Re: find sublist inside list
John O'Hagan:
> li=['a', 'c', 'a', 'c', 'c', 'g', 'a', 'c']
> for i in range(len(li)):
> if li[i:i + 2] == ['a', 'c']:
> li[i:i + 2] = ['6']
Oh well, I have done a mistake, it seems.
Another solution then:
>>> 'acaccgac'.replace("ac", chr(6))
'\x06\x06cg\x06'
Bye,
bearophile
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Re: find sublist inside list
On May 4, 4:54 pm, "Gabriel Genellina" wrote:
> En Mon, 04 May 2009 15:12:41 -0300, mzdude escribió:
>
> > substring isn't limited to 0..255
> substring = "\0x%d\0x%d" % (257,257)
> 'acaccgac'.replace("ac", substring)
> > '\x00x257\x00x257\x00x257\x00x257cg\x00x257\x00x257'
>
> This isn't what you think it is. Look carefully:
>
> py> substring = "\0x%d\0x%d" % (257,257)
> py> len(substring)
> 10
> py> list(substring)
> ['\x00', 'x', '2', '5', '7', '\x00', 'x', '2', '5', '7']
>
> --
> Gabriel Genellina
OOPS. My bad. But I'm not going to give up.
l = ['a','b','c','a','c']
us = unicode("".join(l))
substr = unichr(257) + unichr(257)
us = us.replace(u'ac',substr)
print len(us)
print list(us)
output is
>>>
5
[u'a', u'b', u'c', u'\u0101', u'\u0101']
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Re: find sublist inside list
Matthias Gallé wrote: Hi. My problem is to replace all occurrences of a sublist with a new element. Example: Given ['a','c','a','c','c','g','a','c'] I want to replace all occurrences of ['a','c'] by 6 (result [6,6,'c','g',6]). For novelty value: from itertools import izip def replace2(data, pattern): assert len(pattern) == 2 pattern = tuple(pattern) icopy = iter(data) icopy.next() gen = izip(data, icopy) while True: item = gen.next() if item == pattern: yield '6' gen.next() else: yield item[0] # works if list ends with ['a', 'c'] data = ['g', 'a', 'c', 'a', 'c', 'a', 'a', 'a', 'g', 'a', 'c'] want = 'g66aaag6' assert ''.join(replace2(data, ['a', 'c'])) == want # otherwise you lose the last element of the tail data = ['g', 'a', 'c', 'a', 'c', 'a', 'a', 'a', 'g', 'a', 'c', 'c', 'g'] want = 'g66aaag6cg' get = 'g66aaag6c' assert not ''.join(replace2(data, ['a', 'c'])) == want assert ''.join(replace2(data, ['a', 'c'])) == get # fix by adding the pattern to the end of the data as a sentinel def replace2(data, pattern): assert len(pattern) == 2 def _replace2(data, pattern): pattern = tuple(pattern) icopy = iter(data) icopy.next() gen = izip(data, icopy) while True: item = gen.next() if item == pattern: yield '6' gen.next() else: yield item[0] data = data + pattern return list(_replace2(data, pattern))[:-1] data = ['g', 'a', 'c', 'a', 'c', 'a', 'a', 'a', 'g', 'a', 'c'] want = 'g66aaag6' assert ''.join(replace2(data, ['a', 'c'])) == want data = ['g', 'a', 'c', 'a', 'c', 'a', 'a', 'a', 'g', 'a', 'c', 'c', 'g'] want = 'g66aaag6cg' assert ''.join(replace2(data, ['a', 'c'])) == want print 'done' -- http://mail.python.org/mailman/listinfo/python-list
Re: find sublist inside list
Matthias Gallé wrote:
Hi.
My problem is to replace all occurrences of a sublist with a new element.
Example:
Given ['a','c','a','c','c','g','a','c'] I want to replace all
occurrences of ['a','c'] by 6 (result [6,6,'c','g',6]).
If I do this with string ('acaccgac') I have the advantage of all the
'find' functions, but perfomance is bad and some extra care must be
taken if one element consist of more then one character (case of 11 for
example)
So I really would like to work with lists straightforward, but I could
not found anything to search a sublist inside a list.
Any propositions for a simple solution?
For a mutable homogenous array, consider the array module.
Any algorithm that applies to a sequence of chars can be adjusted to
other sequences. For the above case, remember than you can easily
filter None out of a sequence. IE, replace 'a','c' with 6, None and
then filter when done.
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Re: find sublist inside list
En Mon, 04 May 2009 15:12:41 -0300, mzdude escribió:
substring isn't limited to 0..255
substring = "\0x%d\0x%d" % (257,257)
'acaccgac'.replace("ac", substring)
'\x00x257\x00x257\x00x257\x00x257cg\x00x257\x00x257'
This isn't what you think it is. Look carefully:
py> substring = "\0x%d\0x%d" % (257,257)
py> len(substring)
10
py> list(substring)
['\x00', 'x', '2', '5', '7', '\x00', 'x', '2', '5', '7']
--
Gabriel Genellina
--
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Re: find sublist inside list
On May 4, 9:01 am, Matthias Gallé wrote:
> bearophileh...@lycos.com wrote:
> > John O'Hagan:
> >> li=['a', 'c', 'a', 'c', 'c', 'g', 'a', 'c']
> >> for i in range(len(li)):
> >> if li[i:i + 2] == ['a', 'c']:
> >> li[i:i + 2] = ['6']
>
> > Oh well, I have done a mistake, it seems.
> > Another solution then:
>
> 'acaccgac'.replace("ac", chr(6))
> > '\x06\x06cg\x06'
>
> > Bye,
> > bearophile
>
> Thanks bearophile and John for your quick answers.
> Unfortunately, the int that can replace a sublist can be > 255, but
> John's answer looks simple and good enough for me. I will use it as a
> starting point.
>
substring isn't limited to 0..255
>>> substring = "\0x%d\0x%d" % (257,257)
>>> 'acaccgac'.replace("ac", substring)
'\x00x257\x00x257\x00x257\x00x257cg\x00x257\x00x257'
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Re: find sublist inside list
On Mon, 4 May 2009, Francesco Guerrieri wrote: > On Mon, May 4, 2009 at 3:01 PM, John O'Hagan wrote: > > On Mon, 4 May 2009, Matthias Gallé wrote: > > > Hi. > > > > > > My problem is to replace all occurrences of a sublist with a new > > > element. > > > > > > Example: > > > Given ['a','c','a','c','c','g','a','c'] I want to replace all > > > occurrences of ['a','c'] by 6 (result [6,6,'c','g',6]). > > > > li=['a', 'c', 'a', 'c', 'c', 'g', 'a', 'c'] > > for i in range(len(li)): > >if li[i:i + 2] == ['a', 'c']: > >li[i:i + 2] = ['6'] > > > > HTH, > > > > John > > Beware that you are mutating the list you are iterating over. That could > lead to some strange bugs (for instance if you replaced the deleted items > with a longer sequence, the range(len(li)) would still go up to the > original lenght). > It is better to modify a new list instead. Eg you could append to a new > list. [...] Quite right, while it happens to work in this particular example, as you and MRAB point out, it's generally dangerous (and in fact this one silently and uselessly iterates over the last couple of indexes which no longer exist); a new list could be created like this: index=0 newli=[] while indexhttp://mail.python.org/mailman/listinfo/python-list
Re: find sublist inside list
In article , =?ISO-8859-1?Q?Matthias_Gall=E9?= wrote: > >My problem is to replace all occurrences of a sublist with a new element. > >Example: >Given ['a','c','a','c','c','g','a','c'] I want to replace all >occurrences of ['a','c'] by 6 (result [6,6,'c','g',6]). What's your goal? After you do this once, you cannot repeat the operation with a different sublist because you are not tracking the source of the numbers. You might look into standard compression algorithms for information about how to accomplish this. -- Aahz (a...@pythoncraft.com) <*> http://www.pythoncraft.com/ "It is easier to optimize correct code than to correct optimized code." --Bill Harlan -- http://mail.python.org/mailman/listinfo/python-list
Re: find sublist inside list
Matthias Gallé wrote:
bearophileh...@lycos.com wrote:
John O'Hagan:
li=['a', 'c', 'a', 'c', 'c', 'g', 'a', 'c']
for i in range(len(li)):
if li[i:i + 2] == ['a', 'c']:
li[i:i + 2] = ['6']
Oh well, I have done a mistake, it seems.
Another solution then:
'acaccgac'.replace("ac", chr(6))
'\x06\x06cg\x06'
Bye,
bearophile
Thanks bearophile and John for your quick answers.
Unfortunately, the int that can replace a sublist can be > 255, but
John's answer looks simple and good enough for me. I will use it as a
starting point.
John's solution changes the length of the list over which it's
iterating.
I'd suggest something more like:
li = ['a', 'c', 'a', 'c', 'c', 'g', 'a', 'c']
pos = 0
try:
while True:
pos = li.index('a', pos)
if li[pos : pos + 2] == ['a', 'c']:
li[pos : pos + 2] = [6]
pos += 1
except ValueError:
pass
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Re: find sublist inside list
Matthias Gallé:
>the int that can replace a sublist can be > 255,<
You didn't specify your integer ranges.
Probably there are many other solutions for your problem, but you have
to give more information. Like the typical array size, typical range
of the numbers, how much important is total memory used, how much
important is running speed, what kind of processing (or serialization/
output) you later have to do with such arrays, and so on.
Other solutions include using an array('H', []), and using 0-255 to
represent ASCII and numbers >255 <2^16 to represent the other numbers,
etc.
If speed is critical you can even think about creating a little
function with PyInline or D+Pyd, etc.
Bye,
bearophile
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Re: find sublist inside list
bearophileh...@lycos.com wrote:
John O'Hagan:
li=['a', 'c', 'a', 'c', 'c', 'g', 'a', 'c']
for i in range(len(li)):
if li[i:i + 2] == ['a', 'c']:
li[i:i + 2] = ['6']
Oh well, I have done a mistake, it seems.
Another solution then:
'acaccgac'.replace("ac", chr(6))
'\x06\x06cg\x06'
Bye,
bearophile
Thanks bearophile and John for your quick answers.
Unfortunately, the int that can replace a sublist can be > 255, but
John's answer looks simple and good enough for me. I will use it as a
starting point.
Thank's again.
--
Matthias Gallé
Project Symbiose
Centre de Recherche INRIA Rennes - Bretagne Atlantique,
Campus de Beaulieu, 35042 Rennes cedex, France
tel: (33|0) 2 9984 7523
http://www.irisa.fr/symbiose/matthias_galle
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Re: find sublist inside list
On Mon, May 4, 2009 at 3:01 PM, John O'Hagan wrote: > On Mon, 4 May 2009, Matthias Gallé wrote: > > Hi. > > > > My problem is to replace all occurrences of a sublist with a new element. > > > > Example: > > Given ['a','c','a','c','c','g','a','c'] I want to replace all > > occurrences of ['a','c'] by 6 (result [6,6,'c','g',6]). > > > > li=['a', 'c', 'a', 'c', 'c', 'g', 'a', 'c'] > for i in range(len(li)): >if li[i:i + 2] == ['a', 'c']: >li[i:i + 2] = ['6'] > > HTH, > > John > Beware that you are mutating the list you are iterating over. That could lead to some strange bugs (for instance if you replaced the deleted items with a longer sequence, the range(len(li)) would still go up to the original lenght). It is better to modify a new list instead. Eg you could append to a new list. Francesco -- http://mail.python.org/mailman/listinfo/python-list
Re: find sublist inside list
On Mon, 4 May 2009, Matthias Gallé wrote: > Hi. > > My problem is to replace all occurrences of a sublist with a new element. > > Example: > Given ['a','c','a','c','c','g','a','c'] I want to replace all > occurrences of ['a','c'] by 6 (result [6,6,'c','g',6]). > li=['a', 'c', 'a', 'c', 'c', 'g', 'a', 'c'] for i in range(len(li)): if li[i:i + 2] == ['a', 'c']: li[i:i + 2] = ['6'] HTH, John -- http://mail.python.org/mailman/listinfo/python-list
Re: find sublist inside list
Matthias Gallé:
> My problem is to replace all occurrences of a sublist with a new element.
> Example:
> Given ['a','c','a','c','c','g','a','c'] I want to replace all
> occurrences of ['a','c'] by 6 (result [6,6,'c','g',6]).
There are several ways to solve this problem. Representing a string as
a list of "chars" (1-strings) is fine if you work with small strings,
but once they get longer you need too much memory and time.
This is a starting point:
>>> mapper = {"a":6, "c":6}
>>> data = 'acaccgac'
>>> [mapper.get(c, c) for c in data]
[6, 6, 6, 6, 6, 'g', 6, 6]
If you need higher performance, to represent few small numbers into a
well defined string like genomic data, you can use ASCII values of 6
and 11:
>>> from string import maketrans
>>> tab = maketrans("acgt", "".join([chr(6), chr(6), "gt"]))
>>> s.translate(tab)
'\x06\x06\x06\x06\x06g\x06\x06'
Later in processing it's easy to tell apart normal genome bases from
those small numbers.
Note that there is the array.array function too in the standard lib,
and elsewhere there is Numpy too.
There are several other possible solutions, but I stop here so you can
explain your purposes and constraints better.
Bye,
bearophile
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find sublist inside list
Hi.
My problem is to replace all occurrences of a sublist with a new element.
Example:
Given ['a','c','a','c','c','g','a','c'] I want to replace all
occurrences of ['a','c'] by 6 (result [6,6,'c','g',6]).
If I do this with string ('acaccgac') I have the advantage of all the
'find' functions, but perfomance is bad and some extra care must be
taken if one element consist of more then one character (case of 11 for
example)
So I really would like to work with lists straightforward, but I could
not found anything to search a sublist inside a list.
Any propositions for a simple solution?
Thanks in advance,
--
Matthias Gallé
Project Symbiose
Centre de Recherche INRIA Rennes - Bretagne Atlantique,
Campus de Beaulieu, 35042 Rennes cedex, France
tel: (33|0) 2 9984 7523
http://www.irisa.fr/symbiose/matthias_galle
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