regular expressions
hi.. im parsing the text file containing the details of the testcases failed.From the file i wanted to obtain only the testcase names and enter them in the excel sheet. the pattern of the text file is: FILE : NW_PTH_TFG6_SCEN_4_2_FIFO.c, LINE : 240 TEST FAIL to get entire: 32768 bytes NW_PTH_TFG6_SCEN_4_2_FIFO.c 340 DATA NOT MATCHING, TEST FAIL TEST FAIL SYSCALL_TEST_SCEN_4_1_ALL.c at line 355 FILE:US_TFG7_SCEN_4_1.c,LINE:189, Server side TEST FAIL FAIL BREW_SCEN_4_1.c 219: can't mount FAIL BREW_SCEN_4_1.c 121: can't umount << BREW_SCEN_4_1.c TEST FAIL errno:No such file or directory >> << BREW_SCEN_4_1.c TEST FAIL >> error:Invalid argument i used the ' re module' and its function partition,but im facing problem in obtaining only the testcase names.. if anyone know the answer please help me.. Thanks for ur help. -- http://mail.python.org/mailman/listinfo/python-list
Regular Expressions
What's the way to go about learning Python's regular expressions? I feel like such an idiot - being so strong in a programming language but knowing nothing about RE. -- http://mail.python.org/mailman/listinfo/python-list
Regular Expressions
This is probably a repeated question, but try as I might I was unable to find something similar in the archives. I'm trying to develop a regular expression for recognizing a simplified C-Style string syntax. I need it to be able to handle escape sequences of the form \x where x is any character including ". Here's what I'm trying: \"([^"\\]|(\\.))*\" When I try to get it to recognize something like: "I said, \"Hello!\"" It stops at the first quote after the \. I've used this very same regular expression in a parser generator I have for C++ and it works just fine. Any thoughts on what I'm doing wrong in the Python Reg Ex world? Thanks for the comments & help. Ron -- http://mail.python.org/mailman/listinfo/python-list
Regular Expressions
Hi, I am trying to grab the following string out of a text file using regular _expression_ (re module): "DcaVer"=dword:0640 What I need to do with that string is trim down " "DcaVer"=dword:" and convert the remaining number from hex to dec. I have been trying to figure this out for a while..I am fairly new so please any help would be greatly appreciated. -- http://mail.python.org/mailman/listinfo/python-list
Regular Expressions...
Hi, all. As a recovering Perl guy, I have to admit I don't quite "get" the re module. For example, I'd like to do a few things (I'm going to use phone numbers, 'cause that's what I'm currently dealing with): 12345678900 -- How would I: - Get just the area code? - Get just the seven-digit number? In Perl, I'd so something like m/^1(...)(...)/; and then I'd have that stuff in $1 and $2, respectively. But the Python stuff simply isn't clicking for me. If anyone could supply concrete examples of how to do the problem, above, that would be terrific. Thanks! -Ken -- http://mail.python.org/mailman/listinfo/python-list
Regular Expressions...
Hi, all. As a recovering Perl guy, I have to admit I don't quite "get" the re module. For example, I'd like to do a few things (I'm going to use phone numbers, 'cause that's what I'm currently dealing with): 12345678900 -- How would I: - Get just the area code? - Get just the seven-digit number? In Perl, I'd so something like m/^1(...)(...)/; and then I'd have the numbers in $1 and $2, respectively. But the Python stuff simply isn't clicking for me. If anyone could supply concrete examples of how to do the problem, above, that would be terrific. Thanks! -Ken -- http://mail.python.org/mailman/listinfo/python-list
Regular Expressions
I'm trying to get the Javascript output on when I match the given value in a
var, I want to output that value that I tried to match:
Example JS:
x = '';//some INNERHTML in a document
if(x.innerHTML.match(/(.*)/i))
{
valuefound = RegEx.$1;
}
I've been reading my python book and tutorials and google search and google
code search trying to understand and I'm still not quite understanding how
to do it.
-Lamonte.
--
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regular expressions.
Hey All, I have been playing around with REs and could not get the following code to run. import re vowel = r'[aeiou]' re.findall(vowel, r"vowel") anything wrong I have done? Regards, Atul. -- http://mail.python.org/mailman/listinfo/python-list
Regular expressions
How do I make a regular expression that returns true if the end of the line is an asterisk -- https://mail.python.org/mailman/listinfo/python-list
Regular expressions
Hi I am trying to change "@HWI-ST115:568:B08LLABXX:1:1105:6465:151103 1:N: 0:" to "@HWI-ST115:568:B08LLABXX:1:1105:6465:151103/1". Can anyone help me with the regular expressions needed? Thanks in advance. Maurice -- http://mail.python.org/mailman/listinfo/python-list
Large regular expressions
Hi, So I m trying to use a very large regular expression, basically I have a list of items I want to find in text, its kind of a conjunction of two regular expressions and a big list..not pretty. However everytime I try to run my code I get this exception: OverflowError: regular expression code size limit exceeded I understand that there is a Python imposed limit on the size of the regular expression. And although its not nice I have a machine with 12Gb of RAM just waiting to be used, is there anyway I can alter Python to allow big regular expressions? Could anyone suggest other methods of these kind of string matching in Python? I m trying to see if my swigged alphabet trie is faster than whats possible in Python! Many thanks, Nathan -- http://mail.python.org/mailman/listinfo/python-list
Re: regular expressions
On 4/15/2010 2:57 AM, chaaana wrote: hi.. im parsing the text file containing the details of the testcases failed.From the file i wanted to obtain only the testcase names and enter them in the excel sheet. the pattern of the text file is: FILE : NW_PTH_TFG6_SCEN_4_2_FIFO.c, LINE : 240 TEST FAIL to get entire: 32768 bytes NW_PTH_TFG6_SCEN_4_2_FIFO.c 340 DATA NOT MATCHING, TEST FAIL TEST FAIL SYSCALL_TEST_SCEN_4_1_ALL.c at line 355 FILE:US_TFG7_SCEN_4_1.c,LINE:189, Server side TEST FAIL FAIL BREW_SCEN_4_1.c 219: can't mount FAIL BREW_SCEN_4_1.c 121: can't umount << BREW_SCEN_4_1.c TEST FAIL errno:No such file or directory>> << BREW_SCEN_4_1.c TEST FAIL>> error:Invalid argument I do not see any consistent pattern in the above lines. What output do you see from filtering them? i used the ' re module' and its function partition,but im facing problem in obtaining only the testcase names.. If I could not write a satisfactory re, I would be tempted to write explicit code to process the lines, possibly defining appropriate search states. Terry Jan Reedy -- http://mail.python.org/mailman/listinfo/python-list
Re: regular expressions
On 04/15/2010 11:05 AM, Terry Reedy wrote:
On 4/15/2010 2:57 AM, chaaana wrote:
hi..
im parsing the text file containing the details of the testcases
failed.From the file i wanted to obtain only the testcase names and
enter them in the excel sheet.
the pattern of the text file is:
FILE : NW_PTH_TFG6_SCEN_4_2_FIFO.c, LINE : 240 TEST FAIL to get entire:
32768 bytes
NW_PTH_TFG6_SCEN_4_2_FIFO.c 340 DATA NOT MATCHING, TEST FAIL
TEST FAIL SYSCALL_TEST_SCEN_4_1_ALL.c at line 355
FILE:US_TFG7_SCEN_4_1.c,LINE:189, Server side TEST FAIL
FAIL BREW_SCEN_4_1.c 219: can't mount
FAIL BREW_SCEN_4_1.c 121: can't umount
<< BREW_SCEN_4_1.c TEST FAIL errno:No such file or directory>>
<< BREW_SCEN_4_1.c TEST FAIL>> error:Invalid argument
I do not see any consistent pattern in the above lines.
What output do you see from filtering them?
My guess is that it's the "FILE:...LINE:..." line(s) that the OP
is interested in, in which case one could do something like
r = re.compile(r'^FILE\s*:\s*(.*?),\s*LINE\s*:\s*(\d+)')
for line in file('input.txt'):
m = r.match(line)
if m:
print m.group(1), m.group(2)
Alternatively, if you're in the regexp-avoiding camp, you might
be able to get away with
LINE_BIT = ', LINE : '
for line in file('input.txt'):
if line.startswith('FILE :') and LINE_BIT in line:
leader, _ = line.split(LINE_BIT, 1)
_, fname = leader.split(":", 1)
fname = fname.strip()
print repr(fname)
but that relies on the LINE_BIT remaining constant (the
"LINE:189" doesn't have spaces where the first "LINE : 240" does
have extra spaces; and the same with the extra spaces around the
"FILE" portion).
-tkc
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Compare regular expressions
Hi, I'm writing a program with a large data stream to which modules can connect using regular expressions. Now I'd like to not have to test all expressions every time I get a line, as most of the time, one of them having a match means none of the others can have so. But ofcource there are also cases where a regular expression can "contain" another expression, like in: "^strange line (\w+) and (\w+)$" and "^strange line (\w+) (?:.*?)$" in which case I'd like to first test the seccond and only if it mathces test the seccond. Do anybody know if such a test is possible? if exp0.contains(exp1): ... -- http://mail.python.org/mailman/listinfo/python-list
builtin regular expressions?
Hello, Can anybody tell me the reason(s) why regular expressions are not built into Python like it is the case with Ruby and I believe Perl? Like for example in the following Ruby code line = 'some string' case line when /title=(.*)/ puts "Title is #$1" when /track=(.*)/ puts "Track is #$1" when /artist=(.*)/ puts "Artist is #$1" end I'm sure there are good reasons, but I just don't see them. Python Culture says: 'Explicit is better than implicit'. May it be related to this? Regards, antoine -- http://mail.python.org/mailman/listinfo/python-list
Enumerating Regular Expressions
Hi all, Does anybody know of a module that allows you to enumerate all the strings a particular regular expression describes? Cheers, -Blair -- http://mail.python.org/mailman/listinfo/python-list
Regular expressions question
I have 2 strings: "Global etsi3 *200 ok30 100% 100% Outgoing" and "Global etsi3 * 4 ok 30 100% 100% Outgoing" The difference is "*200" instead of "* 4". Is there ability to write a regular expression that will match both of that strings? -- http://mail.python.org/mailman/listinfo/python-list
Re: Regular Expressions
"Geoff Hill" <[EMAIL PROTECTED]> writes: > What's the way to go about learning Python's regular expressions? I feel > like such an idiot - being so strong in a programming language but knowing > nothing about RE. Read the documentation? -- http://mail.python.org/mailman/listinfo/python-list
Re: Regular Expressions
Hi, a good start: http://diveintopython.org/regular_expressions/index.html On 10 Feb 2007 15:30:04 -0800, Paul Rubin <"http://phr.cx"@nospam.invalid> wrote: "Geoff Hill" <[EMAIL PROTECTED]> writes: > What's the way to go about learning Python's regular expressions? I feel > like such an idiot - being so strong in a programming language but knowing > nothing about RE. Read the documentation? -- http://mail.python.org/mailman/listinfo/python-list -- --- You can't have everything. Where would you put it? -- Steven Wright --- please visit www.serpia.org -- http://mail.python.org/mailman/listinfo/python-list
Re: Regular Expressions
On Feb 11, 10:26 am, "Geoff Hill" <[EMAIL PROTECTED]> wrote: > What's the way to go about learning Python's regular expressions? I feel > like such an idiot - being so strong in a programming language but knowing > nothing about RE. I suggest that you work through the re HOWTO http://www.amk.ca/python/howto/regex/ and by work through, I don't mean "read". I mean as each new concept is introduced: 1. try the given example(s) yourself at the interactive prompt 2. try variations on the examples 3. read the relevant part of the Library Reference Manual Also I'd suggest reading threads in this newsgroup where people are asking for help with re. HTH, John -- http://mail.python.org/mailman/listinfo/python-list
Re: Regular Expressions
"John Machin" <[EMAIL PROTECTED]> writes: > > What's the way to go about learning Python's regular expressions? I feel > > like such an idiot - being so strong in a programming language but knowing > > nothing about RE. > > I suggest that you work through the re HOWTO > http://www.amk.ca/python/howto/regex/ Also remember Zawinski's law: http://fishbowl.pastiche.org/2003/08/18/beware_regular_expressions -- http://mail.python.org/mailman/listinfo/python-list
Re: Regular Expressions
On Feb 10, 6:26 pm, "Geoff Hill" <[EMAIL PROTECTED]> wrote: > What's the way to go about learning Python's regular expressions? I feel > like such an idiot - being so strong in a programming language but knowing > nothing about RE. I highly recommend reading the book "Mastering Regular Expressions," which I believe is published by O'Reilly. It's a great reference and helps peel the onion in terms of working through RE. They are a language unto themselves. A fun brain exercise. -- http://mail.python.org/mailman/listinfo/python-list
Re: Regular Expressions
On 10 Feb 2007 18:58:51 -0800, gregarican <[EMAIL PROTECTED]> wrote: > On Feb 10, 6:26 pm, "Geoff Hill" <[EMAIL PROTECTED]> wrote: > > What's the way to go about learning Python's regular expressions? I feel > > like such an idiot - being so strong in a programming language but knowing > > nothing about RE. > > I highly recommend reading the book "Mastering Regular Expressions," > which I believe is published by O'Reilly. It's a great reference and > helps peel the onion in terms of working through RE. They are a > language unto themselves. A fun brain exercise. > > -- > http://mail.python.org/mailman/listinfo/python-list > Absolutely: Get "Mastering Regular Expressions" by Jeffrey Friedl. Not only is it easy to read, but you'll get a lot of mileage out of regexes in general. Grep, Perl one-liners, Python, and other tools use regexes, and you'll find that they are really clever little creatures once you befriend a few of them. Shawn -- http://mail.python.org/mailman/listinfo/python-list
Re: Regular Expressions
Thanks. O'Reilly is the way I learned Python, and I'm suprised that I didn't think of a book by them earlier. -- http://mail.python.org/mailman/listinfo/python-list
Re: Regular Expressions
Geoff Hill wrote: > What's the way to go about learning Python's regular expressions? I feel > like such an idiot - being so strong in a programming language but knowing > nothing about RE. > > In fact that's a pretty smart stance. A quote attributed variously to Tim Peters and Jamie Zawinski says "Some people, when confronted with a problem, think 'I know, I'll use regular expressions.' Now they have two problems." regards Steve -- Steve Holden +44 150 684 7255 +1 800 494 3119 Holden Web LLC/Ltd http://www.holdenweb.com Skype: holdenweb http://del.icio.us/steve.holden Blog of Note: http://holdenweb.blogspot.com See you at PyCon? http://us.pycon.org/TX2007 -- http://mail.python.org/mailman/listinfo/python-list
Re: Regular Expressions
On Sun, 11 Feb 2007 07:05:30 +, Steve Holden wrote: > Geoff Hill wrote: >> What's the way to go about learning Python's regular expressions? I feel >> like such an idiot - being so strong in a programming language but knowing >> nothing about RE. >> >> > In fact that's a pretty smart stance. That's a little harsh -- regexes have their place, together with pointer arithmetic, bit manipulations, reverse polish notation and goto. The problem is when people use them inappropriately e.g. using a regex when a simple string.find will do. > A quote attributed variously to > Tim Peters and Jamie Zawinski says "Some people, when confronted with a > problem, think 'I know, I'll use regular expressions.' Now they have two > problems." I believe that is correctly attributed to Jamie Zawinski. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: Regular Expressions
On Feb 11, 9:25 pm, Steven D'Aprano <[EMAIL PROTECTED]> wrote: > On Sun, 11 Feb 2007 07:05:30 +, Steve Holden wrote: > > Geoff Hill wrote: > >> What's the way to go about learning Python's regular expressions? I feel > >> like such an idiot - being so strong in a programming language but knowing > >> nothing about RE. > > > In fact that's a pretty smart stance. > > That's a little harsh -- regexes have their place, together with pointer > arithmetic, bit manipulations, reverse polish notation and goto. The > problem is when people use them inappropriately e.g. using a regex when a > simple string.find will do. Thanks for the tip-off, Steve and Steven. Looks like I'll have to start hiding my 12C (datecode 2214) with its "GTO" button under the loose floor-board whenever I hear a knock at the door ;-) Looks like Agner Fog's gone a million, and there'll be a special place in hell for people who combine regexes with bit manipulation, like Navarro & Raffinot. And we won't even mention Heikki Hy,*7g^54d3j+__= -- http://mail.python.org/mailman/listinfo/python-list
Re: Regular Expressions
gregarican wrote: > On Feb 10, 6:26 pm, "Geoff Hill" <[EMAIL PROTECTED]> wrote: >> What's the way to go about learning Python's regular expressions? I feel >> like such an idiot - being so strong in a programming language but knowing >> nothing about RE. > > I highly recommend reading the book "Mastering Regular Expressions," > which I believe is published by O'Reilly. It's a great reference and > helps peel the onion in terms of working through RE. They are a > language unto themselves. A fun brain exercise. > There is no real mention of python in this book, but the first edition is probably the best programming book I've ever read (excepting, perhaps Text Processing in Python by Mertz.) Well, come to think of it, check the latter book out. It has a great chapter on Python Regex. And its free to download. James -- http://mail.python.org/mailman/listinfo/python-list
Re: Regular Expressions
> That's a little harsh -- regexes have their place, together with pointer > arithmetic, bit manipulations, reverse polish notation and goto. The > problem is when people use them inappropriately e.g. using a regex when a > simple string.find will do. > > > A quote attributed variously to > > Tim Peters and Jamie Zawinski says "Some people, when confronted with a > > problem, think 'I know, I'll use regular expressions.' Now they have two > > problems." > > I believe that is correctly attributed to Jamie Zawinski. > > -- > Steven So as a newbie, I have to ask. I've played with the re module now for a while, I think regular expressions are super fun and useful. As far as them being a problem I found they can be tricky and sometimes the regex's I've devised do unexpected things...(which I can think of two instances where that unexpected thing was something that I had hoped to get into further down the line, yay for me!). So I guess I don't really understand why they are a "bad idea" to use. I don't know of any other way yet to parse specific data out of a text, html, or xml file without resorting to regular expressions. What other ways are there? -- http://mail.python.org/mailman/listinfo/python-list
Re: Regular Expressions
jwz> Some people, when confronted with a problem, think 'I know, I'll jwz> use regular expressions.' Now they have two problems. dbl> So as a newbie, I have to ask So I guess I don't really dbl> understand why they are a "bad idea" to use. Regular expressions are fine in their place, however, you can get carried away. For example: http://www.ex-parrot.com/~pdw/Mail-RFC822-Address.html Skip -- http://mail.python.org/mailman/listinfo/python-list
Re: Regular Expressions
En Sun, 11 Feb 2007 13:35:26 -0300, [EMAIL PROTECTED]
<[EMAIL PROTECTED]> escribió:
>> (Steven?)
>> That's a little harsh -- regexes have their place, together with pointer
>> arithmetic, bit manipulations, reverse polish notation and goto. The
>> problem is when people use them inappropriately e.g. using a regex when
>> a
>> simple string.find will do.
>
> So as a newbie, I have to ask. I've played with the re module now for
> a while, I think regular expressions are super fun and useful. As far
> as them being a problem I found they can be tricky and sometimes the
> regex's I've devised do unexpected things...(which I can think of two
> instances where that unexpected thing was something that I had hoped
> to get into further down the line, yay for me!). So I guess I don't
> really understand why they are a "bad idea" to use. I don't know of
> any other way yet to parse specific data out of a text, html, or xml
> file without resorting to regular expressions.
> What other ways are there?
For very simple things, it's easier/faster to use string methods like find
or split. By example, splitting "2007-02-11" into y,m,d parts:
y,m,d = date.split("-")
is a lot faster than matching "(\d+)-(\d+)-(\d+)"
On the other hand, complex tasks like parsing an HTML/XML document,
*can't* be done with a regexp alone; but people insist anyway, and then
complain when it doesn't work as expected, and ask how to "fix" the
regexp...
Good usage of regexps maybe goes in the middle.
--
Gabriel Genellina
--
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Re: Regular Expressions
On Feb 12, 3:35 am, "[EMAIL PROTECTED]" <[EMAIL PROTECTED]> wrote: > > That's a little harsh -- regexes have their place, together with pointer > > arithmetic, bit manipulations, reverse polish notation and goto. The > > problem is when people use them inappropriately e.g. using a regex when a > > simple string.find will do. > > > > A quote attributed variously to > > > Tim Peters and Jamie Zawinski says "Some people, when confronted with a > > > problem, think 'I know, I'll use regular expressions.' Now they have two > > > problems." > > > I believe that is correctly attributed to Jamie Zawinski. > > > -- > > Steven > > So as a newbie, I have to ask. I've played with the re module now for > a while, I think regular expressions are super fun and useful. As far > as them being a problem I found they can be tricky and sometimes the > regex's I've devised do unexpected things...(which I can think of two > instances where that unexpected thing was something that I had hoped > to get into further down the line, yay for me!). So I guess I don't > really understand why they are a "bad idea" to use. Regexes are not "bad". However people tend to overuse them, whether they are overkill (like Gabriel's date-splitting example) or underkill -- see your next sentence :-) > I don't know of > any other way yet to parse specific data out of a text, html, or xml > file without resorting to regular expressions. > What other ways are there? Text: Paul Maguire's pyparsing module (Google is your friend); read David Mertz's book on text processing with Python (free download, I believe); modules for specific data formats e.g. csv HTML: htmllib and HTMLParser (both in the Python library), BeautifulSoup (again GIYF) XML: xml.* in the Python library. ElementTree (recommended) is included in Python 2.5; use xml.etree.cElementTree. HTH, John -- http://mail.python.org/mailman/listinfo/python-list
Re: Regular Expressions
[EMAIL PROTECTED] wrote: >> That's a little harsh -- regexes have their place, together with pointer >> arithmetic, bit manipulations, reverse polish notation and goto. The >> problem is when people use them inappropriately e.g. using a regex when a >> simple string.find will do. >> >>> A quote attributed variously to >>> Tim Peters and Jamie Zawinski says "Some people, when confronted with a >>> problem, think 'I know, I'll use regular expressions.' Now they have two >>> problems." >> I believe that is correctly attributed to Jamie Zawinski. >> >> -- >> Steven > > So as a newbie, I have to ask. I've played with the re module now for > a while, I think regular expressions are super fun and useful. As far > as them being a problem I found they can be tricky and sometimes the > regex's I've devised do unexpected things...(which I can think of two > instances where that unexpected thing was something that I had hoped > to get into further down the line, yay for me!). So I guess I don't > really understand why they are a "bad idea" to use. I don't know of > any other way yet to parse specific data out of a text, html, or xml > file without resorting to regular expressions. > What other ways are there? > Re's aren't inherently bad. Just avoid using them as a hammer to the extent that all your problems look like nails. They wouldn't exist if there weren't problems it was appropriate to use them on. Just try to use simpler techniques first. For example, don't use re's to find out if a string starts with a specific substring when you could instead use the .startswith() string method. regards Steve -- Steve Holden +44 150 684 7255 +1 800 494 3119 Holden Web LLC/Ltd http://www.holdenweb.com Skype: holdenweb http://del.icio.us/steve.holden Blog of Note: http://holdenweb.blogspot.com See you at PyCon? http://us.pycon.org/TX2007 -- http://mail.python.org/mailman/listinfo/python-list
Re: Regular Expressions
HTML: htmllib and HTMLParser (both in the Python library), BeautifulSoup (again GIYF) XML: xml.* in the Python library. ElementTree (recommended) is included in Python 2.5; use xml.etree.cElementTree. The source of HTMLParser and xmllib use regular expressions for parsing out the data. htmllib calls sgmllib at the begining of it's code--sgmllib starts off with a bunch of regular expressions used to parse data. So the only real difference there I see is that someone saved me the work of writing them ;0). I haven't looked at the source for Beautiful Soup, though I have the sneaking suspicion that most processing of html/xml is all based on regex's. -- http://mail.python.org/mailman/listinfo/python-list
Re: Regular Expressions
On Feb 12, 9:20 pm, "[EMAIL PROTECTED]" <[EMAIL PROTECTED]> wrote: > HTML: htmllib and HTMLParser (both in the Python library), > BeautifulSoup (again GIYF) > > XML: xml.* in the Python library. ElementTree (recommended) is > included in Python 2.5; use xml.etree.cElementTree. > > The source of HTMLParser and xmllib use regular expressions for > parsing out the data. htmllib calls sgmllib at the begining of it's > code--sgmllib starts off with a bunch of regular expressions used to > parse data. So the only real difference there I see is that someone > saved me the work of writing them ;0). I haven't looked at the source > for Beautiful Soup, though I have the sneaking suspicion that most > processing of html/xml is all based on regex's. That's right. Those modules use regexes. You don't. You call functions & classes in the modules. Someone has written those modules and tested them and documented them and they've had a fair old thrashing by quite a few people over the years -- it may be the only difference in your way of thinking but it's quite a large difference from you opening up the re docs and getting stuck in single-handedly :-) -- http://mail.python.org/mailman/listinfo/python-list
Re: Regular Expressions
On 2007-02-10, Geoff Hill <[EMAIL PROTECTED]> wrote: > What's the way to go about learning Python's regular > expressions? I feel like such an idiot - being so strong in a > programming language but knowing nothing about RE. A great way to learn regular expressions is to implement them. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: Regular Expressions
dbl> The source of HTMLParser and xmllib use regular expressions for
dbl> parsing out the data. htmllib calls sgmllib at the begining of it's
dbl> code--sgmllib starts off with a bunch of regular expressions used
dbl> to parse data.
I am almost certain those modules use regular expressions for lexical
analysis (splitting the input byte stream into "words"), not for parsing
(extracting the structure of the "sentences").
If I have a simple expression:
(7 + 3.14) * CONST
that's just a stream of bytes, "(", "&", " ", "+", ... Lexical analysis
chunks that stream of bytes into the "words" of the language:
LPAREN (NUMBER, 7) PLUS (NUMBER, 3.14) RPAREN TIMES (IDENT, "CONST")
Parsing then constructs a higher level representation of that stream of
"words" (more commonly called tokens or lexemes). That representation is
application-dependent.
Regular expressions are ideal for lexical analysis. They are not-so-hot for
parsing unless the grammar of the language being parsed is *extremely*
simple.
Here are a couple much better expositions on the topics:
http://en.wikipedia.org/wiki/Lexical_analysis
http://en.wikipedia.org/wiki/Parsing
Skip
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Re: Regular Expressions
En Mon, 12 Feb 2007 07:20:11 -0300, [EMAIL PROTECTED] <[EMAIL PROTECTED]> escribió: > The source of HTMLParser and xmllib use regular expressions for > parsing out the data. htmllib calls sgmllib at the begining of it's > code--sgmllib starts off with a bunch of regular expressions used to > parse data. So the only real difference there I see is that someone > saved me the work of writing them ;0). I haven't looked at the source > for Beautiful Soup, though I have the sneaking suspicion that most > processing of html/xml is all based on regex's. You can build a parser for SGML/HTML/XML documents using regexps AND python code. You can't do that with regexps only. By example, suppose you work hard to build a correct regexp for matching an opening tag. You extract this from the document: "". Is it actually an tag? Maybe. But the text could be inside a comment. Or in a CDATA section. Or inside javascript code. Or... A regexp is good for recognizing tokens, and this can be used to build a parser. But regular expressions alone can't parse these kind of documents, just because their grammar is not regular. (Python re engine is stronger that "mathematical" regular expressions, in the sense that it can handle things like backreferences (?P=...) and lookahead (?=...) but anyway it can't handle HTML) -- Gabriel Genellina -- http://mail.python.org/mailman/listinfo/python-list
regular expressions use
hi everyone.
i would like to do some uri-decoding, which means to translate patterns
like "%2b/dhg-%3b %7E" into "+/dhg-; ~": in practice, if a sequence like
"%2b" is found, it should be translated into one character whose hex
ascii code is 2b.
i did this:
...
import re
import sys
modello = re.compile("%([0-9a-f][0-9a-f])", re.IGNORECASE)
def funzione(corrispondenza):
return chr(eval('0x' + corrispondenza.group(1)))
for riga in sys.stdin:
riga = modello.sub(funzione, riga)
sys.stdout.write(riga)
...
please comment it. can it be made easily or more compactly? i am a
python regexp novice.
bye
max
ps: i was trying to pythonate this kind of perl code:
$riga =~ s/%([A-Fa-f0-9][A-Fa-f0-9])/chr(hex($1))/ge;
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Concerning Regular Expressions
I've been reading a bunch of articles and tutorials on the net, but I cannot quite get ahold of the whole regular expression process. I have a list that contains about thirty strings, each in its own spot in the list. What I want to do is search the list, say it's called 'lines', for 'R0 -'. Thanks in advanced for any and all info that I recieve. -Tempo- -- http://mail.python.org/mailman/listinfo/python-list
tricky regular expressions
I'm trying to get the right syntax for my regular expression. The string I'm trying to parse is: # myString [USELESS DATA] Request: Play [USELESS DATA] Name: David Dude [USELESS DATA] Request: Next [USELESS DATA] Name: Ernesto Python User # Right now, I'm using the following code: pattern_Name= '''(?x) Title:\s+(.+) ''' names = re.findall(pattern_Name, myString) print names This captures all of the names, but I want an added requirement: Only capture names which are followed (not necessarily immediately) by "Request: Play" or "Request: Next". I guess the regular expression would look something like: '''(?x) ["Request: Play" OR "Request: Next"][intermediate data]Title:\s+(.+) ''' I didn't see any RE constructs like this in the docs, but I have a feeling it's possible. -- http://mail.python.org/mailman/listinfo/python-list
tricky regular expressions
So regular expressions have been good to me so far, but now my problem is a bit trickier. The string I'm getting data from looks like this: myString = [USELESS DATA] Request : Play [USELESS DATA] Title: Beethoven's 5th [USELESS DATA] Request : next [USELESS DATA] Title: song #2 . I'm using this code to search myString: pattern = '''(?x) Title:\s+(.+) ''' Titles = re.findall(pattern, myString) The problem is that I only want the "Titles" which are either: a) Followed by "Request : Play" b) Followed by "Request : next" I'm not sure if I should use RE's or some other mechanism. Thanks -- http://mail.python.org/mailman/listinfo/python-list
Re: Regular Expressions
escape chars are always a pain when making regex's. There is a section on it the Regex HOWTO http://www.amk.ca/python/howto/regex/regex.html#SECTION00042 -- http://mail.python.org/mailman/listinfo/python-list
Re: Regular Expressions
Ron wrote: > This is probably a repeated question, but try as I might I was unable > to find something similar in the archives. > > I'm trying to develop a regular expression for recognizing a simplified > C-Style string syntax. I need it to be able to handle escape sequences > of the form \x where x is any character including ". > > Here's what I'm trying: > > \"([^"\\]|(\\.))*\" > > When I try to get it to recognize something like: > >"I said, \"Hello!\"" > > It stops at the first quote after the \. Works for me: >>> print re.search(r'\"([^"\\]|(\\.))*\"', ... r'"I said \"Hello!\""').group(0) "I said \"Hello!\"" You can leave out the backslashes in fron of the first and last quotes in the regex, by the way, at least if you use ' instead of " to delimite it: >>> print re.search(r'"([^"\\]|(\\.))*"', ... r'"I said \"Hello!\""').group(0) "I said \"Hello!\"" -- If I have been able to see further, it was only because I stood on the shoulders of giants. -- Isaac Newton Roel Schroeven -- http://mail.python.org/mailman/listinfo/python-list
Re: Regular Expressions
david brochu jr wrote:
> I am trying to grab the following string out of a text file using
> regular expression (re module):
Why do you have to use a regular expression?
> "DcaVer"=dword:0640
Is all your other input pretty much identical in form? Specifically,
the number of interest is the last thing on the line, and always
preceded by a colon?
> What I need to do with that string is trim down " "DcaVer"=dword:" and
> convert the remaining number from hex to dec.
What does "trim down" mean? Do you need something out of the string, or
are you just discarding/ignoring it?
> I have been trying to figure this out for a while..I am fairly new so
> please any help would be greatly appreciated.
s = '"DcaVer"=dword:0640'
value = int(s.split(':')[-1], 16)
(In other words, split on colons, take the last field and, treating it
as a hex value, convert to an integer.)
-Peter
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Re: Regular Expressions
david brochu jr wrote:
> Hi,
>
> I am trying to grab the following string out of a text file using regular
> expression (re module):
>
> "DcaVer"=dword:0640
>
> What I need to do with that string is trim down " "DcaVer"=dword:" and
> convert the remaining number from hex to dec.
>
> I have been trying to figure this out for a while..I am fairly new so
> please any help would be greatly appreciated.
line = '"DcaVer"=dword:0640'
value = int(line.split(':')[1], 16)
Note that no regexes are needed.
Cheers.
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Tucson, AZ
USA
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Re: Regular Expressions
Pete,
Why do you have to use a regular _expression_?
I don't, I just though this was the easiest way.> "DcaVer"=dword:0640Is all your other input pretty much identical in form? Specifically,the number of interest is the last thing on the line, and always
preceded by a colon?
The other information is pretty much identical in form, yes. Exactally, all I am interested in is the number following the colon.
> What I need to do with that string is trim down " "DcaVer"=dword:" and> convert the remaining number from hex to dec.What does "trim down" mean? Do you need something out of the string, or
are you just discarding/ignoring it?
What I meant was I want to discard the "DcaVer"=dword: . All I am interested in is searching for "DcaVer, finding it, and then taking the numerical value found after the colon.
s = '"DcaVer"=dword:0640'value = int(s.split(':')[-1], 16)(In other words, split on colons, take the last field and, treating itas a hex value, convert to an integer.)
The only problem with this is DcaVer's value is not always going to be the same, so I need to search specially for DcaVer and then after finding it get the numerical value associated with it.
Thanks
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Re: Regular Expressions
> I am trying to grab the following string out of a text file using regular
> expression (re module):
While I'm all for using regexps when they're needed, are you
sure you need the overhead of regexps?
f = open("foo.txt", "r")
for line in f.readlines():
#if '"DcaVer"=dword:' in line:
if line.startswith('"DcaVer"=dword:'):
value = int(line.split(":", 1)[-1], 16)
print value
f.close()
If you absolutely must use a regexp,
import re
f = open("foo", "r")
r = re.compile(r'"DcaVer"=dword:([0-9a-fA-F]{7})')
for line in f.readlines():
m = r.match(line)
if m:
value = int(m.group(1), 16)
print value
f.close()
should do the trick for you. This assumes that each string
of hex digits has seven characters. Adjust accordingly.
-tim
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Re: Regular Expressions...
On Thu, Jan 8, 2009 at 8:54 AM, Ken D'Ambrosio wrote: > Hi, all. As a recovering Perl guy, I have to admit I don't quite "get" > the re module. For example, I'd like to do a few things (I'm going to use > phone numbers, 'cause that's what I'm currently dealing with): > 12345678900 -- How would I: > - Get just the area code? > - Get just the seven-digit number? > > In Perl, I'd so something like > m/^1(...)(...)/; > and then I'd have that stuff in $1 and $2, respectively. But the Python > stuff > simply isn't clicking for me. If anyone could supply concrete examples of > how to do the problem, above, that would be terrific. There is nothing so special or different about Python's re module than say over any other language's regular expression library or capabilities. You should be able to use pretty much the same things, however: 1. Why can't you just use ordinary string manipulation her e? One of Python's strengths is in string manipulation. Consider: >>> s = "1234567890" >>> area, number = s[:2], s[2:] >>> area '12' >>> number '34567890' cheers James -- http://mail.python.org/mailman/listinfo/python-list
Re: Regular Expressions...
Ken D'Ambrosio wrote: Hi, all. As a recovering Perl guy, I have to admit I don't quite "get" the re module. For example, I'd like to do a few things (I'm going to use phone numbers, 'cause that's what I'm currently dealing with): > 12345678900 -- How would I: > - Get just the area code? > - Get just the seven-digit number? In Perl, I'd so something like m/^1(...)(...)/; and then I'd have that stuff in $1 and $2, respectively. But the Python stuff simply isn't clicking for me. If anyone could supply concrete examples of how to do the problem, above, that would be terrific. Perl puts the captured text into variables as a side-effect, which, from the Python point of view, is undesirable 'magic'. The Python way is for the result to be returned like any normal function or method call: match = re.search(r"^1(...)(...)", phone_number) # match is now a match object if successful or None if unsuccessful if match: area_code = match.group(1) local_code = match.group(2) # or: # area_code, local_code = match.groups() No magic involved! (In this case simple string slicing would be simpler and faster.) -- http://mail.python.org/mailman/listinfo/python-list
Re: Regular Expressions...
Ken D'Ambrosio wrote: Hi, all. As a recovering Perl guy, [snip] In Perl, I'd so something like m/^1(...)(...)/; Indeed it seems you are recovering from an especially bad case. I recommend two doses of the python cookbook per day for one to two months. Report back here after your first cycle and we'll tell you how you are doing. I'm very optimistic about the prognosis. James -- http://mail.python.org/mailman/listinfo/python-list
Re: Regular Expressions...
On Thu, Jan 8, 2009 at 10:03 AM, James Stroud wrote: (...) > Indeed it seems you are recovering from an especially bad case. I recommend > two doses of the python cookbook per day for one to two months. Report back > here after your first cycle and we'll tell you how you are doing. I'm very > optimistic about the prognosis. 2nd opinion :) I highly recommend a strong dose of the Python Tutorial (1) followed by a recovery program of the Python Docs (2) cheers James 1. http://docs.python.org/tutorial/ 2. http://docs.python.org/ -- http://mail.python.org/mailman/listinfo/python-list
Re: Regular Expressions...
Ken D'Ambrosio: > But the Python stuff simply isn't clicking for me. For people coming from Perl that want to perform some string processing with Python I suggest to learn first array/string slices and string methods. And to try to use the regular expressions as little as possible. Bye, bearophile -- http://mail.python.org/mailman/listinfo/python-list
Re: Regular Expressions...
"Ken D'Ambrosio" writes:
> Hi, all. As a recovering Perl guy, I have to admit I don't quite "get"
> the re module. For example, I'd like to do a few things (I'm going to use
> phone numbers, 'cause that's what I'm currently dealing with):
> 12345678900 -- How would I:
> - Get just the area code?
> - Get just the seven-digit number?
>
> In Perl, I'd so something like
> m/^1(...)(...)/;
Wouldn't that be better as:
m/^1(\d{3})(\d{7})$/;
I'll assume that more-precise expression in what follows.
> and then I'd have the numbers in $1 and $2, respectively. But the Python
> stuff simply isn't clicking for me.
In general, where a set of data is likely to be iterated, the Pythonic
way to present it is via a single iterable (instead of, in your Perl
example, separate variables).
Then, for those (generally less frequent) cases where you do want the
separate items, you can bind them in a single statement:
(foo, bar, baz) = some_sequence
or
(foo, bar, baz) = (item for item in some_sequence)
e.g.:
>>> (foo, bar, baz) = [1, 2, 3]
>>> foo
1
>>> bar
2
>>> baz
3
So, the match returned by the various ‘re’ module match functions is
an object which allows access to the grouped matches as a sequence.
> If anyone could supply concrete examples of how to do the problem,
> above, that would be terrific.
Assuming the following:
>>> import re
>>> phone_number_regex = '^1(\d{3})(\d{7})$'
Trivial one-shot example:
>>> phone_number = '12345678900'
>>> (area_code, local_number) = re.match(phone_number_regex,
phone_number).groups()
>>> area_code
'234'
>>> local_number
'5678900'
More explicit example, showing the various steps and assuming you want
to re-use the various values in multiple statements:
>>> phone_number_pattern = re.compile(phone_number_regex)
>>> phone_number_pattern
<_sre.SRE_Pattern object at 0xf7f8c598>
>>> phone_number = '12345678900'
>>> phone_number_match = phone_number_pattern.match(phone_number)
>>> phone_number_match
<_sre.SRE_Match object at 0xf7f52338>
>>> (area_code, local_number) = phone_number_match.groups()
>>> area_code
'234'
>>> local_number
'5678900'
Python regular expressions also allow naming each group, for later
access to the matches via a dict:
>>> phone_number_regex = '^1(?P\d{3})(?P\d{7})'
>>> phone_number_pattern = re.compile(phone_number_regex)
>>> phone_number_match = phone_number_pattern.match(phone_number)
>>> phone_number_groups = phone_number_match.groupdict()
>>> phone_number_groups['area_code']
'234'
>>> phone_number_groups['local_number']
'5678900'
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`\that, lacking zero, they had no way to indicate successful |
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Re: Regular Expressions...
On 07Jan2009 19:51, Ken D'Ambrosio wrote:
| Hi, all. As a recovering Perl guy, I have to admit I don't quite "get"
| the re module. For example, I'd like to do a few things (I'm going to use
| phone numbers, 'cause that's what I'm currently dealing with):
| 12345678900 -- How would I:
| - Get just the area code?
| - Get just the seven-digit number?
|
| In Perl, I'd so something like
| m/^1(...)(...)/;
| and then I'd have the numbers in $1 and $2, respectively. But the Python
| stuff simply isn't clicking for me. If anyone could supply concrete
| examples of how to do the problem, above, that would be terrific.
I presume you're consulting this:
http://docs.python.org/library/re.html#module-re
Something like this (untested):
import re
phone = '12345678900'
num_re = re.compile('^1(...)(...)')
num_re is now a regular expression object:
http://docs.python.org/library/re.html#regular-expression-objects
much as you get from a "precompiled" perl regular expression.
m = num_re.match(phone)
m is now the result of a match against the phone number:
http://docs.python.org/library/re.html#id1
m.group(0) is what was matched by the whole expression. m.group(1) is perl's
$1, m.group(2) is $2 etc.
For example:
area_code = m.group(1)
There is also an expand() method that accepts \1, \2 etc in its
template. For direct substitutions (as in perl's s/this/that/) there is
the regular expression object sub() method.
It's a bit more broken out than you normally get in perl, but the pieces
are all there.
Cheers,
--
Cameron Simpson DoD#743
http://www.cskk.ezoshosting.com/cs/
Teamwork is essential. It lets you blame someone else.
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Re: Regular Expressions...
In article , Ken D'Ambrosio wrote: > >Hi, all. As a recovering Perl guy, I have to admit I don't quite "get" >the re module. Refer to the following every time you want to use regexes in Python: 'Some people, when confronted with a problem, think "I know, I'll use regular expressions." Now they have two problems.' --Jamie Zawinski, comp.emacs.xemacs, 8/1997 Although there are times when regexes are your best option, Python has many other good options for processing strings, and your code readability will usually increase if you try one of them first. -- Aahz (a...@pythoncraft.com) <*> http://www.pythoncraft.com/ Weinberg's Second Law: If builders built buildings the way programmers wrote programs, then the first woodpecker that came along would destroy civilization. -- http://mail.python.org/mailman/listinfo/python-list
regular expressions ... slow
Hi, Is anobody aware of this post: http://swtch.com/~rsc/regexp/regexp1.html ? Are there any plans to speed up Pythons regular expression module ? Or is the example in this artricle too far from reality ??? Greetings, Uwe -- http://mail.python.org/mailman/listinfo/python-list
Regular expressions question
Hello folks ,
I trying to match a pattern in a string , i am new in using re .This is what
is happening
When i do this
p = re.compile('(\[&&NHX:)')
>>> m = p.match("[&&NHX:C=0.195.0]")
>>> print m
<_sre.SRE_Match object at 0x013FE1E0>
--- thus i am able to find the match
but when i use the string
m = p.match("-bin-ulockmgr_server:0.99[&&NHX:")
>>> print m
None
-i am not able to find the match .
Can someone help me here.
Thanks
Aditya
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Unicode Regular Expressions
Hi, I'm writing a program that requires specifically Unicode regular expressions http://unicode.org/reports/tr18/ to be loaded in from an external file and then interpreted against the data. if I use Python Regular expressions is there a flag I can set to specify that the regular expressions that are loaded from the file conform to Unicode regular expressions. What problems can be expected using Unicode Regex with Python, is there a library I should be using? Cheers, Bryan Rasmussen -- http://mail.python.org/mailman/listinfo/python-list
Re: regular expressions
On Nov 6, 4:49 pm, [EMAIL PROTECTED] wrote: > hi i am looking for pattern in regular expreesion that replaces > anything starting with and betweeen http:// until / > likehttp://www.start.com/startservice/yellow/fdhttp://helo/abcdwill > be replaced as > p/startservice/yellow/ fdp/abcd What have you come up with so far? Have you looked at the 're' module? -- Paul Hankin -- http://mail.python.org/mailman/listinfo/python-list
Re: regular expressions
On Tue, Nov 06, 2007 at 08:49:33AM -0800, [EMAIL PROTECTED] wrote regarding regular expressions: > > hi i am looking for pattern in regular expreesion that replaces > anything starting with and betweeen http:// until / > like http://www.start.com/startservice/yellow/ fdhttp://helo/abcd will > be replaced as > p/startservice/yellow/ fdp/abcd > You don't need regular expressions to do that. Look into the methods that strings have. Look at slicing. Look at len. Keep your code readable for future generations. Py>>> help(str) Py>>> dir(str) Py>>> help(str.startswith) Cheers, Cliff -- http://mail.python.org/mailman/listinfo/python-list
Re: regular expressions
On Nov 6, 11:07 am, "J. Clifford Dyer" <[EMAIL PROTECTED]> wrote:
> On Tue, Nov 06, 2007 at 08:49:33AM -0800, [EMAIL PROTECTED] wrote regarding
> regular expressions:
>
>
>
> > hi i am looking for pattern in regular expreesion that replaces
> > anything starting with and betweeen http:// until /
> > likehttp://www.start.com/startservice/yellow/fdhttp://helo/abcdwill
> > be replaced as
> > p/startservice/yellow/ fdp/abcd
>
> You don't need regular expressions to do that. Look into the methods that
> strings have. Look at slicing. Look at len. Keep your code readable for
> future generations.
>
> Py>>> help(str)
> Py>>> dir(str)
> Py>>> help(str.startswith)
>
> Cheers,
> Cliff
Look again at the sample input. Some of the OP's replacement targets
are not at the beginning of a word, so str.startswith wont be much
help.
Here are 2 solutions, one using re, one using pyparsing.
-- Paul
instr = """
anything starting with and betweeen "http://"; until "/"
like http://www.start.com/startservice/yellow/ fdhttp://helo/abcd
will
be replaced as
"""
REPLACE_STRING = "p"
# an re solution
import re
print re.sub("http://[^/]*";, REPLACE_STRING, instr)
# a pyparsing solution - with handling of target strings inside quotes
from pyparsing import SkipTo, replaceWith, quotedString
replPattern = "http://"; + SkipTo("/")
replPattern.setParseAction( replaceWith(REPLACE_STRING) )
replPattern.ignore(quotedString)
print replPattern.transformString(instr)
Prints:
anything starting with and betweeen "p/"
like p/startservice/yellow/ fdp/abcd will
be replaced as
anything starting with and betweeen "http://"; until "/"
like p/startservice/yellow/ fdp/abcd will
be replaced as
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Re: regular expressions
Paul McGuire wrote:
> On Nov 6, 11:07 am, "J. Clifford Dyer" <[EMAIL PROTECTED]> wrote:
>
>> On Tue, Nov 06, 2007 at 08:49:33AM -0800, [EMAIL PROTECTED] wrote regarding
>> regular expressions:
>>
>>
>>
>>
>>> hi i am looking for pattern in regular expreesion that replaces
>>> anything starting with and betweeen http:// until /
>>> likehttp://www.start.com/startservice/yellow/fdhttp://helo/abcdwill
>>> be replaced as
>>> p/startservice/yellow/ fdp/abcd
>>>
>> You don't need regular expressions to do that. Look into the methods that
>> strings have. Look at slicing. Look at len. Keep your code readable for
>> future generations.
>>
>> Py>>> help(str)
>> Py>>> dir(str)
>> Py>>> help(str.startswith)
>>
>> Cheers,
>> Cliff
>>
>
> Look again at the sample input. Some of the OP's replacement targets
> are not at the beginning of a word, so str.startswith wont be much
> help.
>
> Here are 2 solutions, one using re, one using pyparsing.
>
> -- Paul
>
>
> instr = """
> anything starting with and betweeen "http://"; until "/"
> like http://www.start.com/startservice/yellow/ fdhttp://helo/abcd
> will
> be replaced as
> """
>
> REPLACE_STRING = "p"
>
> # an re solution
> import re
> print re.sub("http://[^/]*";, REPLACE_STRING, instr)
>
>
> # a pyparsing solution - with handling of target strings inside quotes
> from pyparsing import SkipTo, replaceWith, quotedString
>
> replPattern = "http://"; + SkipTo("/")
> replPattern.setParseAction( replaceWith(REPLACE_STRING) )
> replPattern.ignore(quotedString)
>
> print replPattern.transformString(instr)
>
>
> Prints:
>
> anything starting with and betweeen "p/"
> like p/startservice/yellow/ fdp/abcd will
> be replaced as
>
>
> anything starting with and betweeen "http://"; until "/"
> like p/startservice/yellow/ fdp/abcd will
> be replaced as
>
>
Interesting. In my email clients, they do show up at the beginning of
words (thunderbird and mutt), but in your reply they aren't. I wonder
if there's some funky unicode space that your computer isn't
rendering Or something on my end. There were definitely spaces in
his email as it appears on my computer.
But if there aren't, s.startswith() is clearly not the way to go.
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Re: regular expressions.
Atul. wrote: > I have been playing around with REs and could not get the following > code to run. > > import re > vowel = r'[aeiou]' > re.findall(vowel, r"vowel") > > anything wrong I have done? Yes. You didn't paste the traceback into your message. >>> import re >>> vowel = r'[aeiou]' >>> re.findall(vowel, r"vowel") ['o', 'e'] It works as expected here. Peter -- http://mail.python.org/mailman/listinfo/python-list
Re: regular expressions.
> Yes. You didn't paste the traceback into your message. > > >>> import re > >>> vowel = r'[aeiou]' > >>> re.findall(vowel, r"vowel") > > ['o', 'e'] > > It works as expected here. > > Peter When I key this input in IDLE it works but when I try to run the module it wont work. -- http://mail.python.org/mailman/listinfo/python-list
Re: regular expressions.
Use the print statement: import re vowel = r'[aeiou]' print re.findall(vowel, r"vowel") Alexey On Fri, Aug 8, 2008 at 2:17 PM, Atul. <[EMAIL PROTECTED]> wrote: > > > Yes. You didn't paste the traceback into your message. > > > > >>> import re > > >>> vowel = r'[aeiou]' > > >>> re.findall(vowel, r"vowel") > > > > ['o', 'e'] > > > > It works as expected here. > > > > Peter > > When I key this input in IDLE it works but when I try to run the > module it wont work. > -- > http://mail.python.org/mailman/listinfo/python-list > -- http://mail.python.org/mailman/listinfo/python-list
Re: regular expressions.
Atul. wrote: > >> Yes. You didn't paste the traceback into your message. >> >> >>> import re >> >>> vowel = r'[aeiou]' >> >>> re.findall(vowel, r"vowel") >> >> ['o', 'e'] >> >> It works as expected here. >> >> Peter > > When I key this input in IDLE it works but when I try to run the > module it wont work. What's the name of your script? What happens when you run it? Does it print a traceback? If so, what does it say? Please cut and paste, don't paraphrase. Peter -- http://mail.python.org/mailman/listinfo/python-list
Re: regular expressions.
On Aug 8, 4:22 pm, Peter Otten <[EMAIL PROTECTED]> wrote: > Atul. wrote: > > >> Yes. You didn't paste the traceback into your message. > > >> >>> import re > >> >>> vowel = r'[aeiou]' > >> >>> re.findall(vowel, r"vowel") > > >> ['o', 'e'] > > >> It works as expected here. > > >> Peter > > > When I key this input in IDLE it works but when I try to run the > > module it wont work. > > What's the name of your script? What happens when you run it? Does it print > a traceback? If so, what does it say? Please cut and paste, don't > paraphrase. > > Peter This is something get when I run it like below. it does not print any output. [EMAIL PROTECTED]:~/Work/work/programs$ python fourth.py [EMAIL PROTECTED]:~/Work/work/programs$ -- http://mail.python.org/mailman/listinfo/python-list
Re: regular expressions.
On Aug 8, 4:33 pm, "Atul." <[EMAIL PROTECTED]> wrote: > On Aug 8, 4:22 pm, Peter Otten <[EMAIL PROTECTED]> wrote: > > > > > Atul. wrote: > > > >> Yes. You didn't paste the traceback into your message. > > > >> >>> import re > > >> >>> vowel = r'[aeiou]' > > >> >>> re.findall(vowel, r"vowel") > > > >> ['o', 'e'] > > > >> It works as expected here. > > > >> Peter > > > > When I key this input in IDLE it works but when I try to run the > > > module it wont work. > > > What's the name of your script? What happens when you run it? Does it print > > a traceback? If so, what does it say? Please cut and paste, don't > > paraphrase. > > > Peter > > This is something get when I run it like below. it does not print any > output. > > [EMAIL PROTECTED]:~/Work/work/programs$ python fourth.py > [EMAIL PROTECTED]:~/Work/work/programs$ ok I get it thats coz, I dont print it. right? when I print it does she it. -- http://mail.python.org/mailman/listinfo/python-list
Re: regular expressions.
Atul. schrieb: On Aug 8, 4:33 pm, "Atul." <[EMAIL PROTECTED]> wrote: On Aug 8, 4:22 pm, Peter Otten <[EMAIL PROTECTED]> wrote: Atul. wrote: Yes. You didn't paste the traceback into your message. import re vowel = r'[aeiou]' re.findall(vowel, r"vowel") ['o', 'e'] It works as expected here. Peter When I key this input in IDLE it works but when I try to run the module it wont work. What's the name of your script? What happens when you run it? Does it print a traceback? If so, what does it say? Please cut and paste, don't paraphrase. Peter This is something get when I run it like below. it does not print any output. [EMAIL PROTECTED]:~/Work/work/programs$ python fourth.py [EMAIL PROTECTED]:~/Work/work/programs$ ok I get it thats coz, I dont print it. right? when I print it does she it. Yes. Diez -- http://mail.python.org/mailman/listinfo/python-list
Re: regular expressions.
Atul. wrote: > On Aug 8, 4:33 pm, "Atul." <[EMAIL PROTECTED]> wrote: >> On Aug 8, 4:22 pm, Peter Otten <[EMAIL PROTECTED]> wrote: >> >> >> >> > Atul. wrote: >> >> > >> Yes. You didn't paste the traceback into your message. >> >> > >> >>> import re >> > >> >>> vowel = r'[aeiou]' >> > >> >>> re.findall(vowel, r"vowel") >> >> > >> ['o', 'e'] >> >> > >> It works as expected here. >> >> > >> Peter >> >> > > When I key this input in IDLE it works but when I try to run the >> > > module it wont work. >> >> > What's the name of your script? What happens when you run it? Does it >> > print a traceback? If so, what does it say? Please cut and paste, don't >> > paraphrase. >> >> > Peter >> >> This is something get when I run it like below. it does not print any >> output. >> >> [EMAIL PROTECTED]:~/Work/work/programs$ python fourth.py >> [EMAIL PROTECTED]:~/Work/work/programs$ > > ok I get it thats coz, I dont print it. right? when I print it does > she it. Heureka! -- http://mail.python.org/mailman/listinfo/python-list
Re: regular expressions.
The same file when I use with the following does not work. import re vowel = r'[u"\u093e"u"\u093f"u"\u0940"u"\u0941"u"\u0942"u"\u0943"u"\u0944"u"\u0945"u"\u0946"u"\u0947"u"\u0948"u"\u0949"u"\u094a"u"\u094b"u"\u094c"]' print re.findall(vowel, u"\u092f\u093e\u0902\u091a\u094d\u092f\u093e", re.UNICODE) [EMAIL PROTECTED]:~/Work/work/programs$ python fourth.py [] [EMAIL PROTECTED]:~/Work/work/programs$ is this the way to use Unicode in REs? Regards, Atul. -- http://mail.python.org/mailman/listinfo/python-list
Re: regular expressions.
Atul. wrote: > The same file when I use with the following does not work. > > import re > vowel = > r'[u"\u093e"u"\u093f"u"\u0940"u"\u0941"u"\u0942"u"\u0943"u"\u0944"u"\u0945"u"\u0946"u"\u0947"u"\u0948"u"\u0949"u"\u094a"u"\u094b"u"\u094c"]' > print re.findall(vowel, u"\u092f\u093e\u0902\u091a\u094d\u092f\u093e", > re.UNICODE) > > > > [EMAIL PROTECTED]:~/Work/work/programs$ python fourth.py > [] > [EMAIL PROTECTED]:~/Work/work/programs$ > > > is this the way to use Unicode in REs? No, u"..." is part of the string, not the character. The regex becomes # untested vowel = u'[\u093e\u093f\u0940\u0941\u0942\u0943\u0944\u0945\u0946\u0947\u0948\u0949\u094a\u094b\u094c]' Peter -- http://mail.python.org/mailman/listinfo/python-list
Re: regular expressions.
"Atul." <[EMAIL PROTECTED]> writes: > the following does not work. > > import re > vowel = > r'[u"\u093e"u"\u093f"u"\u0940"u"\u0941"u"\u0942"u"\u0943"u"\u0944"u"\u0945"u"\u0946"u"\u0947"u"\u0948"u"\u0949"u"\u094a"u"\u094b"u"\u094c"]' Unfortunately you cannot embed arbitrary Python string constants (u"...") in regular expressions. What does work is something like: >>> vowel = >>> u'[\u093e\u093f\u0940\u0941\u0942\u0943\u0944\u0945\u0946\u0947\u0948\u0949\u094a\u094b\u094c]' >>> re.findall(vowel, u"\u092f\u093e\u0902\u091a\u094d\u092f\u093e") [u'\u093e', u'\u093e'] -- http://mail.python.org/mailman/listinfo/python-list
Re: Regular expressions
On 2015-11-03 01:09, Seymore4Head wrote: How do I make a regular expression that returns true if the end of the line is an asterisk To match an asterisk: \* To match the end of a line: $ To match an asterisk at the end of a line: \*$ -- https://mail.python.org/mailman/listinfo/python-list
Re: Regular expressions
On 2015-11-02 20:09, Seymore4Head wrote: > How do I make a regular expression that returns true if the end of > the line is an asterisk Why use a regular expression? if line[-1] == '*': yep(line) else: nope(line) -tkc -- https://mail.python.org/mailman/listinfo/python-list
Re: Regular expressions
On Mon, 2 Nov 2015 20:42:37 -0600, Tim Chase wrote: >On 2015-11-02 20:09, Seymore4Head wrote: >> How do I make a regular expression that returns true if the end of >> the line is an asterisk > >Why use a regular expression? > > if line[-1] == '*': >yep(line) > else: >nope(line) > >-tkc > > Because that is the part of Python I am trying to learn at the moment. Thanks -- https://mail.python.org/mailman/listinfo/python-list
Re: Regular expressions
On Tue, 3 Nov 2015 01:19:34 +, MRAB wrote: >On 2015-11-03 01:09, Seymore4Head wrote: >> How do I make a regular expression that returns true if the end of the >> line is an asterisk >> >To match an asterisk: \* > >To match the end of a line: $ > >To match an asterisk at the end of a line: \*$ Thanks -- https://mail.python.org/mailman/listinfo/python-list
Re: Regular expressions
On 11/02/2015 07:42 PM, Tim Chase wrote: > On 2015-11-02 20:09, Seymore4Head wrote: >> How do I make a regular expression that returns true if the end of >> the line is an asterisk > > Why use a regular expression? > > if line[-1] == '*': > yep(line) > else: > nope(line) Indeed, sometimes Jamie Zawinski's is often quite appropriate: Some people, when confronted with a problem, think "I know, I'll use regular expressions." Now they have two problems. -- https://mail.python.org/mailman/listinfo/python-list
Re: Regular expressions
On Mon, Nov 2, 2015 at 10:17 PM, Seymore4Head wrote: > On Mon, 2 Nov 2015 20:42:37 -0600, Tim Chase > wrote: > > >On 2015-11-02 20:09, Seymore4Head wrote: > >> How do I make a regular expression that returns true if the end of > >> the line is an asterisk > > > >Why use a regular expression? > > > > if line[-1] == '*': > >yep(line) > > else: > >nope(line) > > > >-tkc > > > > > Because that is the part of Python I am trying to learn at the moment. > Thanks > -- > https://mail.python.org/mailman/listinfo/python-list > My completely unsolicited advice is that regular expressions shouldn't be very high on the list of things to learn. They are very useful, and very tricky and prone many problems that can and should be learned to be resolved with much simpler methods. If you really want to learn regular expressions, that's great but the problem you posed is not one for which they are the best solution. Remember simpler is better than complex. -- Joel Goldstick http://joelgoldstick.com/stats/birthdays -- https://mail.python.org/mailman/listinfo/python-list
Re: Regular expressions
On 11/02/2015 08:51 PM, Michael Torrie wrote: >[...] > Indeed, sometimes Jamie Zawinski's is often quite appropriate: > > Some people, when confronted with a problem, think "I know, I'll use > regular expressions." Now they have two problems. Or its sometimes heard paraphrase: Some people, when confronted with a problem, think "I know, I'll use Python." Now they have two problems The point being it's a cute and memorable aphorism but not very meaningful because it can be applied to anything one wishes to denigrate. Of course there are people who misuse regexes. But I am quite sure, especially in the Python community, there are just as many who fail to use them when they are appropriate which is just as bad. -- https://mail.python.org/mailman/listinfo/python-list
Re: Regular expressions
On Monday, November 2, 2015 at 8:58:45 PM UTC-7, Joel Goldstick wrote: > On Mon, Nov 2, 2015 at 10:17 PM, Seymore4Head > wrote: > > > On Mon, 2 Nov 2015 20:42:37 -0600, Tim Chase > > wrote: > > > > >On 2015-11-02 20:09, Seymore4Head wrote: > > >> How do I make a regular expression that returns true if the end of > > >> the line is an asterisk > > > > > >Why use a regular expression? > > > > > > if line[-1] == '*': > > >yep(line) > > > else: > > >nope(line) > > > > > >-tkc > > > > > > > > Because that is the part of Python I am trying to learn at the moment. > > Thanks > > -- > > https://mail.python.org/mailman/listinfo/python-list > > > > My completely unsolicited advice is that regular expressions shouldn't be > very high on the list of things to learn. They are very useful, and very > tricky and prone many problems that can and should be learned to be > resolved with much simpler methods. If you really want to learn regular > expressions, that's great but the problem you posed is not one for which > they are the best solution. Remember simpler is better than complex. Regular expressions should be learned by every programmer or by anyone who wants to use computers as a tool. They are a fundamental part of computer science and are used in all sorts of matching and searching from compilers down to your work-a-day text editor. Not knowing how to use them is like an auto mechanic not knowing how to use a socket wrench. -- https://mail.python.org/mailman/listinfo/python-list
Re: Regular expressions
On 11/02/2015 09:23 PM, rurpy--- via Python-list wrote: > On 11/02/2015 08:51 PM, Michael Torrie wrote: >> [...] >> Indeed, sometimes Jamie Zawinski's is often quite appropriate: >> >> Some people, when confronted with a problem, think "I know, I'll use >> regular expressions." Now they have two problems. > > Or its sometimes heard paraphrase: > Some people, when confronted with a problem, think "I know, I'll use > Python." Now they have two problems > The point being it's a cute and memorable aphorism but not very meaningful > because it can be applied to anything one wishes to denigrate. > > Of course there are people who misuse regexes. But I am quite sure, > especially in the Python community, there are just as many who fail to > use them when they are appropriate which is just as bad. Judging by a few posts on the list lately, I'd say it is highly relevant to Python itself. Too many people have only a vague notion of a problem they'd like to solve and although they don't really understand the problem, they've heard Python is a good language to learn, so they ask how they can solve that problem with Python. Now, this certainly can work for a person who's already experienced in several languages and who already understands the problem. For others, it's very much now two intractable problems. -- https://mail.python.org/mailman/listinfo/python-list
Re: Regular expressions
On 11/02/2015 09:23 PM, rurpy--- via Python-list wrote: >> My completely unsolicited advice is that regular expressions shouldn't be >> very high on the list of things to learn. They are very useful, and very >> tricky and prone many problems that can and should be learned to be >> resolved with much simpler methods. If you really want to learn regular >> expressions, that's great but the problem you posed is not one for which >> they are the best solution. Remember simpler is better than complex. > > Regular expressions should be learned by every programmer or by anyone > who wants to use computers as a tool. They are a fundamental part of > computer science and are used in all sorts of matching and searching > from compilers down to your work-a-day text editor. > > Not knowing how to use them is like an auto mechanic not knowing how to > use a socket wrench. Not quite. Core language concepts like ifs, loops, functions, variables, slicing, etc are the socket wrenches of the programmer's toolbox. Regexs are like an electric impact socket wrench. You can do the same work without it, but in many cases it's slower. But you have to learn the other hand tools first in order to really use the electric driver properly (understanding torques, direction of threads, etc), lest you wonder why you're breaking off so many bolts with the torque of the impact drive. -- https://mail.python.org/mailman/listinfo/python-list
Re: Regular expressions
On Tue, 3 Nov 2015 03:23 pm, ru...@yahoo.com wrote: > Regular expressions should be learned by every programmer or by anyone > who wants to use computers as a tool. They are a fundamental part of > computer science and are used in all sorts of matching and searching > from compilers down to your work-a-day text editor. You are absolutely right. If only regular expressions weren't such an overly-terse, cryptic mini-language, with all but no debugging capabilities, they would be great. If only there wasn't an extensive culture of regular expression abuse within programming communities, they would be fine. All technologies are open to abuse. But we don't say: Some people, when confronted with a problem, think "I know, I'll use arithmetic." Now they have two problems. because abuse of arithmetic is rare. It's hard to misuse it, and while arithmetic can be complicated, it's rare for programmers to abuse it. But the same cannot be said for regexes -- they are regularly misused, abused, and down-right hard to use right even when you have a good reason for using them: http://www.thedailywtf.com/articles/Irregular_Expression http://blog.codinghorror.com/regex-use-vs-regex-abuse/ http://psung.blogspot.com.au/2008/01/wonderful-abuse-of-regular-expressions.html If there is one person who has done more to create a regex culture, it is Larry Wall, inventor of Perl. Even Larry Wall says that regexes are overused and their syntax is harmful, and he has recreated them for Perl 6: http://www.perl.com/pub/2002/06/04/apo5.html Oh, and the icing on the cake, regexes can be a security vulnerability too: https://www.owasp.org/index.php/Regular_expression_Denial_of_Service_-_ReDoS -- Steven -- https://mail.python.org/mailman/listinfo/python-list
Re: Regular expressions
On Tue, Nov 3, 2015 at 7:15 AM, Steven D'Aprano wrote: > On Tue, 3 Nov 2015 03:23 pm, ru...@yahoo.com wrote: > > > Regular expressions should be learned by every programmer or by anyone > > who wants to use computers as a tool. They are a fundamental part of > > computer science and are used in all sorts of matching and searching > > from compilers down to your work-a-day text editor. > > You are absolutely right. > > If only regular expressions weren't such an overly-terse, cryptic > mini-language, with all but no debugging capabilities, they would be great. > > If only there wasn't an extensive culture of regular expression abuse > within > programming communities, they would be fine. > > All technologies are open to abuse. But we don't say: > > Some people, when confronted with a problem, think "I know, I'll use > arithmetic." Now they have two problems. > > because abuse of arithmetic is rare. It's hard to misuse it, and while > arithmetic can be complicated, it's rare for programmers to abuse it. But > the same cannot be said for regexes -- they are regularly misused, abused, > and down-right hard to use right even when you have a good reason for using > them: > > http://www.thedailywtf.com/articles/Irregular_Expression > > http://blog.codinghorror.com/regex-use-vs-regex-abuse/ > > > http://psung.blogspot.com.au/2008/01/wonderful-abuse-of-regular-expressions.html > > > If there is one person who has done more to create a regex culture, it is > Larry Wall, inventor of Perl. Even Larry Wall says that regexes are > overused and their syntax is harmful, and he has recreated them for Perl 6: > > http://www.perl.com/pub/2002/06/04/apo5.html > > Oh, and the icing on the cake, regexes can be a security vulnerability too: > > > https://www.owasp.org/index.php/Regular_expression_Denial_of_Service_-_ReDoS > > > > -- > Steven > > -- > https://mail.python.org/mailman/listinfo/python-list > +1 I agree that regex is an entirely necessary part of a programmers toolkit, but dear god some people need to be taught restraint. The majority of people I talk about regex to have no idea when and where it shouldn't be used. As an example part of my job is bringing our legacy Python code into the modern day, and one of the largest roadblocks is the amount of regex used. Some is necessary. Some can be replaced by an `if word in str` or something similarly basic. Some spans hundreds of lines and causes acute alopecia. Just yesterday I found a colleague trying to parse HTML with regex. So yes, teach regex, but teach it after the basics, and please emphasise when it is appropriate to use it. Yes I am bitter. - Nick. -- https://mail.python.org/mailman/listinfo/python-list
Re: Regular expressions
Michael Torrie wrote:
> On 11/02/2015 07:42 PM, Tim Chase wrote:
>> On 2015-11-02 20:09, Seymore4Head wrote:
>>> How do I make a regular expression that returns true if the end of
>>> the line is an asterisk
>>
>> Why use a regular expression?
>>
>> if line[-1] == '*':
>> yep(line)
>> else:
>> nope(line)
>
> Indeed, sometimes Jamie Zawinski's is often quite appropriate:
>
> Some people, when confronted with a problem, think "I know, I'll use
> regular expressions." Now they have two problems.
Incidentally the code example has two "problems", too.
- What about the empty string?
- What about lines with a trailing "\n", i. e. as they are usually delivered
when iterating over a file?
Below is a comparison of some of your options. The "one obvious way"
line.rstrip("\n").endswith("*") is not included ;)
$ cat starry_table.py
import re
def show_table(data, header):
rows = [header]
rows.extend([str(c) for c in row] for row in data)
widths = [max(len(row[i]) for row in rows) for i in range(len(header))]
template = " ".join("{:%d}" % w for w in widths)
for row in rows:
print(template.format(*row))
def compare(sample_lines):
for line in sample_lines:
got_re = bool(re.compile("\*$").search(line))
got_re_M = bool(re.compile("\*$", re.M).search(line))
got_endswith = line.endswith("*")
got_endswith2 = line.endswith(("*", "*\n"))
got_substring = line[-1:] == "*"
try:
got_char = line[-1] == "*"
except IndexError:
got_char = "#exception"
results = (
got_re, got_re_M,
got_endswith, got_endswith2,
got_substring, got_char)
yield (
["", "X"][len(set(results)) > 1],
repr(line)) + results
SAMPLE = ["", "\n", "foo\n", "*\n", "*", "foo*", "foo*\n", "foo*\nbar"]
HEADER = [
"", "line", "regex", "re.M",
"endswith", 'endswith(("*", "*\\n"))',
"substring", "char"]
if __name__ == "__main__":
show_table(compare(SAMPLE), HEADER)
$ python3 starry_table.py
line regex re.M endswith endswith(("*", "*\n")) substring char
X '' False False False False False
#exception
'\n' False False False False False
False
'foo\n' False False False False False
False
X '*\n'True True False TrueFalse
False
'*' True True True TrueTrue True
'foo*' True True True TrueTrue True
X 'foo*\n' True True False TrueFalse
False
X 'foo*\nbar' False True False False False
False
--
https://mail.python.org/mailman/listinfo/python-list
Re: Regular expressions
On 2015-11-03 10:25, Peter Otten wrote: > >>> How do I make a regular expression that returns true if the end > >>> of the line is an asterisk > >> > >> Why use a regular expression? > >> > >> if line[-1] == '*': > >> yep(line) > >> else: > >> nope(line) > > Incidentally the code example has two "problems", too. > > - What about the empty string? Good catch: .endswith() works better. > - What about lines with a trailing "\n", i. e. as they are usually > delivered when iterating over a file? Then your string *doesn't* end with a "*", but rather with a newline. ;-) Though according to the OP's specs, the following function would work too: def ends_in_asterisk(s): return True It *does* return True if the line ends in an asterisk (no requirement to make the function return False under any other conditions). -tkc -- https://mail.python.org/mailman/listinfo/python-list
Re: Regular expressions
On Mon, 02 Nov 2015 22:17:49 -0500, Seymore4Head wrote:
> On Mon, 2 Nov 2015 20:42:37 -0600, Tim Chase
> wrote:
>
>>On 2015-11-02 20:09, Seymore4Head wrote:
>>> How do I make a regular expression that returns true if the end of the
>>> line is an asterisk
>>Why use a regular expression?
> Because that is the part of Python I am trying to learn at the moment.
The most important thing to learn about regular expressions is when to
use them and when not to use them.
Returning true if the last character in a string is an asterisk is almost
certainly a brilliant example of when not to use a regular expression.
Here are some timings I tested:
#!/usr/bin/python
import re
import timeit
patt = re.compile("\*$")
start_time = timeit.default_timer()
for i in range(100):
x = re.match("\*$", "test 1")
elapsed = timeit.default_timer() - start_time
print "re, false", elapsed
start_time = timeit.default_timer()
for i in range(100):
x = re.match("\*$", "test *")
elapsed = timeit.default_timer() - start_time
print "re, true", elapsed
start_time = timeit.default_timer()
for i in range(100):
x = patt.match("test 1")
elapsed = timeit.default_timer() - start_time
print "compiled re, false", elapsed
start_time = timeit.default_timer()
for i in range(100):
x = patt.match("test *")
elapsed = timeit.default_timer() - start_time
print "compiled re, true", elapsed
start_time = timeit.default_timer()
for i in range(100):
x = "test 1"[-1] == "*"
elapsed = timeit.default_timer() - start_time
print "char compare, false", elapsed
start_time = timeit.default_timer()
for i in range(100):
x = "test *"[-1] == "*"
elapsed = timeit.default_timer() - start_time
print "char compare, true", elapsed
RESULTS:
re, false 2.4701731205
re, true 2.42048001289
compiled re, false 0.875837087631
compiled re, true 0.876382112503
char compare, false 0.26283121109
char compare, true 0.263465881348
The compiled re is about 3 times as fast as the uncompiled re. The
character comparison is about 3 times as fast as the compiled re.
--
Denis McMahon, denismfmcma...@gmail.com
--
https://mail.python.org/mailman/listinfo/python-list
Re: Regular expressions
Tim Chase wrote: > On 2015-11-03 10:25, Peter Otten wrote: >> >>> How do I make a regular expression that returns true if the end >> >>> of the line is an asterisk >> >> >> >> Why use a regular expression? >> >> >> >> if line[-1] == '*': >> >> yep(line) >> >> else: >> >> nope(line) >> >> Incidentally the code example has two "problems", too. >> >> - What about the empty string? > > Good catch: .endswith() works better. > >> - What about lines with a trailing "\n", i. e. as they are usually >> delivered when iterating over a file? > > Then your string *doesn't* end with a "*", but rather with a > newline. ;-) > > Though according to the OP's specs, the following function would work > too: > > def ends_in_asterisk(s): > return True > > It *does* return True if the line ends in an asterisk (no requirement > to make the function return False under any other conditions). If a "line" is defined as a string that ends with a newline def ends_in_asterisk(line): return False would also satisfy the requirement. Lies, damned lies, and specs ;) -- https://mail.python.org/mailman/listinfo/python-list
Re: Regular expressions
On 2015-11-02 22:17, Seymore4Head wrote: > On Mon, 2 Nov 2015 20:42:37 -0600, Tim Chase > wrote: > > >On 2015-11-02 20:09, Seymore4Head wrote: > >> How do I make a regular expression that returns true if the end > >> of the line is an asterisk > > > >Why use a regular expression? > > > Because that is the part of Python I am trying to learn at the > moment. Thanks Ah, well that's an entirely different problem-space, so then you would want to use MRAB's answer r = re.compile(r"\*$") -tkc -- https://mail.python.org/mailman/listinfo/python-list
Re: Regular expressions
On 2015-11-03, Tim Chase wrote:
> On 2015-11-02 20:09, Seymore4Head wrote:
>> How do I make a regular expression that returns true if the end of
>> the line is an asterisk
>
> Why use a regular expression?
>
> if line[-1] == '*':
Why use a negative index and then a compare?
if line.endswith('*'):
If you want to know if a string ends with something, just ask it!
;)
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Grant Edwards grant.b.edwardsYow! RELATIVES!!
at
gmail.com
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Re: Regular expressions
Peter Otten writes:
> If a "line" is defined as a string that ends with a newline
>
> def ends_in_asterisk(line):
> return False
>
> would also satisfy the requirement. Lies, damned lies, and specs ;)
Even if a "line" is defined as a string that comes from reading
something like a file with default options, a line may end in
an asterisk.
>>> [ line.endswith('*') for line in StringIO('rivi*\nrivi*\nrivi*') ]
[False, False, True]
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Re: Regular expressions
On Mon, Nov 2, 2015 at 10:17 PM, Seymore4Head wrote: > On Mon, 2 Nov 2015 20:42:37 -0600, Tim Chase > wrote: > > >On 2015-11-02 20:09, Seymore4Head wrote: > >> How do I make a regular expression that returns true if the end of > >> the line is an asterisk > > > >Why use a regular expression? > > > > if line[-1] == '*': > >yep(line) > > else: > >nope(line) > > > >-tkc > > > > > Because that is the part of Python I am trying to learn at the moment. > Are we to infer that you were aware of doing the if line[-1] == '*': ... , but just wanted to learn how to do the same thing with regex? Or that you heard about regexes and thought that would be the way to solve your puzzle? > Thanks > -- > https://mail.python.org/mailman/listinfo/python-list > -- Joel Goldstick http://joelgoldstick.com/stats/birthdays -- https://mail.python.org/mailman/listinfo/python-list
Re: Regular expressions
On Tue, 3 Nov 2015 10:34:12 -0500, Joel Goldstick wrote: >On Mon, Nov 2, 2015 at 10:17 PM, Seymore4Head >wrote: > >> On Mon, 2 Nov 2015 20:42:37 -0600, Tim Chase >> wrote: >> >> >On 2015-11-02 20:09, Seymore4Head wrote: >> >> How do I make a regular expression that returns true if the end of >> >> the line is an asterisk >> > >> >Why use a regular expression? >> > >> > if line[-1] == '*': >> >yep(line) >> > else: >> >nope(line) >> > >> >-tkc >> > >> > >> Because that is the part of Python I am trying to learn at the moment. >> > >Are we to infer that you were aware of doing the if line[-1] == '*': ... >, but just wanted to learn how to do the same thing with regex? Or that you >heard about regexes and thought that would be the way to solve your puzzle? > >> Thanks >> -- >> https://mail.python.org/mailman/listinfo/python-list >> Yes I knew that -1 represents the end character. It is not a question of trying to accomplish anything. I was just practicing with regex and wasn't sure how to express a * since it was one of the instructions. -- https://mail.python.org/mailman/listinfo/python-list
Re: Regular expressions
On Wed, Nov 4, 2015 at 3:10 AM, Seymore4Head wrote: > Yes I knew that -1 represents the end character. It is not a question > of trying to accomplish anything. I was just practicing with regex > and wasn't sure how to express a * since it was one of the > instructions. In that case, it's nothing to do with ending a string. What you really want to know is: How do you match a '*' using a regular expression? Which is what MRAB answered, courtesy of a working crystal ball: You use '\*'. Everything about the end of the string is irrelevant. (So, too, are all the comments about using [-1] or string methods. But we weren't to know that.) ChrisA -- https://mail.python.org/mailman/listinfo/python-list
Re: Regular expressions
Am 03.11.2015 um 05:23 schrieb ru...@yahoo.com: Of course there are people who misuse regexes. /^1?$|^(11+?)\1+$/ There are? 0:-) -- Robin Koch -- https://mail.python.org/mailman/listinfo/python-list
Re: Regular expressions
On 11/03/2015 12:15 AM, Steven D'Aprano wrote: > On Tue, 3 Nov 2015 03:23 pm, rurpy wrote: > >> Regular expressions should be learned by every programmer or by anyone >> who wants to use computers as a tool. They are a fundamental part of >> computer science and are used in all sorts of matching and searching >> from compilers down to your work-a-day text editor. > > You are absolutely right. > > If only regular expressions weren't such an overly-terse, cryptic > mini-language, with all but no debugging capabilities, they would be great. > > If only there wasn't an extensive culture of regular expression abuse within > programming communities, they would be fine. > > All technologies are open to abuse. But we don't say: > > Some people, when confronted with a problem, think "I know, I'll use > arithmetic." Now they have two problems. > > because abuse of arithmetic is rare. It's hard to misuse it, and while > arithmetic can be complicated, it's rare for programmers to abuse it. But > the same cannot be said for regexes -- they are regularly misused, abused, > and down-right hard to use right even when you have a good reason for using > them: > > http://www.thedailywtf.com/articles/Irregular_Expression > > http://blog.codinghorror.com/regex-use-vs-regex-abuse/ > > http://psung.blogspot.com.au/2008/01/wonderful-abuse-of-regular-expressions.html Thanks for pointing out three cases of misuse of regexes out of the approximately 37500 [*] uses of regexes in the wild. I hope you're not dumb enough to think that constitutes significant evidence. Even worse, of the three only one was a real example. One of the others was machine-generated code, the other was a "look what you can do with regexes" example, not serious code. Here is an example of "abusing" python https://benkurtovic.com/2014/06/01/obfuscating-hello-world.html I wouldn't use this as evidence that Python is to be avoided. > If there is one person who has done more to create a regex culture, it is > Larry Wall, inventor of Perl. Even Larry Wall says that regexes are > overused and their syntax is harmful, and he has recreated them for Perl 6: > > http://www.perl.com/pub/2002/06/04/apo5.html You really should have read beyond the first paragraph. He proposes fixing regexes by adding even more special character combinations and making regexes even *more* powerful. (He turned them into full-blown parsers.) Nowhere does he advocate not using, or avoiding if possible, regexes as is the mantra in this list. Here is Larry's "recreation" that you are touting: http://design.perl6.org/S05.html Please explain to us how you think this "fix" addresses the complaints you and other Python anti-regexers have about regexes. I hope you also noted Larry's tongue-in-cheek writing style. Right after pointing out that some claim Perl is hard to read due largely to regex syntax, he writes: "Funny that other languages have been borrowing Perl's regular expressions as fast as they can..." So I don't think you can claim Larry Wall as a supporter of this list's anti-regex attitude beyond some superficial verbiage taken out of context. > Oh, and the icing on the cake, regexes can be a security vulnerability too: > https://www.owasp.org/index.php/Regular_expression_Denial_of_Service_-_ReDoS And here is a list of CVEs involving Python. There are (at time of writing) 190 of them. http://cve.mitre.org/cgi-bin/cvekey.cgi?keyword=python So if a security vulnerability is reason not to use regexes, we should all be *running* from Python. I sure you'll point out that most have been fixed. But you failed to point out that same is true of regex engines. From your source: "Notice, that not all algorithms are naïve, and actually Regex algorithms can be written in an efficient way." And in fact, again, had you looked beyond a headline that suited your purpose, you could have tried the "Evil Regexes" noted in that source and discovered none of them are a DoS in Python. Even were that not true, normal practice applies: if the input is untrusted then sanitize it, or mitigate the threat by imposing a timeout, etc. Not exactly a problem or solution unique to regexes. And common sense should tell you that since there are a lot of "try a regex" web sites, this is not a problem without a solution. And *certainly* not a reason not to use them in the *far* more common case when they *are* trusted because you are in control of them, Finally, preemptively, I'll repeat I acknowledge regexs are not the the optimum solution in every case where they could be used. But they are very useful when one passes the border of the trivial; and they are nowhere near as bad as routinely portrayed here. [*] Yes, I made that number up. -- https://mail.python.org/mailman/listinfo/python-list
Re: Regular expressions
On Monday, November 2, 2015 at 9:38:24 PM UTC-7, Michael Torrie wrote: > On 11/02/2015 09:23 PM, rurpy--- via Python-list wrote: > >> My completely unsolicited advice is that regular expressions shouldn't be > >> very high on the list of things to learn. They are very useful, and very > >> tricky and prone many problems that can and should be learned to be > >> resolved with much simpler methods. If you really want to learn regular > >> expressions, that's great but the problem you posed is not one for which > >> they are the best solution. Remember simpler is better than complex. > > > > Regular expressions should be learned by every programmer or by anyone > > who wants to use computers as a tool. They are a fundamental part of > > computer science and are used in all sorts of matching and searching > > from compilers down to your work-a-day text editor. > > > > Not knowing how to use them is like an auto mechanic not knowing how to > > use a socket wrench. > > Not quite. Core language concepts like ifs, loops, functions, > variables, slicing, etc are the socket wrenches of the programmer's > toolbox. Regexs are like an electric impact socket wrench. You can do > the same work without it, but in many cases it's slower. But you have to > learn the other hand tools first in order to really use the electric > driver properly (understanding torques, direction of threads, etc), lest > you wonder why you're breaking off so many bolts with the torque of the > impact drive. I consider regexs more fundemental. One need not even be a programmer to use them: consider grep, sed, a zillion editors, database query languages, etc. When there is a mini-language explicitly developed for describing string patterns, why, except is very simple cases, would one not take advantage of it? Beyond trivial operations a regex, although terse (overly perhaps), is still likely to be more understandable more maintainable than bunch of ad-hoc code. And the relative ease of expressing complex patterns means one is more likely to create more specific patterns, resulting in detecting unexpected input earlier than with ad-hoc code. -- https://mail.python.org/mailman/listinfo/python-list
Re: Regular expressions
On 11/03/2015 05:33 PM, rurpy--- via Python-list wrote: > I consider regexs more fundemental. One need not even be a programmer > to use them: consider grep, sed, a zillion editors, database query > languages, etc. Grep can use regular expressions (and I do so with it regularly), but it's default mode is certainly not regular expressions, and it is still very powerful. I've never used regular expressions in a database query language; until this moment I didn't know any supported such things in their queries. Good to know. How you would index for regular expressions in queries I don't know. > When there is a mini-language explicitly developed for describing > string patterns, why, except is very simple cases, would one not > take advantage of it? Mainly because the programming language itself often can do it just as cleanly and just as fast (slicing, string methods, etc). I certainly programmed for many years without needing regular expressions in my small projects. In fact, REs are a bit of a pain to use in, say, C or C++, requiring a library. With Python they are much more readily accessible so I use them much more. But honestly it wasn't until college when I learned about finite state automata that I really grasped what regular expressions were and how to use them. > Beyond trivial operations a regex, although > terse (overly perhaps), is still likely to be more understandable > more maintainable than bunch of ad-hoc code. And the relative ease > of expressing complex patterns means one is more likely to create > more specific patterns, resulting in detecting unexpected input > earlier than with ad-hoc code. Maybe, maybe not. Using Python string class methods is probably more clear when such methods are sufficient. -- https://mail.python.org/mailman/listinfo/python-list
