def versions_from_trove(trove):
    """Finds out python version from list of trove classifiers.
    Args:
        trove: list of trove classifiers
    Returns:
        python version string
    """
    versions = set()
    for classifier in trove:
        if 'Programming Language :: Python ::' in classifier:
            ver = classifier.split('::')[-1]
            major = ver.split('.')[0].strip()
            if major:
                versions.add(major)
    return sorted(
        set([v for v in versions if v.replace('.', '', 1).isdigit()]))