Python Reverse the binary equivalent of input and output the integer equivalent of the reverse binary
x  = 0


There is no point in doing this. You just replace it anyways

while True:

    try:
        x = int(raw_input('input a decimal number \t'))


        if x in xrange(1,1000000001):


Probably better to use if 1 &lt;= x &lt;= 100000000001: although I'm really not sure why you are doing this check. Also, you should probably explain to the user that you've reject the number.

            y = bin(x)

            rev = y[2:]


I'd use reversed = bin(x)[:1::-1] rather then splitting it out across the tree lines.

        print("the reverse binary soln for the above is %d") %(int('0b'+rev[::-1],2))    


I'd convert the number before the print to seperate output from the actual math.

            break

    except ValueError:
        print("Please input an integer, that's not an integer")
        continue


This continue does nothing.