On Thu, Mar 05, 2020 at 12:45:28PM -0800, Andrew Barnert via Python-ideas wrote:
> Well, I like the idea if someone can come up with a good naming
> scheme—something that at least reminds me which function is the “set
> of chars” stripper and which the “substring” stripper,
You've been a Python programmer for how many years now? Do you currently
have trouble remembering what lstrip and rstrip do? If not, I doubt you
will suddenly forget their meaning because we add a pair of new methods
with quite different names.
Unless, of course, we go down the path of a foolish consistency and
choose names which are too similar:
lcut
lremove
ldelete
in which case you are right, people would certainly confuse the two. So
let's not do that :-)
This proposal isn't for a generic "substring" stripper. We already have
that, it is called str.replace. This proposal is specifically for
removing *prefixes and suffixes* not arbitrary substrings.
Referencing the words "prefix" and "suffix" is not "gratuitously" adding
"yet another way to say l/left/start" but a critical part of the
methods' semantics. If we were to describe what the proposed methods do,
we surely would say something like these:
cut the prefix
delete the prefix
remove the prefix
strip the prefix
trim the prefix
because that is what the method does: it cuts/deletes etc the *prefix*,
not some arbitrary substring or set of characters. But we wouldn't say:
cut the substring on the left
because "on the left" is not sufficient. How far on the left? Can the
substring be anywhere in the left half of the string?
"The red peppers are very red and fresh".cut_left_substring("red")
=> "The peppers are very red and fresh"
I hope that we can agree that some names are simply too long and
cumbersome:
str.cut_substring_all_the_way_on_left(prefix)
We already have `[l|r]strip` methods. If we want to associate the new
methods with those, I suggest
strip_prefix
strip_suffix
which will show up right next to `strip` in the docs and state
explicitly what they do. (Personally, I prefer to add a little more
conceptual distance by calling the method "cut_" but I'm willing to
accept "strip" if others like it.)
I trust that is clear enough. If not, what else could "strip prefix"
mean, if not strip the prefix?
Contrast:
lstrip_string
"Yes, I know it operates on a string, it's a string method after all.
But what does it do?"
The following is a tangential note about some Python history, and isn't
really relevant to the proposal as such. So you can stop reading here
without missing anything important.
[Christopher]
> > 1) I don’t think any other string methods take keywords.
[Andrew]
> Sure, but they mostly go back to the days before keyword arguments
> existed at all, much less now when they can be implemented relatively
> easily even in C functions.
Keywords predate string methods.
String methods were only added in Python 2.0:
https://docs.python.org/2.0/lib/string-methods.html
In Python 1.5, strings had no methods:
>>> 'a'.upper()
Traceback (innermost last):
File "<stdin>", line 1, in ?
AttributeError: 'string' object has no attribute 'upper'
and we used the "string" module functions. I don't see any builtins with
keyword arguments in Python 1.5:
https://docs.python.org/release/1.5/lib/node26.html
but pure Python functions certainly had them. Since string functions
were originally written in Python, they could have had keyword
arguments had they been desired.
--
Steven
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