There is no way to create a SpecifierSet directly from one or more Specifiers

[pfmoore]

The SpecifierSet constructor takes a string as input. But if you have a list of Specifier objects, there's no way to make a SpecifierSet from them without converting them back to strings and re-parsing.

Could a classmethod be added to build a specifier set from an iterable of Specifiers? It could be as simple as

@classmethod
def from_specifiers(cls, specs: Iterable[Specifier], prerelease: Optional[bool] = None):
    new_value = cls()
    new_value._specs = specs
    new_value._prereleases = prereleases
    return new_value

I'd be happy to create a PR for this if the idea is acceptable.

[pfmoore]

On reflection, this probably doesn't need a new classmethod - simply allowing construction from an iterator of Specifier instances should be fine.

I've created #777 implementing this.