out these two examples are semantically *equivalent*, and I can't find
any way of reading PEP 343 or the Python language reference that would
suggest otherwise.
However, there *is* a difference, and has to do with how signals are
handled, particularly w.r.t. context managers implemented in C (hence
we are talking CPython specifically):
If Lock.__enter__ is a pure Python method (even if it maybe calls some
C methods), and a SIGINT is handled during execution of that method,
then in almost all cases a KeyboardInterrupt exception will be raised
from within Lock.__enter__--this means the suite under the with:
statement is never evaluated, and Lock.__exit__ is never called. You
can be fairly sure the KeyboardInterrupt will be raised from somewhere
within a pure Python Lock.__enter__ because there will usually be at
least one remaining opcode to be evaluated, such as RETURN_VALUE.
Because of how delayed execution of signal handlers is implemented in
the pyeval main loop, this means the signal handler for SIGINT will be
called *before* RETURN_VALUE, resulting in the KeyboardInterrupt
exception being raised. Standard stuff.
However, if Lock.__enter__ is a PyCFunction things are quite
different. If you look at how the SETUP_WITH opcode is implemented,
it first calls the __enter__ method with _PyObjet_CallNoArg. If this
returns NULL (i.e. an exception occurred in __enter__) then "goto
error" is executed and the exception is raised. However if it returns
non-NULL the finally block is set up with PyFrame_BlockSetup and
execution proceeds to the next opcode. At this point a potentially
waiting SIGINT is handled, resulting in KeyboardInterrupt being raised
while inside the with statement's suite, and finally block, and hence
Lock.__exit__ are entered.
Long story short, because Lock.__enter__ is a C function, assuming
that it succeeds normally then
with lock:
do_something()
always guarantees that Lock.__exit__ will be called if a SIGINT was
handled inside Lock.__enter__, whereas with
lock.acquire()
try:
...
finally:
lock.release()
there is at last a small possibility that the SIGINT handler is called
after the CALL_FUNCTION op but before the try/finally block is entered
(e.g. before executing POP_TOP or SETUP_FINALLY). So the end result
is that the lock is held and never released after the
KeyboardInterrupt (whether or not it's handled somehow).
Whereas, again, if Lock.__enter__ is a pure Python function there's
less likely to be any difference (though I don't think the possibility
can be ruled out entirely).
At the very least I think this quirk of CPython should be mentioned
somewhere (since in all other cases the semantic meaning of the
"with:" statement is clear). However, I think it might be possible to
gain more consistency between these cases if pending signals are
checked/handled after any direct call to PyCFunction from within the
ceval loop.
Sorry for the tl;dr; any thoughts?
Hi,
For technical reasons, many functions of the Python standard libraries
implemented in C have positional-only parameters. Example:
-------
$ ./python
Python 3.7.0a0 (default, Feb 25 2017, 04:30:32)
>>> help(str.replace)
replace(self, old, new, count=-1, /) # <== notice "/" at the end
...
>>> "a".replace("x", "y") # ok
'a'
>>> "a".replace(old="x", new="y") # ERR!
TypeError: replace() takes at least 2 arguments (0 given)
-------
When converting the methods of the builtin str type to the internal
"Argument Clinic" tool (tool to generate the function signature,
function docstring and the code to parse arguments in C), I asked if
we should add support for keyword arguments in str.replace(). The
answer was quick: no! It's a deliberate design choice.
Quote of Yury Selivanov's message:
"""
I think Guido explicitly stated that he doesn't like the idea to
always allow keyword arguments for all methods. I.e. `str.find('aaa')`
just reads better than `str.find(needle='aaa')`. Essentially, the idea
is that for most of the builtins that accept one or two arguments,
positional-only parameters are better.
"""
http://bugs.python.org/issue29286#msg285578
I just noticed a module on PyPI to implement this behaviour on Python functions:
https://pypi.python.org/pypi/positional
My question is: would it make sense to implement this feature in
Python directly? If yes, what should be the syntax? Use "/" marker?
Use the @positional() decorator?
Do you see concrete cases where it's a deliberate choice to deny
passing arguments as keywords?
Don't you like writing int(x="123") instead of int("123")? :-) (I know
that Serhiy Storshake hates the name of the "x" parameter of the int
constructor ;-))
By the way, I read that "/" marker is unknown by almost all Python
developers, and [...] syntax should be preferred, but
inspect.signature() doesn't support this syntax. Maybe we should fix
signature() and use [...] format instead?
Replace "replace(self, old, new, count=-1, /)" with "replace(self,
old, new[, count=-1])" (or maybe even not document the default
value?).
Python 3.5 help (docstring) uses "S.replace(old, new[, count])".
Victor
I just spent a few minutes staring at a bug caused by a missing comma
-- I got a mysterious argument count error because instead of foo('a',
'b') I had written foo('a' 'b').
This is a fairly common mistake, and IIRC at Google we even had a lint
rule against this (there was also a Python dialect used for some
specific purpose where this was explicitly forbidden).
Now, with modern compiler technology, we can (and in fact do) evaluate
compile-time string literal concatenation with the '+' operator, so
there's really no reason to support 'a' 'b' any more. (The reason was
always rather flimsy; I copied it from C but the reason why it's
needed there doesn't really apply to Python, as it is mostly useful
inside macros.)
Would it be reasonable to start deprecating this and eventually remove
it from the language?
--
--Guido van Rossum (python.org/~guido)
This is a suggestion that comes up periodically here or on python-dev.
This proposal introduces a way to bind a temporary name to the value
of an expression, which can then be used elsewhere in the current
statement.
The nicely-rendered version will be visible here shortly:
https://www.python.org/dev/peps/pep-0572/
ChrisA
PEP: 572
Title: Syntax for Statement-Local Name Bindings
Author: Chris Angelico <rosuav(a)gmail.com>
Status: Draft
Type: Standards Track
Content-Type: text/x-rst
Created: 28-Feb-2018
Python-Version: 3.8
Post-History: 28-Feb-2018
Abstract
========
Programming is all about reusing code rather than duplicating it. When
an expression needs to be used twice in quick succession but never again,
it is convenient to assign it to a temporary name with very small scope.
By permitting name bindings to exist within a single statement only, we
make this both convenient and safe against collisions.
Rationale
=========
When an expression is used multiple times in a list comprehension, there
are currently several suboptimal ways to spell this, and no truly good
ways. A statement-local name allows any expression to be temporarily
captured and then used multiple times.
Syntax and semantics
====================
In any context where arbitrary Python expressions can be used, a named
expression can appear. This must be parenthesized for clarity, and is of
the form `(expr as NAME)` where `expr` is any valid Python expression,
and `NAME` is a simple name.
The value of such a named expression is the same as the incorporated
expression, with the additional side-effect that NAME is bound to that
value for the remainder of the current statement.
Just as function-local names shadow global names for the scope of the
function, statement-local names shadow other names for that statement.
They can also shadow each other, though actually doing this should be
strongly discouraged in style guides.
Example usage
=============
These list comprehensions are all approximately equivalent::
# Calling the function twice
stuff = [[f(x), f(x)] for x in range(5)]
# Helper function
def pair(value): return [value, value]
stuff = [pair(f(x)) for x in range(5)]
# Inline helper function
stuff = [(lambda v: [v,v])(f(x)) for x in range(5)]
# Extra 'for' loop - see also Serhiy's optimization
stuff = [[y, y] for x in range(5) for y in [f(x)]]
# Expanding the comprehension into a loop
stuff = []
for x in range(5):
y = f(x)
stuff.append([y, y])
# Using a statement-local name
stuff = [[(f(x) as y), y] for x in range(5)]
If calling `f(x)` is expensive or has side effects, the clean operation of
the list comprehension gets muddled. Using a short-duration name binding
retains the simplicity; while the extra `for` loop does achieve this, it
does so at the cost of dividing the expression visually, putting the named
part at the end of the comprehension instead of the beginning.
Statement-local name bindings can be used in any context, but should be
avoided where regular assignment can be used, just as `lambda` should be
avoided when `def` is an option.
Open questions
==============
1. What happens if the name has already been used? `(x, (1 as x), x)`
Currently, prior usage functions as if the named expression did not
exist (following the usual lookup rules); the new name binding will
shadow the other name from the point where it is evaluated until the
end of the statement. Is this acceptable? Should it raise a syntax
error or warning?
2. The current implementation [1] implements statement-local names using
a special (and mostly-invisible) name mangling. This works perfectly
inside functions (including list comprehensions), but not at top
level. Is this a serious limitation? Is it confusing?
3. The interaction with locals() is currently[1] slightly buggy. Should
statement-local names appear in locals() while they are active (and
shadow any other names from the same function), or should they simply
not appear?
4. Syntactic confusion in `except` statements. While technically
unambiguous, it is potentially confusing to humans. In Python 3.7,
parenthesizing `except (Exception as e):` is illegal, and there is no
reason to capture the exception type (as opposed to the exception
instance, as is done by the regular syntax). Should this be made
outright illegal, to prevent confusion? Can it be left to linters?
5. Similar confusion in `with` statements, with the difference that there
is good reason to capture the result of an expression, and it is also
very common for `__enter__` methods to return `self`. In many cases,
`with expr as name:` will do the same thing as `with (expr as name):`,
adding to the confusion.
References
==========
.. [1] Proof of concept / reference implementation
(https://github.com/Rosuav/cpython/tree/statement-local-variables)
Copyright
=========
This document has been placed in the public domain.
..
Local Variables:
mode: indented-text
indent-tabs-mode: nil
sentence-end-double-space: t
fill-column: 70
coding: utf-8
End:
That should probably be its own thread
From: Python-ideas [mailto:python-ideas-bounces+tritium-list=sdamon.com@python.org] On Behalf Of Robert Vanden Eynde
Sent: Wednesday, February 28, 2018 4:48 PM
Cc: python-ideas <python-ideas(a)python.org>
Subject: Re: [Python-ideas] PEP 572: Statement-Local Name Bindings
We are currently like a dozen of people talking about multiple sections of a single subject.
Isn't it easier to talk on a forum?
Am I the only one who thinks mailing list isn't easy when lots of people talking about multiple subjects?
Of course we would put the link in the mailing list so that everyone can join.
A forum (or just few "issues" thread on github) is where we could have different thread in parallel, in my messages I end up with like 10 comments not all related, in a forum we could talk about everything and it would still be organized by subjects.
Also, it's more interactive than email on a global list, people can talk to each other in parallel, if I want to answer about a mail that was 10 mail ago, it gets quickly messy.
We could all discuss on a gist or some "Issues" thread on GitHub.
2018-02-28 22:38 GMT+01:00 Robert Vanden Eynde <robertve92(a)gmail.com <mailto:robertve92@gmail.com> >:
Le 28 févr. 2018 11:43, "Chris Angelico" <rosuav(a)gmail.com <mailto:rosuav@gmail.com> > a écrit :
> It's still right-to-left, which is as bad as middle-outward once you
> combine it with normal left-to-right evaluation. Python has very
> little of this [..]
I agree [....]
>> 2) talking about the implementation of thektulu in the "where =" part.
> ?
In the Alternate Syntax, I was talking about adding a link to the thektulu (branch where-expr) <https://github.com/thektulu/cpython/commits/where-expr>
implementation as a basis of proof of concept (as you did with the other syntax).
>> 3) "C problem that an equals sign in an expression can now create a name inding, rather than performing a comparison."
As you agreed, with the "ch with ch = getch()" syntax we won't accidentally switch a "==" for a "=".
I agree this syntax :
```
while (ch with ch = getch()):
...
```
doesn't read very well, but in the same way as in C or Java while(ch = getch()){} or worse ((ch = getch()) != null) syntax.
Your syntax "while (getch() as ch):" may have a less words, but is still not clearer.
As we spoke on Github, having this syntax in a while is only useful if the variable does leak.
>> 5) Any expression vs "post for" only
> I don't know what the benefit is here, but sure. As long as the
> grammar is unambiguous, I don't see any particular reason to reject
> this.
I would like to see a discussion of pros and cons, some might think like me or disagree, that's a strong langage question.
> 6) with your syntax, how does the simple case work (y+2 with y = x+1) ?
What simple case? The case where you only use the variable once? I'd
write it like this:
(x + 1) + 2
>> The issue is not only about reusing variable.
> If you aren't using the variable multiple times, there's no point
> giving it a name. Unless I'm missing something here?
Yes, variables are not there "just because we reuse them", but also to include temporary variables to better understand the code.
Same for functions, you could inline functions when used only once, but you introduce them for clarity no ?
```
a = v ** 2 / R # the acceleration in a circular motion
f = m * a # law of Newton
```
could be written as
```
f = m * (v ** 2 / R) # compute the force, trivial
```
But having temporary variables help a lot to understand the code, otherwise why would we create temporary variables ?
I can give you an example where you do a process and each time the variable is used only one.
>> 8)
>> (lambda y: [y, y])(x+1)
>> Vs
>> (lambda y: [y, y])(y=x+1)
Ewww. Remind me what the benefit is of writing the variable name that
many times? "Explicit" doesn't mean "utterly verbose".
Yep it's verbose, lambdas are verbose, that's why we created this PEP isn't it :)
> 10) Chaining, in the case of the "with =", in thektulu, parenthesis were
> mandatory:
>
> print((z+3 with z = y+2) with y = x+2)
>
> What happens when the parenthesis are dropped ?
>
> print(z+3 with y = x+2 with z = y+2)
>
> Vs
>
> print(z+3 with y = x+2 with z = y+2)
>
> I prefer the first one be cause it's in the same order as the "post for"
>
> [z + 3 for y in [ x+2 ] for z in [ y+2 ]]
> With my proposal, the parens are simply mandatory. Extending this to
> make them optional can come later.
Indeed, but that's still questions that can be asked.
>> 11) Scoping, in the case of the "with =" syntax, I think the parenthesis
>> introduce a scope :
>>
>> print(y + (y+1 where y = 2))
>>
>> Would raise a SyntaxError, it's probably better for the variable beeing
>> local and not in the current function (that would be a mess).
>>
>> Remember that in list comp, the variable is not leaked :
>>
>> x = 5
>> stuff = [y+2 for y in [x+1]
>> print(y) # SyntaxError
> Scoping is a fundamental part of both my proposal and the others I've
> seen here. (BTW, that would be a NameError, not a SyntaxError; it's
> perfectly legal to ask for the name 'y', it just hasn't been given any
> value.) By my definition, the variable is locked to the statement that
> created it, even if that's a compound statement. By the definition of
> a "(expr given var = expr)" proposal, it would be locked to that
> single expression.
Confer the discussion on scoping on github (https://github.com/python/peps/commit/2b4ca20963a24cf5faac054226857ea9705...) :
"""
In the current implementation it looks like it is like a regular assignment (function local then).
Therefore in the expression usage, the usefulness would be debatable (just assign before).
But in a list comprehension after the for (as I mentioned in my mail), aka. when used as a replacement for for y in [ x + 1 ] this would make sense.
But I think that it would be much better to have a local scope, in the parenthesis. So that print(y+2 where y = x + 1) wouldn't leak y. And when there are no parenthesis like in a = y+2 where y = x+1, it would imply one, giving the same effect as a = (y+2 where y = x+1). Moreover, it would naturally shadow variables in the outermost scope.
This would imply while data where data = sock.read(): does not leak data but as a comparison with C and Java, the syntax while((data = sock.read()) != null) is really really ugly and confusing.
"""
What little documentation I could find, providing a stride on the
assignment target for a list is supposed to trigger 'advanced slicing'
causing element-wise replacement - and hence requiring that the source
iterable has the appropriate number of elements.
>>> a = [0,1,2,3]
>>> a[::2] = [4,5]
>>> a
[4, 1, 5, 3]
>>> a[::2] = [4,5,6]
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: attempt to assign sequence of size 3 to extended slice of size 2
This is in contrast to regular slicing (*without* a stride), allowing to
replace a *range* by another sequence of arbitrary length.
>>> a = [0,1,2,3]
>>> a[:3] = [4]
>>> a
[4, 3]
Issue
=====
When, however, a stride of `1` is specified, advanced slicing is not
triggered.
>>> a = [0,1,2,3]
>>> a[:3:1] = [4]
>>> a
[4, 3]
If advanced slicing had been triggered, there should have been a ValueError
instead.
Expected behaviour:
>>> a = [0,1,2,3]
>>> a[:3:1] = [4]
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: attempt to assign sequence of size 1 to extended slice of size 3
I think that is an inconsistency in the language that should be fixed.
Why do we need this?
====================
One may want this as extra check as well so that list does not change
size. Depending on implementation, it may come with performance benefits
as well.
One could, though, argue that you still get the same result if you do all
correctly
>>> a = [0,1,2,3]
>>> a[:3:1] = [4,5,6]
>>> a
[4, 5, 6, 3]
But I disagree that there should be no error when it is wrong.
*Strides that are not None should always trigger advanced slicing.*
Other Data Types
================
This change should also be applied to bytearray, etc., though see below.
Concerns
========
It may break some code that uses advanced slicing and expects regular
slicing to occur? These cases should be rare, and the error message should
be clear enough to allow fixes? I assume these cases should be
exceptionally rare.
If the implementation relies on `slice.indices(len(seq))[2] == 1` to
determine about advance slicing or not, that would require some
refactoring. If it is only `slice.stride in (1, None)` then this could
easily replaced by checking against None.
Will there be issues with syntax consistency with other data types, in
particular outside the core library?
- I always found that the dynamic behaviour of lists w/r non-advanced
slicing to be somewhat peculiar in the first place, though, undeniably, it
can be immensely useful.
- Most external data types with fixed memory such as numpy do not have this
dynamic flexibility, and the behavior of regular slicing on assignment is
the same as regular slicing. The proposed change would increase
consistency with these other data types.
More surprises
==============
>>> import array
>>> a[1::2] = a[3:3]
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: attempt to assign sequence of size 0 to extended slice of size 2
whereas
>>> a = [1,2,3,4,5]
>>> a[1::2] = a[3:3]
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: attempt to assign sequence of size 0 to extended slice of size 2
>>> a = bytearray(b'12345')
>>> a[1::2] = a[3:3]
>>> a
bytearray(b'135')
but numpy
>>> import numpy as np
>>> a = np.array([1,2,3,4,5])
>>> a[1::2] = a[3:3]
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: could not broadcast input array from shape (0) into shape (2)
and
>>> import numpy as np
>>> a[1:2] = a[3:3]
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: could not broadcast input array from shape (0) into shape (1)
The latter two as expected. memoryview behaves the same.
Issue 2
=======
Whereas NumPy is know to behave differently as a data type with fixed
memory layout, and is not part of the standard library anyway, the
difference in behaviour between lists and arrays I find disconcerting.
This should be resolved to a consistent behaviour.
Proposal 2
==========
Arrays and bytearrays should should adopt the same advanced slicing
behaviour I suggest for lists.
Concerns 2
==========
This has the potential for a lot more side effects in existing code, but as
before in most cases error message should be triggered.
Summary
=======
I find it it not acceptable as a good language design that there is a large
range of behaviour on slicing in assignment target for the different
native (and standard library) data type of seemingly similar kind, and that
users have to figure out for each data type by testing - or at the very
least remember if documented - how it behaves on slicing in assignment
targets. There should be a consistent behaviour at the very least, ideally
even one with a clear user interface as suggested for lists.
-Alexander
As far as I can see, a comprehension like
alist = [f(x) for x in range(10)]
is better than a for-loop
for x in range(10):
alist.append(f(x))
because the previous one shows every element of the list explicitly so that we don't need to handle `append` mentally.
But when it comes to something like
[f(x) + g(f(x)) for x in range(10)]
you find you have to sacrifice some readableness if you don't want two f(x) which might slow down your code.
Someone may argue that one can write
[y + g(y) for y in [f(x) for x in range(10)]]
but it's not as clear as to show what `y` is in a subsequent clause, not to say there'll be another temporary list built in the process.
We can even replace every comprehension with map and filter, but that would face the same problems.
In a word, what I'm arguing is that we need a way to assign temporary variables in a comprehension.
In my opinion, code like
[y + g(y) for x in range(10) **some syntax for `y=f(x)` here**]
is more natural than any solution we now have.
And that's why I pro the new syntax, it's clear, explicit and readable, and is nothing beyond the functionality of the present comprehensions so it's not complicated.
And I hope the discussion could focus more on whether we should allow assigning temporary variables in comprehensions rather than how to solve the specific example I mentioned above.
Good day all,
as a continuation of thread "OS related file operations (copy, move,
delete, rename...) should be placed into one module"
https://mail.python.org/pipermail/python-ideas/2017-January/044217.html
please consider making pathlib to a central file system module with putting
file operations (copy, move, delete, rmtree etc) into pathlib.
BR,
George
The numbers module provides very useful ABC for the 'numeric tower', able to abstract away the differences between python primitives and for example numpy primitives.
I could not find any equivalent for Booleans.
However numpy defines np.bool too, so being able to have an abstract Boolean class for both python bool and numpy bool would be great.
Here is a version that I included in valid8 in the meantime
-----------------------
class Boolean(metaclass=ABCMeta):
"""
An abstract base class for booleans, similar to what is available in numbers
see https://docs.python.org/3.5/library/numbers.html
"""
__slots__ = ()
@abstractmethod
def __bool__(self):
"""Return a builtin bool instance. Called for bool(self)."""
@abstractmethod
def __and__(self, other):
"""self & other"""
@abstractmethod
def __rand__(self, other):
"""other & self"""
@abstractmethod
def __xor__(self, other):
"""self ^ other"""
@abstractmethod
def __rxor__(self, other):
"""other ^ self"""
@abstractmethod
def __or__(self, other):
"""self | other"""
@abstractmethod
def __ror__(self, other):
"""other | self"""
@abstractmethod
def __invert__(self):
"""~self"""
# register bool and numpy bool_ as virtual subclasses
# so that issubclass(bool, Boolean) = issubclass(np.bool_, Boolean) = True
Boolean.register(bool)
try:
import numpy as np
Boolean.register(np.bool_)
except ImportError:
# silently escape
pass
---------------------------
If that topic was already discussed and settled in the past, please ignore this thread - apologies for not being able to find it.
Best regards
Sylvain
Hi,
This mail is the consequence of a true story, a story where CPython
got defeated by Javascript, Java, C# and Go.
One of the teams of the company where Im working had a kind of
benchmark to compare the different languages on top of their
respective "official" web servers such as Node.js, Aiohttp, Dropwizard
and so on. The test by itself was pretty simple and tried to test the
happy path of the logic, a piece of code that fetches N rules from
another system and then apply them to X whatevers also fetched from
another system, something like that
def filter(rule, whatever):
if rule.x in whatever.x:
return True
rules = get_rules()
whatevers = get_whatevers()
for rule in rules:
for whatever in whatevers:
if filter(rule, whatever):
cnt = cnt + 1
return cnt
The performance of Python compared with the other languages was almost
x10 times slower. It's true that they didn't optimize the code, but
they did not for any language having for all of them the same cost in
terms of iterations.
Once I saw the code I proposed a pair of changes, remove the call to
the filter function making it "inline" and caching the rule's
attributes, something like that
for rule in rules:
x = rule.x
for whatever in whatevers:
if x in whatever.x:
cnt += 1
The performance of the CPython boosted x3/x4 just doing these "silly" things.
The case of the rule cache IMHO is very striking, we have plenty
examples in many repositories where the caching of none local
variables is a widely used pattern, why hasn't been considered a way
to do it implicitly and by default?
The case of the slowness to call functions in CPython is quite
recurrent and looks like its an unsolved problem at all.
Sure I'm missing many things, and I do not have all of the
information. This mail wants to get all of this information that might
help me to understand why we are here - CPython - regarding this two
slow patterns.
This could be considered an unimportant thing, but its more relevant
than someone could expect, at least IMHO. If the default code that you
can write in a language is by default slow and exists an alternative
to make it faster, this language is doing something wrong.
BTW: pypy looks like is immunized [1]
[1] https://gist.github.com/pfreixes/d60d00761093c3bdaf29da025a004582
--
--pau
