Version numbering for anarchists and software realists.
Implements the standard interface for version number classes as
described above.  A version number consists of a series of numbers,
separated by either periods or strings of letters.  When comparing
version numbers, the numeric components will be compared
numerically, and the alphabetic components lexically.  The following
are all valid version numbers, in no particular order:

    1.5.1
    1.5.2b2
    161
    3.10a
    8.02
    3.4j
    1996.07.12
    3.2.pl0
    3.1.1.6
    2g6
    11g
    0.960923
    2.2beta29
    1.13++
    5.5.kw
    2.0b1pl0

In fact, there is no such thing as an invalid version number under
this scheme; the rules for comparison are simple and predictable,
but may not always give the results you want (for some definition
of "want").

>>> from distutils.version import LooseVersion as V
>>> v1 = V('FunkyVersion')
>>> v2 = V('GroovieVersion')
>>> v1 > v2
False

Version numbering for meticulous retentive and software idealists.
Implements the standard interface for version number classes as
described above.  A version number consists of two or three
dot-separated numeric components, with an optional "pre-release" tag
on the end.  The pre-release tag consists of the letter 'a' or 'b'
followed by a number.  If the numeric components of two version
numbers are equal, then one with a pre-release tag will always
be deemed earlier (lesser) than one without.

The following are valid version numbers (shown in the order that
would be obtained by sorting according to the supplied cmp function):

    0.4       0.4.0  (these two are equivalent)
    0.4.1
    0.5a1
    0.5b3
    0.5
    0.9.6
    1.0
    1.0.4a3
    1.0.4b1
    1.0.4

The following are examples of invalid version numbers:

    1
    2.7.2.2
    1.3.a4
    1.3pl1
    1.3c4

>>> from distutils.version import StrictVersion as V
>>> v2 = V('GroovieVersion')
Traceback (most recent call last):
...
ValueError: invalid version number 'GroovieVersion'
>>> v2 = V('1.1')
>>> v3 = V('1.3')
>>> v2 < v3
True

Convert a version string to a chronologically-sortable key

This is a rough cross between Distutils' StrictVersion and LooseVersion;
if you give it versions that would work with StrictVersion, then it behaves
the same; otherwise it acts like a slightly-smarter LooseVersion. It is
*possible* to create pathological version coding schemes that will fool
this parser, but they should be very rare in practice.

The returned value will be a tuple of strings.  Numeric portions of the
version are padded to 8 digits so they will compare numerically, but
without relying on how numbers compare relative to strings.  Dots are
dropped, but dashes are retained.  Trailing zeros between alpha segments
or dashes are suppressed, so that e.g. "2.4.0" is considered the same as
"2.4". Alphanumeric parts are lower-cased.

The algorithm assumes that strings like "-" and any alpha string that
alphabetically follows "final"  represents a "patch level".  So, "2.4-1"
is assumed to be a branch or patch of "2.4", and therefore "2.4.1" is
considered newer than "2.4-1", which in turn is newer than "2.4".

Strings like "a", "b", "c", "alpha", "beta", "candidate" and so on (that
come before "final" alphabetically) are assumed to be pre-release versions,
so that the version "2.4" is considered newer than "2.4a1".

Finally, to handle miscellaneous cases, the strings "pre", "preview", and
"rc" are treated as if they were "c", i.e. as though they were release
candidates, and therefore are not as new as a version string that does not
contain them, and "dev" is replaced with an '@' so that it sorts lower
than any other pre-release tag.

>>> from pkg_resources import parse_version as V
>>> V('1.2')
('00000001', '00000002', '*final')
>>> V('1.2b2')
('00000001', '00000002', '*b', '00000002', '*final')
>>> V('FunkyVersion')
('*funkyversion', '*final')

>>> from verlib import NormalizedVersion
>>> version = NormalizedVersion('1.0')

>>> str(version)
'1.0'

>>> NormalizedVersion('1.0') > NormalizedVersion('0.9')
True
>>> NormalizedVersion('1.0') < NormalizedVersion('1.1')
True

>>> version = NormalizedVersion.from_parts((1, 0))
>>> str(version)
'1.0'

>>> version = NormalizedVersion.from_parts((1, 0), ('c', 4))
>>> str(version)
'1.0c4'

>>> version = NormalizedVersion.from_parts((1, 0), ('c', 4), ('dev', 34))
>>> str(version)
'1.0c4.dev34'

>>> from verlib import suggest_normalized_version, NormalizedVersion
>>> import warnings
>>> def validate_version(version):
...     rversion = suggest_normalized_version(version)
...     if rversion is None:
...         raise ValueError('Cannot work with "%s"' % version)
...     if rversion != version:
...         warnings.warn('"%s" is not a normalized version.\n'
...                       'It has been transformed into "%s" '
...                       'for interoperability.' % (version, rversion))
...     return NormalizedVersion(rversion)
...

>>> validate_version('2.4-rc1')
__main__:8: UserWarning: "2.4-rc1" is not a normalized version.
It has been transformed into "2.4c1" for interoperability.
NormalizedVersion('2.4c1')

>>> validate_version('2.4c1')
NormalizedVersion('2.4c1')

>>> validate_version('foo')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 4, in validate_version
ValueError: Cannot work with "foo"