On 2019-01-28 18:22, David Mertz wrote:
On Mon, Jan 28, 2019 at 8:44 PM Jamesie Pic <j...@yourlabs.org
<mailto:j...@yourlabs.org>> wrote:
['cancel', name].join('_')
This is a frequent suggestion. It is also one that makes no sense
whatsoever if you think about Python's semantics. What would you expect
to happen with this line:
['foo', b'foo', 37, re.compile('foo')].join('_')
List are not restricted to containing only strings (or things that are
string-like enough that they might play well with joining). Growing a
method that pertains only to that specialized sort of list breaks the
mental model of Python. Moreover, there is no way to TELL if a
particular list is a "list of strings" other than checking each item
inside it (unlike in many languages).
That problem already exists with str.join though. It's just currently
spelled this way:
','.join(['foo', b'foo', 37, re.compile('foo')])
. . . and the result is an error. I don't see how it's semantically
any less sensible to call list.join on a list of non-string things than
it is to pass a list of non-string things to str.join.
Personally what I find is perverse is that .join is a method of strings
but does NOT call str() on the items to be joined. The cases where I
would have been surprised or bitten by something accidentally being
converted to a string are massively outweighed by the cases where I want
everything to be converted into a string, because, dangit, I'm joining
them into a bigger string.
I agree that a list method would be nice, but we then have to think
about should we add similar methods to all iterable types, since
str.join can take any iterable (not just a list).
--
Brendan Barnwell
"Do not follow where the path may lead. Go, instead, where there is no
path, and leave a trail."
--author unknown
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