Python Lambda function for negative number

Question

I use a lambda function to convert a decimal negative number to binary two's complement. However the result is not a binary number.

My code:

num1 = int(raw_input("Enter first number"))

if num1  < 0:
def tobin(x, count = 8):
     return "".join(map(lambda y:str((x>>y)&1), range(count-1, -1, -1)))
    num1 = tobin
print num1

Result:

Enter first number -5
<function tobin at 0x1f9c260>

The expected result should be 1011.

Answer 1

num1 = int(raw_input("Enter first bumber:\t"))

def tobin(x, count=4):
    return "".join(map(lambda y: str((x >> y) & 1), range(count - 1, -1, -1)))
if num1  < 0:
    num1 = tobin(num1)
print num1

result:

Enter first bumber: -5
1011