platform.py

class Platform(tuple):
    """
    A sorted tuple of pairs whose first element is a string.  As in a
    dict's items(), no string should appear as the first item in more
    than one unique pair.

    >>> a = Platform({'os':'linux', 'cc':'gcc'})
    >>> a
    Platform({'cc': 'gcc', 'os': 'linux'})
    >>> print a
    gcc-linux
    >>> x = {}
    >>> b = Platform({'os':'linux', 'cc':'gcc'})
    >>> x[a] = 1
    >>> x[b]
    1
    >>> x.get(Platform({'os':'win', 'cc':'gcc'}))
    >>>
    """
    def __new__(cls, rhs):
        if isinstance(rhs, dict):
            rhs = rhs.iteritems()
        return tuple.__new__(cls, sorted(rhs))

    def __str__(self):
        return '-'.join(str(x[1]) for x in self)

    def __repr__(self):
        return self.__class__.__name__ + '({' + ', '.join(
            repr(k) + ': ' + repr(v) for k,v in self) + '})'

if __name__ == "__main__":
    import doctest
    doctest.testmod()