How does the syntax "exp1 << variable << exp2" work in Python?

March 31, 2022

While I was reading a book, I found this example.

def apply_discount(product, discount):
    price = int(product['price'] * (1.0 - discount))
    assert 0 <= price <= product['price']
    return price

I never saw the syntax 0 <= price <= product['price'] before, and it’s clear that here it’s testing the price, which should >= 0 and <= product['price']. I tested the function and it works as expected. I want to do more testing about the syntax 0 <= price <= product['price'].

a = 7
if 0 << a << 10:
    print('a is greater than or equal to 0 and less than or equal to 10')
else:
    print('a is not greater than or equal to 0 and less than or equal to 10')

It always prints a is not greater than or equal to 0 and less than or equal to 10. Why does it happen? What exactly does 0 << a << 10 work?

>Solution :

<< is a shift operator, you need to use < or <=:

a = 7
if 0 <= a <= 10:
    print('a is greater than or equal to 0 and less than or equal to 10')
else:
    print('a is not greater than or equal to 0 and less than or equal to 10')