def number_valid(value):
    """Test for valid number

    >>> number_valid(0)
    True
    >>> number_valid(-1)
    True
    >>> number_valid(1.12039123)
    True
    >>> number_valid('1.12039123')
    True
    >>> number_valid('x1.12039123')
    False
    >>> number_valid('t')
    False
    >>> number_valid('')
    True
    >>> number_valid(False) # not sure if this is what's we want
    True
    """
    if value == '':
        return True
    try:
        float(value)
        return True
    except ValueError:
        return False