[Distutils] [Python-Dev] [Python-checkins] peps: PEP 426: replace implied 'version starts with' with new ~= operator

[Daniel Holth]

On Tue, Feb 26, 2013 at 8:17 AM, Nick Coghlan <ncoghlan at gmail.com> wrote:

> On Tue, Feb 26, 2013 at 10:08 PM, Michael Foord <fuzzyman at gmail.com>
> wrote:
> > The current tools are strict with regards to equality - and in dependency
> > pinning I would see it as *surprising* that specifying "==1.3" installs
> some
> > version that isn't precisely 1.3. Having "==" mean approximately-equal,
> > instead of the-same-as, seems like a mistake to me.
>
> The most palatable alternative I've seen so far is for a trailing ".*"
> to trigger prefix matching for == and != (it would be disallowed for
> anything else). It's *slightly* odd, because the "." is implied rather
> than explicit for alphas, betas and release candidates (a choice
> driven by the weight of existing practice on PyPI, as well as
> CPython's own conventions), but it's probably still a better idea than
> trying to change the meaning of "==".
>
> I *don't* like the idea of (== 1.3) and (== 1.3.0) being equivalent
> when (1.3) and (1.3.0) are substantially different, though. Instead,
> I'll reinstate a variant of the commentary from PEP 386 that pointed
> out the value of always publishing releases with a consistent number
> of components by including the trailing ".0".


I am still not convinced about the prefix behavior but realize that if we
are using sensible consistently three-digit releases then there is no
problem.

There is an algorithm for splitting "version parts" at either . or the
transition from a number to a non-number or vice versa. In pkg_resources
1.1a1 and 1.1.a1 are the same.
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