Extracting parts of string between anchor points
cs at zip.com.au
Thu Feb 27 22:40:12 CET 2014
On 27Feb2014 20:07, Jignesh Sutar <jsutar at gmail.com> wrote:
> I've kind of got this working but my code is very ugly. I'm sure it's
> regular expression I need to achieve this more but not very familiar with
> use regex, particularly retaining part of the string that is being
> searched/matched for.
Regexps are quite useful for very variable text. You're just splitting
on ':' and '-:-', which is very easy and does not need a regexp.
Avoid regexps if the code can be written easily and readably without
them; they are cryptic and fragile.
> Notes and code below to demonstrate what I am trying to achieve. Any help,
> much appreciated.
> "Test2A: Test2B",
> "Test3A: Test3B -:- Test3C", ""]
Minor remark. Class names tend to have leading uppercase names,
like Foo. ordinary variables tend to have lower case names, like
foo. A habit to get into - it maes your code more readable for
Code suggestions below the code...
> # Out1 is just itself unless if it is empty
> # Out2 is everything left of ":" (including ":" i.e. part A) and right of
> "-:-" (excluding "-:-" i.e. part C)
> # If text doesn't contain "-:-" then return text itself as it is
> # Out3 is everything right of "-:-" (excluding "-:-" i.e. part C)
> # If text doesn't contain "-:-" but does contains ":" then return part B
> # If it doesn't contain ":" then return itself (unless if it empty then
> for i,s in enumerate(Examples,start=1):
> Out1=s if len(s)>0 else "Empty"
> Out2=s[:s.find(":")+3] + s[s.find("-:-")+5:] if s.find("-:-")>0 else
> s.strip() if len(s) else "Empty"
> Out3=s[s.find("-:-")+4:] if s.find("-:-")>0 else
> s[s.find(":")+1:].strip() if s.find(":")>0 and len(s)!=s.find(":")+1 else s
> if len(s) else "Empty"
> print "Item%(i)s <%(s)s> Out1 = %(Out1)s" % locals()
> print "Item%(i)s <%(s)s> Out2 = %(Out2)s" % locals()
> print "Item%(i)s <%(s)s> Out3 = %(Out3)s" % locals()
I would be parsing the string using "split", progressively.
Example (completely untested):
# initialise all parts because we will only set the parts
# below if they appear in the text
out1, out2, out3 = '', '', ''
words = s.split(':', 1)
if words: # arrays are false if empty, true if non-empty
out1 = words.pop(0)
# there is a second part - split it on "-:-"
words = words.split('-:-', 1)
out2 = words.pop(0)
out3 = words.pop(0)
# personally I would leave out1 etc as empty strings and only _print_ the word "Empty"
# but if you really want to mangle the variables themselves:
if not out1:
out1 = "Empty"
if not out2:
out2 = "Empty"
if not out3:
out3 = "Empty"
Notice that by using split we do not need to do any funny string
Cameron Simpson <cs at zip.com.au>
You can't have everything... where would you put it?
- Charles Robinson, cr0100 at medtronic.com
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