I wish to replace several characters in my string to only one.
Example, "-", "." and "/" to nothing ""
I did like that:
my_string = my_string.repla ce("-", "").replace("." , "").replace ("/",
"").replace(")" , "").replace("(" , "")
But I think it's a ugly way.
What's the better way to do it?
Aug 13 '08
15  1585 
On Aug 14, 8:50 am, Wojtek Walczak
<gmin...@nie.ma .takiego.adresu .w.sieci.plwrot e:
Dnia Thu, 14 Aug 2008 00:31:00 +0200, Fredrik Lundh napisa³(a):
> if ch in my_string:
my_string = my_string.repla ce(ch, "")
>on representative data.
I don't have to, I can anticipate the results.
Chances are that you're wrong.
At the moment my average is about 0.75 of mistake per
post on comp.lang.pytho n (please, bare with me ;-)).
I strongly believe that the statement I made above won't
make this number rise.
Meta-mistake: Playing poker with the effbot. If he says diffidently
that he'll raise you a dime, it means he's holding five aces :-)
Clue: The effbot was the original author of the modern (Python 1.6?)
version of the re module.
HTH,
John
On Wed, 13 Aug 2008 22:50:29 +0000, Wojtek Walczak wrote:
Dnia Thu, 14 Aug 2008 00:31:00 +0200, Fredrik Lundh napisa³(a):
>>> if ch in my_string:
my_string = my_string.repla ce(ch, "")
on representative data.
I don't have to, I can anticipate the results.
Chances are that you're wrong.
At the moment my average is about 0.75 of mistake per post on
comp.lang.pytho n (please, bare with me ;-)). I strongly believe that the
statement I made above won't make this number rise.
:)
Okay, is this going to be one of those things where, no matter what the
benchmarks show, you say "I was right, I *did* anticipate the results. I
just anticipated them correctly/incorrectly."?
If so, you get an A+ in pedantry and F- in usefulness *wink*
In full knowledge that Python is relatively hard to guess what is fast
compared to what is slow, I'll make my guess of fastest to slowest:
1. repeated replace
2. repeated use of the form
"if ch in my_string: my_string = my_string.repla ce(ch, "")
3. re.sub with literal replacement
4. re.sub with callback (lambda m: "")
Results to follow.
--
Steven
Steven D'Aprano wrote:
While I'm gratified that my prediction was so close to the results I
found, I welcome any suggestions to better/faster/more efficient code.
more things to try:
code tweaks:
- Factor out the creation of the regular expression from the tests:
"escape" and "compile" are relatively expensive, and neither throw-away
code (using the RE function forms) nor production code will end up doing
them both for each string.
- Same w. the translation table for "translate"
- Use Unicode strings instead of byte strings (we're moving towards 3.0,
after all).
test data variations:
- Try dropping the number of actual replacements and see what happens --
if you're escaping user-provided data (e.g. HTML), for example, it's not
that unlikely that you end up doing only a few replacements for each
string you're processing, or no replacements at all.
- Also try shorter and longer strings ("human-sized" data is often
provided in shorter chunks than 216 characters per string; the typical
size and distribution depends on your actual application, of course).
Unicode will affect translate more than the others; the last two will
most likely affect in-replace instead (that approach gets faster the
shorter the strings are, and the fewer calls to replace that you
actually end up doing).
Finally, if you want the sub-lambda form to look better, try inserting a
character before or after each special character using a template string
or a lambda (e.g. a backslash).
</F>
John Machin wrote:
Clue: The effbot was the original author of the modern (Python 1.6?)
version of the re module.
And the author of the "in" and "replace" implementations in Python 2.5.
</F>
On 2008-08-13 23:54, John Krukoff wrote:
On Wed, 2008-08-13 at 09:39 -0700, gjhames wrote:
>I wish to replace several characters in my string to only one.
Example, "-", "." and "/" to nothing ""
I did like that:
my_string = my_string.repla ce("-", "").replace("." , "").replace ("/",
"").replace(") ", "").replace("(" , "")
But I think it's a ugly way.
What's the better way to do it?
--
http://mail.python.org/mailman/listinfo/python-list
The maketrans interface is a bit clunky, but this is what
string.translat e is best at:
>>import string
>>>'-./other'.translat e( string.maketran s( '', '' ), '-./' )
'other'
It'd be interesting to see where it falls in the benchmarks, though.
It's worth noting that the interface for translate is quite different
for unicode strings.
Right. Unicode .translate() uses a dictionary for defining the
mapping.
Another approach is to use the re module:
>>import re
re.sub('[-./()]', '', '-./other')
'other'
--
Marc-Andre Lemburg
eGenix.com
Professional Python Services directly from the Source (#1, Aug 14 2008)
>>Python/Zope Consulting and Support ... http://www.egenix.com/
mxODBC.Zope.D atabase.Adapter ... http://zope.egenix.com/
mxODBC, mxDateTime, mxTextTools ... http://python.egenix.com/
_______________ _______________ _______________ _______________ ____________
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eGenix.com Software, Skills and Services GmbH Pastor-Loeh-Str.48
D-40764 Langenfeld, Germany. CEO Dipl.-Math. Marc-Andre Lemburg
Registered at Amtsgericht Duesseldorf: HRB 46611
On 14 Aug 2008 01:54:55 GMT, Steven D'Aprano wrote:
>>>I don't have to, I can anticipate the results.
Chances are that you're wrong.
At the moment my average is about 0.75 of mistake per post on
comp.lang.pyth on (please, bare with me ;-)). I strongly believe that the
statement I made above won't make this number rise.
Okay, is this going to be one of those things where, no matter what the
benchmarks show, you say "I was right, I *did* anticipate the results. I
just anticipated them correctly/incorrectly."?
Don't count on it. I never really cared about being right or wrong
and I am not one of those guys who are trying to prove something
that actually makes no difference at all. Nice tests, though :)
--
Regards,
Wojtek Walczak, http://www.stud.umk.pl/~wojtekwa/ This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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