Re: Newbie regular expression and whitespace question
"Fredrik Lundh" <[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED] > > > timeit -s "import test" "test.test3()" > 100 loops, best of 3: 6.73 msec per loop > > > timeit -s "import test" "test.test4()" > 1 loops, best of 3: 27.8 usec per loop > > that's a 240x slowdown. hmm. > > > > Well, what of it? How fast does it have to be? Is it a one-shot conversion? People tend to be willing to wait a bit longer for one-time conversion programs. What else is going on in this program? Is this the bottleneck? Are we reading the input over the Internet through HTTP? If I'm running this program and waiting for the results, 7 msec isn't perceptibly slower than 28 usec - both are going to seem pretty much instantaneous. On the other hand, if I'm processing 100 files, then this goes up to, um, .7 sec vs 3 msec. There is no question, regexp's beat the pants off of pyparsing in raw performance. But this newsgroup has visited the raw performance issue many times in the past, usually when responding to the "Python can't be very fast, it's interpreted" argument. Raw performance is just one aspect in determining suitability of a given technical approach. -- Paul -- http://mail.python.org/mailman/listinfo/python-list
Re: Newbie regular expression and whitespace question
Thanks for the great positive responses. I was close with what I was trying, I guess, but close only counts in horseshoes and um.. something else that close counts in. :-) googleboy -- http://mail.python.org/mailman/listinfo/python-list
Re: Newbie regular expression and whitespace question
"googleboy" <[EMAIL PROTECTED]> wrote:
> Hi.
>
> I am trying to collapse an html table into a single line. Basically,
> anytime I see ">" & "<" with nothing but whitespace between them, I'd
> like to remove all the whitespace, including newlines. I've read the
> how-to and I have tried a bunch of things, but nothing seems to work
> for me:
>
> [snip]
As others have shown you already, you need to use the sub method of the re
module:
import re
regex = re.compile(r'>\s*<')
print regex.sub('><',data)
> For extra kudos (and I confess I have been so stuck on the above
> problem I haven't put much thought into how to do this one) I'd like to
> be able to measure the number of characters between the &
> tags, and then insert a newline character at the end of the next word
> after an arbitrary number of characters. I am reading in to a
> script a bunch of paragraphs formatted for a webpage, but they're all
> on one big long line and I would like to split them for readability.
What I guess you want to do is wrap some text. Do not reinvent the wheel,
there's already a module
for that:
import textwrap
print textwrap.fill(oneBigLongLine, 60)
HTH,
George
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Re: Newbie regular expression and whitespace question
Paul McGuire wrote:
> If you're absolutely stuck on using RE's, then others will have to step
> forward. Meanwhile, here's a pyparsing solution (get pyparsing at
> http://pyparsing.sourceforge.net):
so, let's see. using ...
from pyparsing import *
import re
data = """ ... table example from op ... """
def test1():
LT = Literal("<")
GT = Literal(">")
collapsableSpace = GT + LT
collapsableSpace.setParseAction( replaceWith("><") )
return collapsableSpace.transformString(data)
def test2():
return re.sub(">\s+<", "><", data)
I get
> timeit -s "import test" "test.test1()"
100 loops, best of 3: 6.8 msec per loop
> timeit -s "import test" "test.test2()"
1 loops, best of 3: 33.3 usec per loop
or in other words, five lines instead of one, and a 200x slowdown.
but alright, maybe we should precompile the expressions to get a
fair comparision. adding
LT = Literal("<")
GT = Literal(">")
collapsableSpace = GT + LT
collapsableSpace.setParseAction( replaceWith("><") )
def test3():
return collapsableSpace.transformString(data)
p = re.compile(">\s+<")
def test4():
return p.sub("><", data)
to the first program, I get
> timeit -s "import test" "test.test3()"
100 loops, best of 3: 6.73 msec per loop
> timeit -s "import test" "test.test4()"
1 loops, best of 3: 27.8 usec per loop
that's a 240x slowdown. hmm.
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Re: Newbie regular expression and whitespace question
"googleboy" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> Hi.
>
> I am trying to collapse an html table into a single line. Basically,
> anytime I see ">" & "<" with nothing but whitespace between them, I'd
> like to remove all the whitespace, including newlines. I've read the
> how-to and I have tried a bunch of things, but nothing seems to work
> for me:
>
> --
>
> table = open(r'D:\path\to\tabletest.txt', 'rb')
> strTable = table.read()
>
> #Below find the different sort of things I have tried, one at a time:
>
> strTable = strTable.replace(">\s<", "><") #I got this from the module
> docs
>
> strTable = strTable.replace(">.<", "><")
>
> strTable = ">\s+<".join(strTable)
>
> strTable = ">\s<".join(strTable)
>
> print strTable
>
> --
>
> The table in question looks like this:
>
>
>
>
> Introduction
> 3
>
>
>
>
>
> ONE
> Childraising for Parrots
> 11
>
>
>
>
>
> For extra kudos (and I confess I have been so stuck on the above
> problem I haven't put much thought into how to do this one) I'd like to
> be able to measure the number of characters between the &
> tags, and then insert a newline character at the end of the next word
> after an arbitrary number of characters. I am reading in to a
> script a bunch of paragraphs formatted for a webpage, but they're all
> on one big long line and I would like to split them for readability.
>
> TIA
>
> Googleboy
>
If you're absolutely stuck on using RE's, then others will have to step
forward. Meanwhile, here's a pyparsing solution (get pyparsing at
http://pyparsing.sourceforge.net):
---
from pyparsing import *
LT = Literal("<")
GT = Literal(">")
collapsableSpace = GT + LT# matches with or without intervening
whitespace
collapsableSpace.setParseAction( replaceWith("><") )
print collapsableSpace.transformString(data)
---
The reason this works is that pyparsing implicitly skips over whitespace
while looking for matches of collapsable space (a '>' followed by a '<').
When found, the parse action is triggered, which in this case, replaces
whatever was matched with the string "><". Finally, the input data (in this
case your HTML table, stored in the string variable, data) is passed to
transformString, which scans for matches of the collapsableSpace expression,
runs the parse action when they are found, and returns the final transformed
string.
As for word wrapping within ... tags, there are at least two recipes
in the Python Cookbook for word wrapping. Be careful, though, as many HTML
pages are very bad about omitting the trailing tags.
-- Paul
--
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Re: Newbie regular expression and whitespace question
googleboy a écrit :
> Hi.
>
> I am trying to collapse an html table into a single line. Basically,
> anytime I see ">" & "<" with nothing but whitespace between them, I'd
> like to remove all the whitespace, including newlines. I've read the
> how-to and I have tried a bunch of things, but nothing seems to work
> for me:
>
> --
>
> table = open(r'D:\path\to\tabletest.txt', 'rb')
> strTable = table.read()
>
> #Below find the different sort of things I have tried, one at a time:
>
> strTable = strTable.replace(">\s<", "><") #I got this from the module
> docs
From which module's doc ?
">\s<" is the litteral string ">\s<", not a regular expression. Please
re-read the re module doc, and the re howto (you'll find a link to it in
the re module's doc...)
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Newbie regular expression and whitespace question
Hi.
I am trying to collapse an html table into a single line. Basically,
anytime I see ">" & "<" with nothing but whitespace between them, I'd
like to remove all the whitespace, including newlines. I've read the
how-to and I have tried a bunch of things, but nothing seems to work
for me:
--
table = open(r'D:\path\to\tabletest.txt', 'rb')
strTable = table.read()
#Below find the different sort of things I have tried, one at a time:
strTable = strTable.replace(">\s<", "><") #I got this from the module
docs
strTable = strTable.replace(">.<", "><")
strTable = ">\s+<".join(strTable)
strTable = ">\s<".join(strTable)
print strTable
--
The table in question looks like this:
Introduction
3
ONE
Childraising for Parrots
11
For extra kudos (and I confess I have been so stuck on the above
problem I haven't put much thought into how to do this one) I'd like to
be able to measure the number of characters between the &
tags, and then insert a newline character at the end of the next word
after an arbitrary number of characters. I am reading in to a
script a bunch of paragraphs formatted for a webpage, but they're all
on one big long line and I would like to split them for readability.
TIA
Googleboy
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