Peter wrote:
>> But this can be expensive memory wise. Is there a way to concatenate
>> generator expressions?
>
> itertools.chain()
>
Aha!
import itertools
>>> x = itertools.chain( (x for x in [None,None] if x is not None), [ None ]
>>> ).next()
>>> print x
None
>>> x = itertools.chain( (x fo
This should be trivial:
I am looking to extract the first non-None element in a list, and
"None" otherwise. Here's one implementation:
>>> x = reduce(lambda x,y: x or y, [None,None,1,None,2,None], None)
>>> print x
1
I thought maybe a generator expression would be better, to prevent
iterating
On Thu, Aug 12, 2010 at 2:57 PM, Thomas Jollans wrote:
> On Thursday 12 August 2010, it occurred to wheres pythonmonks to exclaim:
>> [I just hate function call overhead for this.]
>
> I think you've got your priorities wrong. If you want to avoid unnecessary
> overhead
On Thu, Aug 12, 2010 at 2:42 PM, MRAB wrote:
> wheres pythonmonks wrote:
>>
>> Hi!
>>
>> I have on a few occasions now wanted to have inline-exception
>> handling, like the inline if/else operator.
>>
>> For example,
>>
>> The following m
On Thu, Aug 12, 2010 at 2:19 PM, wheres pythonmonks
wrote:
> On Thu, Aug 12, 2010 at 2:08 PM, Thomas Jollans wrote:
>> On Thursday 12 August 2010, it occurred to wheres pythonmonks to exclaim:
>>> try:
>>> f = n / d
>>> except:
>>> f = float(&q
On Thu, Aug 12, 2010 at 2:08 PM, Thomas Jollans wrote:
> On Thursday 12 August 2010, it occurred to wheres pythonmonks to exclaim:
>> try:
>> f = n / d
>> except:
>> f = float("nan")
>
> A catch-all except clause. Never a good idea. It's
Hi!
I have on a few occasions now wanted to have inline-exception
handling, like the inline if/else operator.
For example,
The following might raise ZeroDivisionError:
f = n / d
So, I can look before I leap (which is okay):
f = float("nan") if d == 0 else n/d;
But, what I'd like to be able t
, Aug 5, 2010 at 11:56 AM, Roald de Vries wrote:
> On Aug 5, 2010, at 5:42 PM, wheres pythonmonks wrote:
>>
>> How does "x is not None" make any sense? "not x is None" does make sense.
>>
>> I can only surmise that in this context (preceding is) "not
How does "x is not None" make any sense? "not x is None" does make sense.
I can only surmise that in this context (preceding is) "not" is not a
unary right-associative operator, therefore:
x is not None === IS_NOTEQ(X, None)
Beside "not in" which seems to work similarly, is there other
syntacti
I did the google search... I must be blind as I don't see any hits...
None is negative in Python? (v2.6)
http://www.google.com/search?ie=UTF-8&q=%22none+is+negative%22+python
>>> if None < -999.99: print "hi"
hi
>>>
>>> if -999 > None: print "hi"
hi
>>>
Is there a way to have the co
stead of having code littered with objects strewn across
the namespace.
Maybe there is a Python ABC tutorial out there that can enlighten me?
W
On Tue, Aug 3, 2010 at 10:06 AM, Roald de Vries wrote:
> On Aug 3, 2010, at 2:46 PM, wheres pythonmonks wrote:
>>
>> Hi!
>>
>
Hi!
I have a class (supposed to be an abstract base class):
In python (as opposed to static languages like C++) I don't seed to
subclass the base class, but instead I can simply override the
behavior of stub methods and values.
Is there a preference between between subclassing (C++ approach) and
o
ional-programming
approaches.
On Sat, Jul 31, 2010 at 5:55 AM, Steven D'Aprano
wrote:
> On Sat, 31 Jul 2010 01:02:47 -0400, wheres pythonmonks wrote:
>
>
>>> Hint -- what does [].append(1) return?
>>>
>>>
>> Again, apologies from a Python beginn
ith the child?)
Thanks again from a Perl-to-Python convert!
W
On Fri, Jul 30, 2010 at 11:47 PM, Steven D'Aprano
wrote:
> On Fri, 30 Jul 2010 08:34:52 -0400, wheres pythonmonks wrote:
>
>> Sorry, doesn't the following make a copy?
>>
>>>>>> from collec
I am starting to use pylint to look at my code and I see that it gives a rating.
What values do experienced python programmers get on code not
targeting the benchmark?
I wrote some code, tried to keep it under 80 characters per line,
reasonable variable names, and I got:
0.12 / 10.
Is this a goo
on the difference between that and:
m['key'] = m.get('key',[]).append(1)
Except that the latter works for immutable values as well as containers.
On Fri, Jul 30, 2010 at 8:19 AM, Steven D'Aprano
wrote:
> On Fri, 30 Jul 2010 07:59:52 -0400, wheres pythonmonks wrote
Instead of defaultdict for hash of lists, I have seen something like:
m={}; m.setdefault('key', []).append(1)
Would this be preferred in some circumstances?
Also, is there a way to upcast a defaultdict into a dict? I have also
heard some people use exceptions on dictionaries to catch key
existe
Thanks. I presume this will work for my nested example as well. Thanks again.
On Thu, Jul 29, 2010 at 2:18 PM, Paul Rubin wrote:
> wheres pythonmonks writes:
>> How do I build an "int1" type that has a default value of 1?
>> [Hopefully no speed penalty.]
>> I
Why is the default value of an int zero?
>>> x = int
>>> print x
>>> x()
0
>>>
How do I build an "int1" type that has a default value of 1?
[Hopefully no speed penalty.]
I am thinking about applications with collections.defaultdict.
What if I want to make a defaultdict of defaultdicts of lists?
Thanks ... I thought int was a type-cast (like in C++) so I assumed I
couldn't reference it.
On Wed, Jul 28, 2010 at 9:31 AM, Nick Raptis wrote:
> Ep, that missing line should be:
>
> On 07/28/2010 04:27 PM, Nick Raptis wrote:
>>
>> On 07/28/2010 04:15 PM, wheres py
A new python convert is now looking for a replacement for another perl idiom.
In particular, since Perl is weakly typed, I used to be able to use
unpack to unpack sequences from a string, that I could then use
immediately as integers.
In python, I find that when I use struct.unpack I tend to get
#x27;,'from __main__ import
>>> A3,d',number=10);
9.4334241349350947
So: in-line lambda possible speed improvement. in-line tuple is slow,
passed-in callback, slowest yet?
Is this possibly right?
Hopefully someone can spot the bug?
W
On Fri, Jul 23, 2010 at 4:10 AM, Steven D
ess function call dispatches]
However, it might be more efficient to avoid the function call
overhead completely and pass-in a string which is substituted into a
string code block, compiled, and executed.
W
On Thu, Jul 22, 2010 at 8:12 PM, Carl Banks wrote:
> On Jul 22, 3:34 pm, wheres
overkill.
3. Is there a reference on all the special variables, like __foo__?
4. Is there any work on deparsing (like Perl's deparse) lambda
functions to inline algebra and get a performance gain?
Thanks again for your input,
W
( from Perl-hacker to Python Programmer )
On Sun, Jul 11, 20
ons/938429/scope-of-python-lambda-functions-and-their-parameters
Will try to avoid namespace mangling until next week.
Thanks again,
W
On Sun, Jul 11, 2010 at 2:17 PM, Duncan Booth
wrote:
> wheres pythonmonks wrote:
>
>> I'm an old Perl-hacker, and am trying to Dive in Py
I'm an old Perl-hacker, and am trying to Dive in Python. I have some
easy issues (Python 2.6)
which probably can be answered in two seconds:
1. Why is it that I cannot use print in booleans?? e.g.:
>>> True and print "It is true!"
I found a nice work-around using eval(compile(.,"","exec"))
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