testing array of logicals

[John Henry]

Hi list,

Is there a more elagant way of doing this?

# logflags is an array of logicals
test=True
for x in logflags:
test = test and x
print test

--
Thanks,

[Stefan Behnel]

John Henry wrote:
> Is there a more elagant way of doing this?
>
> # logflags is an array of logicals
> test=True
> for x in logflags:
> test = test and x
> print test

Py2.5:

test = all( logflags )

Py2.4 (although somewhat ugly):

try:
test = itertools.ifilterfalse( logflags ).next()
except StopIteration:
test = True

otherwise: your above code will do just fine. Note that you can shortcut,
though, if any of the flags evaluates to False:

test = True
for x in logflags:
if not x:
test = False
break

Stefan

[Fredrik Lundh]

John Henry wrote:

> Is there a more elagant way of doing this?
>
> # logflags is an array of logicals
> test=True
> for x in logflags:
> test = test and x
> print test

your code checks all members, even if the first one's false. that's not
very elegant. here's a better way to do it:

def all(S):
for x in S:
if not x:
return False
return True

print all(logfiles)

if you upgrade to 2.5, you can get rid of the function definition; "all"
is a built-in in 2.5.

also see:

http://www.artima.com/weblogs/viewpost.jsp?thread=98196

</F>

[Ant]

There's reduce, but it's not as explicit, and see F's post RE
efficiency:

>>> x = [True, True, True]
>>> y = [True, False, True]
>>> print reduce(lambda a, b: a and b, x)
True
>>> print reduce(lambda a, b: a and b, y)
False
>>>

[Gary Herron]

The builtin "reduce" does that kind of thing for any function you wish
to apply across the list. So then its only a matter of giving it a
function that "and"s two arguments:

Either:
reduce(lambda a,b: a and b, logFlags)
or
def and2(a,b):
return a and b

reduce(and2, logFlags)

Gary Herron

[Alex Martelli]

John Henry <john10...@hotmail.com> wrote:

test = sum(bool(x) for x in logflags)==len(logflags)

is yet another possibility (without the effectiveness of
shortcircuiting, just like the quoted approach). Some might prefer

test = not sum(not x for x in logflags)

but that's starting to border on the obscure;-).

If by "logicals" you mean "bool" instances (True and False) only, then

test = sum(logflags) == len(logflags)

is simpler and fast than, but equivalent to, my first suggestion.

Alex

[Paul Rubin]

"John Henry" <john10...@hotmail.com> writes:
> # logflags is an array of logicals
> test=True
> for x in logflags:
> test = test and x
> print test

print (False not in map(bool, logflags))

Possibly more "pure" alternative (untested):

from operator import and_
print reduce(and_, map(bool, logflags))

[Simon Brunning]

On 12 Jul 2006 11:14:43 -0700, John Henry <john10...@hotmail.com> wrote:
> Is there a more elagant way of doing this?
>
> # logflags is an array of logicals
> test=True
> for x in logflags:
> test = test and x
> print test

min(logflags)

I feel dirty now. ;-)

--
Cheers,
Simon B,
si...@brunningonline.net,
http://www.brunningonline.net/simon/blog/

[John Henry]

Simon Brunning wrote:
> On 12 Jul 2006 11:14:43 -0700, John Henry <john10...@hotmail.com> wrote:
> > Is there a more elagant way of doing this?
> >
> > # logflags is an array of logicals
> > test=True
> > for x in logflags:
> > test = test and x
> > print test
>
> min(logflags)
>

!!!

> I feel dirty now. ;-)
>

ROFL

Thanks to everybody that replied.

[Simon Brunning]

On 13 Jul 2006 05:45:21 -0700, John Henry <john10...@hotmail.com> wrote:
>
> Simon Brunning wrote:
> >
> > min(logflags)
> >
>
> !!!

Be aware that not only is this an outrageous misuse of min(), it's
also almost certainly much less efficient than /F's suggestion, 'cos
it always iterates through the entire list.

[Bruno Desthuilliers]

Simon Brunning a écrit :

> On 13 Jul 2006 05:45:21 -0700, John Henry <john10...@hotmail.com> wrote:
>
>>
>> Simon Brunning wrote:
>> >
>> > min(logflags)
>> >
>>
>> !!!
>
>
> Be aware that not only is this an outrageous misuse of min(),

+1 QOTW

Ho, my, I've already proposed another one today :(

[Simon Forman]

So many ways.... *drool*
How about:

False not in logflags

(Anybody gonna run all these through timeit? ;P )

[Simon Forman]

>
> False not in logflags
>

Or, if your values aren't already bools

False not in (bool(n) for n in logflags)

Peace,
~Simon

[John Henry]

Very intriguing use of "not in"...

Thanks,

[Janto Dreijer]

John Henry wrote:
> Simon Forman wrote:
> > >
> > > False not in logflags
> > >
> >
> > Or, if your values aren't already bools
> >
> > False not in (bool(n) for n in logflags)
>

> Very intriguing use of "not in"...

Is there a reason why you didn't write
True in (bool(n) for n in logflags)

[Janto Dreijer]

<slaps forehead> doh! Never mind.

[Simon Forman]

*grin*

[H J van Rooyen]

"Janto Dreijer" <jan...@gmail.com> wrote:

*lol* - don't feel bad about this - real programmers make this mistake with a
varying frequency -
>From once every six days or so if you are no good, to once in a lifetime if
you are brilliant, and never only if you are a genius...

First time it bit me I was an apprentice writing in Cobol.

- Hendrik