text: Computing weighted sum of first 9 digits
code: _sum = 0 NEW_LINE for i in range ( 9 ) : NEW_LINE INDENT if 0 <= int ( isbn [ i ] ) <= 9 : NEW_LINE INDENT _sum += int ( isbn [ i ] ) * ( 10 - i ) NEW_LINE DEDENT else : NEW_LINE INDENT return False NEW_LINE DEDENT DEDENT