How is the logical processing being done for strings like 'Dog' and 'Cat'
Hi all,
I am a novice programmer in Python.
Please could you explain me the results (regarding logical operators).
I get this:
>>> print bool('God' and 'Devil')
True
[This is ok because (any) string is True, so; (True and True) gives
True]
>>> print('God' and 'Devil')
Devil
[This is what I don't get ]
and for that matter,I also checked out this:
>>> 01 and 10
10
What is python doing when we type in ('God' and 'Devil') or key in (01
and 10) ?
--
http://mail.python.org/mailman/listinfo/python-list
How do I sample randomly based on some probability(wightage)?
Hi all, I need to randomly sample from a list where all choices have weights attached to them. The probability of them being choosen is dependent on the weights. If say Sample list of choices are [A,B,C,D,E] and weights of the same are [0.895,0.567,0.765,0.890,0.60] when I draw (say 2) samples then I want the likeliness of them being chosen be in the order : D>A>C>E>B In short I mean if prob of a H is .9 and probability of T be 0.1 then if I draw 10 samples, 9 should be H and 1 should be T. I coudn't find a function in the module random that does so. Please can someone guide me how the above could be implemented [either through some function which exists and I don't know or pointers to some code snippets which does so]? -- http://mail.python.org/mailman/listinfo/python-list
Re: How do I sample randomly based on some probability(wightage)?
On May 26, 11:39 pm, Sumitava Mukherjee wrote: > Hi all, > I need to randomly sample from a list where all choices have weights > attached to them. The probability of them being choosen is dependent > on the weights. > If say Sample list of choices are [A,B,C,D,E] and weights of the same > are [0.895,0.567,0.765,0.890,0.60] when I draw (say 2) samples then I > want the likeliness of them being chosen be in the order : D>A>C>E>B > > In short I mean if prob of a H is .9 and probability of T be 0.1 then > if I draw 10 samples, 9 should be H and 1 should be T. > > I coudn't find a function in the module random that does so. > Please can someone guide me how the above could be implemented [either > through some function which exists and I don't know or pointers to > some code snippets which does so]? >>>> [Oh, I forgot to mention. I am looking for sampling without replacement.] -- http://mail.python.org/mailman/listinfo/python-list
Re: How do I sample randomly based on some probability(wightage)?
On May 28, 3:52 pm, Antoon Pardon wrote: > Op 2009-05-26, Arnaud Delobelle schreef : > > > > > Sumitava Mukherjee writes: > > >> On May 26, 11:39 pm, Sumitava Mukherjee wrote: > >>> Hi all, > >>> I need to randomly sample from a list where all choices have weights > >>> attached to them. The probability of them being choosen is dependent > >>> on the weights. > >>> If say Sample list of choices are [A,B,C,D,E] and weights of the same > >>> are [0.895,0.567,0.765,0.890,0.60] when I draw (say 2) samples then I > >>> want the likeliness of them being chosen be in the order : D>A>C>E>B > > > You mean A > D > C > E > B > > >>> In short I mean if prob of a H is .9 and probability of T be 0.1 then > >>> if I draw 10 samples, 9 should be H and 1 should be T. > > >>> I coudn't find a function in the module random that does so. > >>> Please can someone guide me how the above could be implemented [either > >>> through some function which exists and I don't know or pointers to > >>> some code snippets which does so]? > > >>>>>> [Oh, I forgot to mention. I am looking for sampling without > >>>>>> replacement.] > > > If you do sampling without replacement, you need to know the exact > > number of each of A, B, C, D, E in the sample, not just their relative > > frequency. > > As far as I understand, you are given the exact number of each. It is one. > The numbers given are not relative frequencies of appearance but weights > to be attributed for picking them. > > -- > Antoon Pardon Yes, the numbers are weights attributed for picking them. -- http://mail.python.org/mailman/listinfo/python-list
Re: How do I sample randomly based on some probability(wightage)?
On May 27, 8:08 pm, Scott David Daniels wrote:
> Sumitava Mukherjee wrote:
> > I need to randomly sample from a list where all choices have weights
> > attached to them. The probability of them being choosen is dependent
> > on the weights.
>
> I am not sure why everybody is normalizing by dividing the weights.
> This isa possibility (I had fun writing it).
>
> def sample_without_replacement(choices, weights):
> '''Yield elements sampled w/o replacement by weighting'''
> if len(weights) != len(choices):
> raise ValueError('%d choices, but %d weights?' % (
> len(choices), len(weights)))
> if min(weights) < 0:
> raise ValueError('Negative weights?: %s' % (
> [(i, w) for i, w in enumerate(weights) if w < 0]))
>
> # look at only non-zero probabilities
> combined = [(w, v) for w, v in zip(weights, choices) if w > 0]
>
> # Go from highest probability down to reduce expected traversal
> combined.sort(key=operator.itemgetter(0), reverse=True)
>
> total = sum(w for w, v in combined) # sum(weights) also works
> while combined:
> spot = sample = random.random() * total
> for n, (weight, choice) in enumerate(combined):
> spot -= weight
> if spot <= 0:
> break
> else:
> # n, (weight, choice) = 0, combined[0] # Highest probability
> raise ValueError('%f left after choosing %f/%f?: %s' % (
> spot, sample, total, combined))
> yield choice
> total -= weight
> if weight > total * 256: # arbitrary choice for recalculation
> # precision affected, rebuild
> total = sum(w for w, v in combined)
> del combined[n]
> raise ValueError('Samplng more than %d without replacement?' % (
> sum(1 for w in weights if w > 0)))
>
> for n in range(10):
> gen = sample_without_replacement('abcdef', [32,16,8,4,2,1])
> print gen.next(), gen.next(), gen.next()
>
> --Scott David Daniels
> scott.dani...@acm.org
Among all the help (all of which I really appreciate), I found your
solution closest to what I was expecting. Thanks a lot Scott.
--
http://mail.python.org/mailman/listinfo/python-list
Re: Python Installation and Running on Windows Vista
On Sep 9, 3:46 pm, Mchizi_Crazy <[EMAIL PROTECTED]> wrote: > Please help with issue... I heard of compatimbiltity issues and would > like clarification. The win32 installer available from python.org works absolutely fine with Vista. So, go ahead and try it out. It works for all of my friends and myself -- http://mail.python.org/mailman/listinfo/python-list
