At the moment, the array module of the standard library allows to
create arrays of different numeric types and to initialize them from
an iterable (eg, another array).
What's missing is the possiblity to specify the final size of the
array (number of items), especially for large arrays.
I'm thinking of suffix arrays (a text indexing data structure) for
large texts, eg the human genome and its reverse complement (about 6
billion characters from the alphabet ACGT).
The suffix array is a long int array of the same size (8 bytes per
number, so it occupies about 48 GB memory).
At the moment I am extending an array in chunks of several million
items at a time at a time, which is slow and not elegant.
The function below also initializes each item in the array to a given
value (0 by default).
Is there a reason why there the array.array constructor does not allow
to simply specify the number of items that should be allocated? (I do
not really care about the contents.)
Would this be a worthwhile addition to / modification of the array module?
My suggestions is to modify array generation in such a way that you
could pass an iterator (as now) as second argument, but if you pass a
single integer value, it should be treated as the number of items to
Here is my current workaround (which is slow):
def filled_array(typecode, n, value=0, bsize=(1<<22)):
"""returns a new array with given typecode
(eg, "l" for long int, as in the array module)
with n entries, initialized to the given value (default 0)
a = array.array(typecode, [value]*bsize)
x = array.array(typecode)
r = n
while r >= bsize:
r -= bsize
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
Would it be reasonable to start deprecating this and eventually remove
it from the language?
--Guido van Rossum (python.org/~guido)
The french translation of the Python Documentation  has translated
20% of the pageviews of docs.python.org. I think it's the right moment
to push it do docs.python.org. So there's some questions ! And I'd like
TL;DR (with my personal choices):
- URL may be "http://docs.python.org/fr/"
- For localized variations of languages we should use dash and
lowercase like "docs.python.org/pt-br/"
- po files may be hosted on the python's github
- existing script to build doc may be patched to build translations
- each translations may crosslink to others
- untranslated strings may be visually marked as so
I also opened: http://bugs.python.org/issue26546.
# Chronology, dependencies
The only blocking decision here is the URL, (also reviewing my patch
...), with those two, translated docs can be pushed to production, and
the other steps can be discussed and applied one by one.
# The URL
## CCTLD vs path vs subdomain
I think we should use a variation of "docs.python.org/fr/" for
simplicity and clarity.
I think we should avoid using CCTLDs as they're sometime hard or near
impossible to obtain (may cost a lot of time), also some are expensive,
so it's time and money we clearly don't need to loose.
Last possibility I see is to use a subdomain, like fr.docs.python.org or
docs.fr.python.org but I don't think it's the role / responsibility of
the sub-domain to do it.
So I'm for docs.python.org/LANGUAGE_TAG/ (without moving current
documentation inside a /en/).
## Language tag in path
### Dropping the default locale of a language
I personally think we should not show the region in case it's redundant:
so to use "fr" instead of "fr-FR", "de" instead of "de-DE", but keeping
the possibility to use a locale code when it's not redundant like for
"pt-br" or "de-AT" (German ('de') as used in Austria ('AT')).
I think so because I don't think we'll have a lot of locale variations
(like de-AT, fr-CH, fr-CA, ...) so it will be most of the time redundant
(visually heavy, longer to type, longer to read) but we'll still need
some locale (pt-BR typically).
### gettext VS IETF language tag format
gettext goes by using an underscore between language and locale  and
IETF goes by using a dash .
As sphinx is using gettext, and gettext uses underscore we may choose
underscore too. But URLs are not here to leak the underlying
implementation, and the IETF looks like to be the standard way to
represent language tags. Also I visually prefer the dash over the
underscore, so I'm for the dash here.
### Lower case vs upper case local tag
RFC 5646 section-2.1 tells us language tags are not case sensitive, yet
ISO3166-1 recommends that country codes (part of the language tag) be
capitalized. I personally prefer the all-lowercase one as paths in URLs
typically are lowercase. I searched for `inurl:"pt-br"` to see if I'm
not too far away from the usage here and usage seems to agree with me,
although there's some "pt-BR" in urls.
# Where to host the translated files
Currently we're hosting the *po* files in the afpy's (Francophone
association for python)  github  but it may make sense to use (in
the generation scripts) a more controlled / restricted clone in the
python github, at least to have a better view of who can push on the
We may want to choose between aggregating all translations under the
same git repository but I don't feel it's useful.
# How to
Currently, a python script  is used to generate `docs.python.org`, I
proposed a patch in  to make this script clone and build the french
translation too, it's a simple and effective way, I don't think we need
more ? Any idea welcome.
In our side, we have a Makefile  to build the translated doc which
is only a thin layer on top of the Sphinx Makefile. So my proposed patch
to build scripts "just" delegate the build to our Makefile which itself
delegate the hard work to the Sphinx Makefile.
# Next ?
## Document how to translate Python
I think I can (should) write a documentation on "how to start a Python
doc translation project" and "how to migrate existing  python
doc translation projects to docs.python.org" if french does goes
docs.python.org because it may hopefully motivate people to do the same,
and I think our structure is a nice way to do it (A Makefile to generate
the doc, all versions translated, people mainly working on latest
version, scripts to propagating translations to older version, etc...).
## Crosslinking between existing translations
Once the translations are on `docs.python.org`, crosslinks may be
established so people on a version can be aware of other version, and
easily switch to them. I'm not a UI/UX man but I think we may have a
select box right before the existing select box about version, on the
top-left corner. Right before because it'll reflect the path: /fr/3.5/
-> [select box fr][select box 3.5].
## Marking as "untranslated, you can help" the untranslated paragraphs
The translations will always need work to follow upstream modifications:
marking untranslated paragraphs as so may transform the "Oh they suck,
this paragraph is not even translated :-(" to "Hey, nice I can help
translating that !". There's an opened sphinx-doc ticket to do so 
but I have not worked on it yet. As previously said I'm real bad at
designing user interfaces, so I don't even visualize how I'd like it to be.
This is a writeup of a proposal I floated here:
last Sunday. If the response is positive I wish to write a PEP.
Briefly, it is a natural expectation in users that the command:
python -m module_name ...
used to invoke modules in "main program" mode on the command line imported the
module as "module_name". It does not, it imports it as "__main__". An import
within the program of "module_name" makes a new instance of the module, which
causes cognitive dissonance and has the side effect that now the program has
two instances of the module.
What I propose is that the above command line _should_ bind
sys.modules['module_name'] as well as binding '__main__' as it does currently.
I'm proposing that the python -m option have this effect (python pseudocode):
% python -m module.name ...
# pseudocode, with values hardwired for clarity
M = new_empty_module(name='__main__', qualname='module.name')
sys.modules['__main__'] = M
sys.modules['module.name'] = M
# load the module code from wherever (not necessarily a file - CPython
# already must do this phase)
Specificly, this would have the following two changes to current practice:
1) the module is imported _once_, and bound to both its canonical name and
also to __main__.
2) imported modules acquire a new attribute __qualname__ (analogous to the
recent __qualname__ on functions). This is always the conanoical name of the
module as resolved by the importer. For most modules __name__ will be the same
as __qualname__, but for the "main" module __name__ will be '__main__'.
This change has the following advantages:
The current standard boilerplate:
if __name__ == '__main__':
... invoke "main program" here ...
continues to work unchanged.
Importantly, if the program then issues "import module_name", it is already
there and the existing instance is found and used.
The thread referenced above outlines my most recent encounter with this and the
trouble it caused me. Followup messages include some support for this proposed
change, and some criticism.
The critiquing article included some workarounds for this multiple module
situation, but they were (1) somewhat dependent on modules coming from a file
pathname and (2) cumbersome and require every end user to adopt these changes
if affected by the situation. I'd like to avoid that.
Cameron Simpson <cs(a)zip.com.au>
The reasonable man adapts himself to the world; the unreasonable one persists
in trying to adapt the world to himself. Therefore all progress depends
on the unreasonable man. - George Bernard Shaw
Has anyone else found this to be too syntactically noisy?
from module import Foo as _Foo, bar as _bar
That is horrifically noisy IMO. The problem is, how do we
remove the noise without sacrificing intuitiveness? My first
idea was to do this:
from module import_private Foo, bar
And while it's self explanatory, it's also too long. So i
from module _import Foo, bar
I'm leaning more towards the latter, but i'm not loving it
either. Any ideas?
It's common to want to clip (or clamp) a number to a range. This feature
is commonly needed for both floating point numbers and integers:
There are a few approaches:
* use a couple ternary operators
(e.g. https://github.com/scipy/scipy/pull/5944/files line 98, which
generated a lot of discussion)
* use a min/max construction,
* call sorted on a list of the three numbers and pick out the first, or
* use numpy.clip.
Am I right that there is no *obvious* way to do this? If so, I suggest
adding math.clip (or math.clamp) to the standard library that has the
def clip(number, lower, upper):
return lower if number < lower else upper if number > upper else number
This would work for non-numeric types so long as the non-numeric types
support comparison. It might also be worth adding
assert lower < upper
to catch some bugs.
I have run into a use case where I want to create a wrapper object that
will star-unpack a sequence of arguments to pass to a function. Currently
one way to construct this is to create a function:
Such a function feels simple enough, and specific enough to the language,
that it would fit in well in the operator module of the standard library.
We already have a similar representation of this functionality in
Whereas the nested function implementation above will produce unpickleable
objects (due to the closure), a straightforward c implementation will
produce pickleable ones, making them useful for parallel applications.
Maybe it's time to add a new module for sequence-specific functions
(seqtools?). It should contain at least two classes or fabric functions:
1. A view that represents a sliced subsequence. Lazy equivalent of
seq[start:end:step]. This feature is implemented in third-party module
2. A view that represents a linear sequence as 2D array. Iterating this
view emits non-intersecting chunks of the sequence. For example it can
be used for representing the bytes object as a sequence of 1-byte bytes
objects (as in 2.x), a generalized alternative to iterbytes() from PEP
Neither itertools nor collections modules look good place for these
features, since they are not concrete classes and work only with
sequences, not general iterables or iterators. On other side,
mappingproxy and ChainMap look close, maybe new module should be
oriented not on sequences, but on views.
There are currently a few locations in the stdlib, such as http and socket, that are now using
Enums to replace constants; those names are all upper-case -- those aren't the names I am
The names I am speaking of are those in brand-new enumerations where we have full control.
As an example:
NewYear = "First day of the year.", 'absolute', JANUARY, 1
MartinLutherKingJr = "Birth of Civil Rights leader.", 'relative', JANUARY, MONDAY, 3
President = "Birth of George Washington", 'relative', FEBRUARY, MONDAY, 3
Memorial = "Memory of fallen soldiers", 'relative', MAY, MONDAY, 5
Independence = "Declaration of Independence", 'absolute', JULY, 4
Labor = "American Labor Movement", 'relative', SEPTEMBER, MONDAY, 1
Columbus = "Americas discovered", 'relative', OCTOBER, MONDAY, 2
Veterans = "Recognition of Armed Forces service", 'relative', NOVEMBER, 11, 1
Thanksgiving = "Day of Thanks", 'relative', NOVEMBER, THURSDAY, 4
Christmas = "Birth of Jesus Christ", 'absolute', DECEMBER, 25
def __init__(self, doc, type, month, day, occurance=None):
self.__doc__ = doc
self.type = type
self.month = month
self.day = day
self.occurance = occurance
def date(self, year):
returns the observed date of the holiday for `year`
def next_business_day(cls, date, days=1):
Return the next `days` business day from date.
def count_business_days(cls, date1, date2):
Return the number of business days between 'date1' and 'date2'.
def year(cls, year):
Return a list of the actual FederalHoliday dates for `year`.
Take the name "NewYear": if it had been a global constant I would have named it "NEWYEAR"; if
it had been a normal class attribute I would have named it "new_year"; however, being an Enum
member, it is neither of those things.
I've written some custom data types as part of my dbf package, and a few of them have instances
that are singletons that are created in the global (okay, module) namespace, and for them I
followed Python's lead in naming singletons: Python has used Title Case in such things as None,
True, and False, so I followed suit and named mine -- Null, NullDate, NullTime, NullDateTime, etc.
Given my past history with using and creating singleton objects, I followed suit when creating
my own Enum classes.
I was recently queried about my apparent break with PEP 8 for naming Enum members, to which I
> Considering the strange beast that an Enum is, there is not much precedent for it anywhere.
> - Enum is a class
> - but it is a container
> - and can be iterated over
> - and it has a length (which can be zero)
> - but it's always True in a boolean sense
> - Enum members are instances of the Enum class
> - but are pre-created
> - and new ones cannot be created
> - but are available as attributes on the class
> Given all that I have been using Title case (or CamelCase) to name the members as it helps
> distinguish an Enum member from an ordinary attribute (which Enum classes can also have).
I forgot to include in that reply that I think CamelCase also helps to emphasize the special
singleton nature of Enum members.
My question for the community: Your thoughts/opinions of my reasoning, and if you don't agree
then which casing choice would you recommend and use, and why? (Reminder: this question does
not include Enums whose names are replacements for existing constants and so the names cannot
As you all know, the Python stdlib can sometimes be a bit of an
inconsistent mess that can be surprising in how it names things. This is
mostly caused by the fact that several modules were developed before the
introduction of PEP-8, and now we're stuck with the older naming within
It has been said and discussed in the past  that the stdlib is in
fact inconsistent, but fixing this has almost always been disregarded as
being too painful (after all, we don't want a new Python 3 all over again).
However, this way, we will never move away from these inconsistencies.
Perhaps this is fine, but I think we should at least consider providing
function and class names that are unsurprising for developers.
While maintaining full backwards compatibility, my idea is that we should
offer consistently named aliases in -eventually- all stdlib modules. For
instance, with Python 2.6, the threading module received this treatment,
but unfortunately this was not expanded to all modules.
What am I speaking of precisely? I have done a quick survey of the stdlib
and found the following examples. Please note, this is a highly opinionated
list; some names may have been chosen with a very good reason, and others
are just a matter of taste. Hopefully you agree with at least some of them:
* The CamelCasing in some modules are the most obvious culprits, e.g.
logging and unittest. There is obviously an issue regarding subclasses and
methods that are supposed to be overridden, but I feel we could make it
* All lower case class names, such as collections.defaultdict and
collections.deque, should be CamelCased. Another example is datetime, which
uses names such as timedelta instead of TimeDelta.
* Inconsistent names all together, such as re.sub, which I feel should be
re.replace (cf. str.replace). But also re.finditer and re.findall, but no
* Names that do not reflect actual usage, such as ssl.PROTOCOL_SSLv23,
which can in fact not be used as client for SSLv2.
* Underscore usage, such as tarfile.TarFile.gettarinfo (should it not be
get_tar_info?), http.client.HTTPConnection.getresponse vs set_debuglevel,
and pathlib.Path.samefile vs pathlib.Path.read_text. And is it
pkgutil.iter_modules or is it pathlib.Path.iterdir (or re.finditer)?
* Usage of various abbreviations, such as in filecmp.cmp
* Inconsistencies between similar modules, e.g. between
tarfile.TarFile.add and zipfile.ZipFile.write.
These are just some examples of inconsistent and surprising naming I could
find, other categories are probably also conceivable. Another subject for
reconsideration would be attribute and argument names, but I haven't looked
for those in my quick survey.
For all of these inconsistencies, I think we should make a 'consistently'
named alternative, and alias the original variant with them (or the other
way around), without defining a deprecation timeline for the original
names. This should make it possible to eventually make the stdlib
consistent, Pythonic and unsurprising.
What would you think of such an effort?