On 7/2/2019 12:16 AM, Glenn Linderman wrote:
On 7/1/2019 8:28 PM, Terry Reedy wrote:
I did not read much of the thread, but the proposal is to wrap a
near-trivial expression (2 operations) or replace a current method
call with a method call than is more or less the same len as what it
replaces.
>>> 'prefix_more_suffix'[len('prefix'):] # if know s begins with p
'_more_suffix'
>>> 'prefix_more_suffix'.replace('prefix', '')
'_more_suffix'
>>> 'prefix_more_suffix'.strip_pre('prefix') # proposed
Your example isn't equivalent: .replace would replace multiple instances
of prefix, not necessarily at the beginning. The .strip_pre (however
spelled) would strip one instance, only if it is at the beginning.
I left out the slightly longer regex which does exactly that.
>>> re.sub('^prefix', '', 'prefix_more_suffix')
'_more_suffix'
>>> re.sub('^prefix', '', 'Xprefix_more_suffix')
'Xprefix_more_suffix'
or with minor variation, deletes only suffixes.
>>> re.sub('suffix$', '', 'prefix_more_suffix')
'prefix_more_'
Are these special cases, which can be easily generalized to match more
than one string, and to replace rather than delete, special enough to
merit a new method each. This remains to be demonstrated.
The more I thought about this, the more I think a more functional goal
is a variation of replace that works only on one end or the other,
rather than a variation of strip. I outlined that in a different branch
in this thread.
To me, a new parameter to str.replace would have a lower bar to acceptance.
The other documentation issue I noticed is that the 2nd and 3rd
parameters to startswith and endswith are not fully documented.
Typically startswith and endswitch are in the logic prior to the
strip/replace operation, and typically only use the first parameter, but
looking at their documentation as part of this discussion, I found it
lacking.
File an issue? Preferably with a suggested change.
--
Terry Jan Reedy
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