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Howdy!
Suppose I have a list A containing elements that I want to put into
list B if they satisfy some property. The obvious way of doing it
would be,
B = []
for i in A:
if A.property():
B.append(i)
Now, list comprehensions, map() etc. can make a lot of list operations
easier, but I haven't found a shorter, more elegant way of doing this.
Have I missed something, or will I have to stick to my explicit loops?
Martin
- --
Homepage: http://www.cs.auc.dk/~factotum/
GPG public key: http://www.cs.auc.dk/~factotum/gpgkey.txt
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M3QAnRGXnV3l/KslD7LNxT9roVQhGgJM
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Martin Christensen wrote: B = []
for i in A:
if A.property():
B.append(i)
B = [ i for i in A if i.property() ]
Seems elegant, but then I'd like dictionary-comps if they came along,
Mike
_______________________________________
Mike C. Fletcher
Designer, VR Plumber, Coder http://members.rogers.com/mcfletch/
Martin Christensen wrote: -----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
Howdy!
Suppose I have a list A containing elements that I want to put into
list B if they satisfy some property. The obvious way of doing it
would be,
B = []
for i in A:
if A.property():
B.append(i)
Now, list comprehensions, map() etc. can make a lot of list operations
easier, but I haven't found a shorter, more elegant way of doing this.
Have I missed something, or will I have to stick to my explicit loops?
Martin
B = filter(lambda x: x.property(), A)
David
* Duncan Smith (bu*****@urubu.freeserve.co.uk) wrote:
"Martin Christensen" <kn************************@gvdnet.dk> wrote in message
news:87************@gvdnet.dk... -----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
Howdy!
Suppose I have a list A containing elements that I want to put into
list B if they satisfy some property. The obvious way of doing it
would be,
B = []
for i in A:
if A.property():
B.append(i)
Now, list comprehensions, map() etc. can make a lot of list operations
easier, but I haven't found a shorter, more elegant way of doing this.
Have I missed something, or will I have to stick to my explicit loops?
Martin
Is this the sort of thing you mean?
A = [0, 1, 2, 'four', 'five', 6.0]
[x for x in A if isinstance(x, str)] ['four', 'five']
filter() works well as well:
foo
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9] filter(lambda x: x > 4, foo)
[5, 6, 7, 8, 9]
Jeremy Jones
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1 > "David" == David C Fox <da*******@post.harvard.edu> writes:
David> B = filter(lambda x: x.property(), A)
Now, if I'd paid better attention to the library documentation... :-)
Martin
- --
Homepage: http://www.cs.auc.dk/~factotum/
GPG public key: http://www.cs.auc.dk/~factotum/gpgkey.txt
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5OkAnAgsf4fdEY0j9ekDPOrWytpKPqhJ
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-----END PGP SIGNATURE-----
"Martin Christensen" <kn************************@gvdnet.dk> schrieb im
Newsbeitrag news:87************@gvdnet.dk... -----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
Howdy!
Suppose I have a list A containing elements that I want to put into
list B if they satisfy some property. The obvious way of doing it
would be,
B = []
for i in A:
if A.property():
B.append(i)
Now, list comprehensions, map() etc. can make a lot of list operations
easier, but I haven't found a shorter, more elegant way of doing this.
Have I missed something, or will I have to stick to my explicit loops?
from random import random
rowA1 =[random()]*100000; rowA2=[random()]*100000
rowB1 = rowA1[:]; rowB2 =rowA2[:]
rowC1 = rowA1[:]; rowC2 =rowA2[:]
def A(row1,row2):
for x in row2:
if x<0.5:
row1.append(x)
def B(row1, row2):
row1 += filter(lambda x: x<0.5,row2)
def C(row1, row2):
row1 += [x for x in row2 if x<0.5]
def main():
A(rowA1,rowA2)
B(rowB1,rowB2)
C(rowC1,rowC2)
profile.run("main()")
----------------
Kindly
Michael P
Martin,
Computer Science at Aalborg I see. A Bayes net man perchance? I
hope Uffe, Kristian et al are well. :-)
Duncan
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1 > "Duncan" == Duncan Smith <bu*****@urubu.freeserve.co.uk> writes:
Duncan> Computer Science at Aalborg I see. A Bayes net man perchance?
Duncan> I hope Uffe, Kristian et al are well. :-)
Haha! If you're talking about the guys I'm thinking of, I just came
home from a lovely Friday afternoon beer with them. :-) And yes, I
happen to be doing a project involving Bayesian networks, but I'm
originally a database guy. To keep it relevant, I did my masters
thesis implementation stuff in Python and am very happy I did.
Martin
- --
Homepage: http://www.cs.auc.dk/~factotum/
GPG public key: http://www.cs.auc.dk/~factotum/gpgkey.txt
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iEYEARECAAYFAj9YwPIACgkQYu1fMmOQldWiCwCgr0YsGdB929 LnDvpivNI3C6U/
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"Martin Christensen" <kn************************@gvdnet.dk> wrote in message
news:87************@gvdnet.dk... -----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
>> "Duncan" == Duncan Smith <bu*****@urubu.freeserve.co.uk> writes:
Duncan> Computer Science at Aalborg I see. A Bayes net man perchance?
Duncan> I hope Uffe, Kristian et al are well. :-)
Haha! If you're talking about the guys I'm thinking of, I just came
home from a lovely Friday afternoon beer with them. :-) And yes, I
happen to be doing a project involving Bayesian networks, but I'm
originally a database guy. To keep it relevant, I did my masters
thesis implementation stuff in Python and am very happy I did.
Martin
Yes, messrs. Kjaerulff and Olesen. All my Bayes net stuff is in Python. I
must tidy it up (and rewrite my Digraph class) so I can make it available.
Duncan
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1 > "Duncan" == Duncan Smith <bu*****@urubu.freeserve.co.uk> writes:
Duncan> Yes, messrs. Kjaerulff and Olesen.
Then I'm afraid that we were talking about different people, and these
people are probably less likely to run about getting wet on random
Fridays. :-) They're swell people, though, or at least Kristian is, in
my experience (only know Uffe by sight, hardly even voice). Oh well,
it was still amusing despite the Fates not playing _that_ much with
us.
Martin
- --
Homepage: http://www.cs.auc.dk/~factotum/
GPG public key: http://www.cs.auc.dk/~factotum/gpgkey.txt
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=+uoP
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