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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def percent_at_home(positions, user):
 """ The percentage of interactions the user had while he was at home. .. note:: The position of the home is computed using :meth:`User.recompute_home <bandicoot.core.User.recompute_home>`. If no home can be found, the percentage of interactions at home will be ``None``. """


    if not user.has_home:
        return None

    total_home = sum(1 for p in positions if p == user.home)
    return float(total_home) / len(positions) if len(positions) != 0 else 0