why does '10' is less than '7' or less while we are sorting? : >>> '10'>'3'
    False
    >>>
    >>> a=['10','9','8','7']
    >>> a.sort()
    >>> a
    ['10', '7', '8', '9']
    >>>
    why '10' is less than '3' ? I tried with several more 
    values but the same thing is happening with it.

    >>> '10'>'3'
    False
    >>>
    >>> a=['10','9','8','7']
    >>> a.sort()
    >>> a
    ['10', '7', '8', '9']
    >>>

I expect the output of '10'>'3' to be True