confused about error using lambda function

You create a function, but don't actually call it. You can change this in two ways: call the lambda or don't use a lambda function. In this case the second would be better, but if you just want to learn about lambda functions you might use the first.

print("the sum is {}".format((lambda a,b:a+b)(a, b)))
print("the multiple is {}".format((lambda a,b:a*b)(a, b)))

The change I made was to replace the lambda with (lambda a,b:a+b)(a, b)

or just remove the lambda

print("the sum is {}".format(a+b))
print("the multiple is {}".format(a*b))

This would be the better option in this case.

lambda is the way of writing anonymous function but they are still functions you need to call them.

a=int(input("a number: "))
b=int(input("another number: "))
print("the sum is {}".format((lambda a,b:a+b)(a,b)))
print("the multiple is {}".format((lambda a,b:a*b)(a,b)))

Output:

a number: 1
another number: 2
the sum is 3
the multiple is 2

There is no error in your output. Since lambda is a function, when you print it you see <function <lambda> at 0x000001B6BF941B88>.

If you want to invoke it, try:

a=int(input("a number: "))
b=int(input("another number: "))
sum_func = lambda a,b:a+b
product_func = lambda a,b:a*b
print("the sum is {}".format(sum_func(a,b)))
print("the multiple is {}".format(product_func(a,b)))

Try storing it in a variable.

    #to add and multiply numbers using lambda in python
    a=int(input("a number: "))
    b=int(input("another number: "))
    add = lambda a,b:a+b
    mult = lambda a,b:a*b
    print("the sum is {}".format(add(a,b)))
    print("the multiple is {}".format(mult(a,b)))