Curious to see alternate approach on a search/replace via regex

Nick Mellor thebalancepro at gmail.com
Fri Feb 8 09:53:12 CET 2013


Hi RH,

It's essential to know about regex, of course, but often there's a better, easier-to-read way to do things in Python.

One of Python's aims is clarity and ease of reading.

Regex is complex, potentially inefficient and hard to read (as well as being the only reasonable way to do things sometimes.)

Best,

Nick

On Friday, 8 February 2013 16:47:03 UTC+11, rh  wrote:
> On Thu, 7 Feb 2013 04:53:22 -0800 (PST)
> 
> Nick Mellor <t...o at gmail.com> wrote:
> 
> 
> 
> > Hi RH,
> 
> > 
> 
> > translate methods might be faster (and a little easier to read) for
> 
> > your use case. Just precompute and re-use the translation table
> 
> > punct_flatten.
> 
> > 
> 
> > Note that the translate method has changed somewhat for Python 3 due
> 
> > to the separation of text from bytes. The is a Python 3 version.
> 
> > 
> 
> > from urllib.parse import urlparse
> 
> > 
> 
> > flattened_chars = "./&=?"
> 
> > punct_flatten = str.maketrans(flattened_chars, '_' * len
> 
> > (flattened_chars)) parts = urlparse
> 
> > ('http://alongnameofasite1234567.com/q?sports=run&a=1&b=1')
> 
> > unflattened = parts.netloc + parts.path + parts.query flattened =
> 
> > unflattened.translate(punct_flatten) print (flattened)
> 
> 
> 
> I like the idea of using a library but since I'm learning python I wanted
> 
> to try out the regex stuff. I haven't looked but I'd think that urllib might
> 
> (should?) have a builtin so that one wouldn't have to specify the 
> 
> flattened_chars list. I'm sure there's a name for those chars but I don't know
> 
> it. Maybe just punctuation??
> 
> 
> 
> Also my version converts the ? into _ but urllib sees that as the query
> 
> separator and removes it. Just point this out for completeness sake.
> 
> 
> 
> This would mimic what I did:
> 
> unflattened = parts.netloc + parts.path + '_' + parts.query
> 
> 
> 
> > 
> 
> > Cheers,
> 
> > 
> 
> > Nick
> 
> > 
> 
> > On Thursday, 7 February 2013 08:41:05 UTC+11, rh  wrote:
> 
> > > I am curious to know if others would have done this differently.
> 
> > > And if so
> 
> > > 
> 
> > > how so?
> 
> > > 
> 
> > > 
> 
> > > 
> 
> > > This converts a url to a more easily managed filename, stripping the
> 
> > > 
> 
> > > http protocol off. 
> 
> > > 
> 
> > > 
> 
> > > 
> 
> > > This:
> 
> > > 
> 
> > >  
> 
> > > 
> 
> > > http://alongnameofasite1234567.com/q?sports=run&a=1&b=1
> 
> > > 
> 
> > > 
> 
> > > 
> 
> > > becomes this:
> 
> > > 
> 
> > > 
> 
> > > 
> 
> > > alongnameofasite1234567_com_q_sports_run_a_1_b_1
> 
> > > 
> 
> > > 
> 
> > > 
> 
> > > 
> 
> > > 
> 
> > > def u2f(u):
> 
> > > 
> 
> > >     nx = re.compile(r'https?://(.+)$')
> 
> > > 
> 
> > >     u = nx.search(u).group(1)
> 
> > > 
> 
> > >     ux = re.compile(r'([-:./?&=]+)')
> 
> > > 
> 
> > >     return ux.sub('_', u)
> 
> > > 
> 
> > > 
> 
> > > 
> 
> > > One alternate is to not do the compile step. There must also be a
> 
> > > way to
> 
> > > 
> 
> > > do it all at once. i.e. remove the protocol and replace the chars.
> 
> 
> 
> 
> 
> --



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