Re: pairwise combination of two lists
Yingjie Lin yingjie@mssm.edu writes: li1 = ['a', 'b'] li2 = ['1', '2'] and I wish to obtain a list like this li3 = ['a1', 'a2', 'b1', 'b2'] from itertools import * li3 = list(chain.from_iterable(izip(li1,li2))) -- http://mail.python.org/mailman/listinfo/python-list
Re: pairwise combination of two lists
Yingjie Lin yingjie@mssm.edu writes: I have two lists: li1 = ['a', 'b'] li2 = ['1', '2'] and I wish to obtain a list like this li3 = ['a1', 'a2', 'b1', 'b2'] Is there a handy and efficient function to do this, especially when li1 and li2 are long lists. It's not difficult to write your own: def product(l1,l2): for x1 in l1: for x2 in l2: yield x1+x2 use it like: for p in product(l1,l2) ... The call to product() produces a generator, the cross product is never built in full, it should work on long lists. -- Alain. -- http://mail.python.org/mailman/listinfo/python-list
Re: pairwise combination of two lists
On Wed, Aug 17, 2011 at 4:22 PM, Yingjie Lin yingjie@mssm.edu wrote:
Hi Python users,
I have two lists:
li1 = ['a', 'b']
li2 = ['1', '2']
and I wish to obtain a list like this
li3 = ['a1', 'a2', 'b1', 'b2']
Is there a handy and efficient function to do this, especially when li1 and
li2 are long lists.
I found zip() but it only gives [('a', '1'), ('b', '2')], not exactly what I
am looking for.
Use the roundrobin recipe from the itertools documentation.
Cheers,
Ian
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Re: pairwise combination of two lists
On Aug 17, 9:22 pm, Yingjie Lin yingjie@mssm.edu wrote:
I found zip() but it only gives [('a', '1'), ('b', '2')], not exactly what I
am looking for.
Yet, if you feed the zip into a list comprehension you get what you
want:
li3 = [''.join(l) for l in zip(li1,li2)]
Sigmund
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pairwise combination of two lists
Hi Python users,
I have two lists:
li1 = ['a', 'b']
li2 = ['1', '2']
and I wish to obtain a list like this
li3 = ['a1', 'a2', 'b1', 'b2']
Is there a handy and efficient function to do this, especially when li1 and li2
are long lists.
I found zip() but it only gives [('a', '1'), ('b', '2')], not exactly what I
am looking for.
Thank you.
- Yingjie
--
http://mail.python.org/mailman/listinfo/python-list
Re: pairwise combination of two lists
Yingjie Lin wrote:
I have two lists:
li1 = ['a', 'b']
li2 = ['1', '2']
and I wish to obtain a list like this
li3 = ['a1', 'a2', 'b1', 'b2']
Is there a handy and efficient function to do this, especially when li1
and li2 are long lists.
I found zip() but it only gives [('a', '1'), ('b', '2')], not exactly
what I am looking for.
This seems to do it :
mwilson@tecumseth:~$ python
Python 2.6.5 (r265:79063, Apr 16 2010, 13:09:56)
[GCC 4.4.3] on linux2
Type help, copyright, credits or license for more information.
import itertools
li1 = ['a', 'b']
li2 = ['1', '2']
map (lambda (x,y):x+y, list (itertools.product (li1, li2)))
['a1', 'a2', 'b1', 'b2']
Mel.
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Re: pairwise combination of two lists
Mel wrote: Yingjie Lin wrote: I have two lists: li1 = ['a', 'b'] li2 = ['1', '2'] and I wish to obtain a list like this li3 = ['a1', 'a2', 'b1', 'b2'] [ ... ] This seems to do it : mwilson@tecumseth:~$ python Python 2.6.5 (r265:79063, Apr 16 2010, 13:09:56) [GCC 4.4.3] on linux2 Type help, copyright, credits or license for more information. import itertools li1 = ['a', 'b'] li2 = ['1', '2'] map (lambda (x,y):x+y, list (itertools.product (li1, li2))) ['a1', 'a2', 'b1', 'b2'] I have doubts about this in Python3, since tuple unpacking in a argument list isn't done there, and I don't think sum works on strings. Some other function can probably be made to work. Mel. -- http://mail.python.org/mailman/listinfo/python-list
Re: pairwise combination of two lists
In article 98cc6556-11f3-4850-bd2b-30481b530...@mssm.edu,
Yingjie Lin yingjie@mssm.edu wrote:
I have two lists:
li1 = ['a', 'b']
li2 = ['1', '2']
and I wish to obtain a list like this
li3 = ['a1', 'a2', 'b1', 'b2']
Is there a handy and efficient function to do this, especially when li1 and
li2 are long lists.
I found zip() but it only gives [('a', '1'), ('b', '2')], not exactly what I
am looking for.
from itertools import product
li1 = ['a', 'b']
li2 = ['1', '2']
li3 = list(.join(x) for x in product(li1, li2))
li3
['a1', 'a2', 'b1', 'b2']
--
Ned Deily,
n...@acm.org
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Re: pairwise combination of two lists
Yingjie Lin wrote:
Hi Python users,
I have two lists:
li1 = ['a', 'b']
li2 = ['1', '2']
and I wish to obtain a list like this
li3 = ['a1', 'a2', 'b1', 'b2']
Is there a handy and efficient function to do this, especially when li1
and li2 are long lists.
I found zip() but it only gives [('a', '1'), ('b', '2')], not exactly
what I am looking for.
Thank you.
- Yingjie
Hello Yingjie,
This isn't exactly handy, but...
import itertools
a = ('a', 'b')
b = (1, 2)
[x + str(y) for (x, y) in itertools.product(*(a, b))]
['a1', 'a2', 'b1', 'b2']
Cheers,
Kev
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Re: pairwise combination of two lists
Yingjie Lin yingjie@mssm.edu wrote: Hi Python users, I have two lists: li1 = ['a', 'b'] li2 = ['1', '2'] and I wish to obtain a list like this li3 = ['a1', 'a2', 'b1', 'b2'] Is there a handy and efficient function to do this, especially when li1 and li2 are long lists. Depending on your needs, we can offer you three solutions: For our customers who want it all at once, but without any unneccessary waste, the list expression: [a + b for a, b in itertools.product(li1, li2)] or if you don't need the whole list at once (especially interesting for our customers with large lists), the generator expression (genexp): (a + b for a, b in itertools.product(li1, li2)) and if you don't like the throwaway genexp and want something more ecofriedly, we can present you a memory efficient, reusable solution, the generator: def combiner(li1, li2): for a, b in itertools.product(li1, li2): yield a + b ;) HTH, Marc -- http://mail.python.org/mailman/listinfo/python-list
Re: pairwise combination of two lists
This is the easiest and most pythonic way (IMHO): l3 = [i+e for i in li1 for e in li2] l3 ['a1', 'a2', 'b1', 'b2'] Regards, Luis -- http://mail.python.org/mailman/listinfo/python-list
Re: pairwise combination of two lists
On 08/17/2011 01:22 PM, Yingjie Lin wrote:
Hi Python users,
I have two lists:
li1 = ['a', 'b']
li2 = ['1', '2']
and I wish to obtain a list like this
li3 = ['a1', 'a2', 'b1', 'b2']
Is there a handy and efficient function to do this, especially when li1 and li2
are long lists.
I found zip() but it only gives [('a', '1'), ('b', '2')], not exactly what I
am looking for.
Thank you.
- Yingjie
li1 = ['a', 'b']
li2 = ['1', '2']
print [a+b for a in li1 for b in li2]
['a1', 'a2', 'b1', 'b2']
Gary Herron
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