Why does bit-wise shift left return different results in Python and Java?

Question

I'm trying to port some functionality from a Java app to Python.

In Java,

System.out.println(155 << 24);

Returns: -1694498816

In Python:

print(155 << 24)

Returns 2600468480

Many other bitwise operations have worked in the same way in both languages. Why is there a different result in these two operations?

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EDIT: I'm trying to create a function in python to replicate how the left shift operator works in Java. Something along the lines of:

def lshift(val, n):
    return (int(val) << n) - 0x100000000

However this doesn't seem right as (I think) it turns all numbers negatives?

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EDIT2: Several hours later, I've decided it is probably not the best idea to use Python for this job and will take part of the Java application and use it as a micro service for the existing Python app.

Answer 1

Java has 32-bit fixed width integers, so 155 << 24 shifts the uppermost set bit of 155 (which is bit 7, counting bits from zero, because 155 is greater than 2⁷ but less than 2⁸) into the sign bit (bit 31) and you end up with a negative number.

Python has arbitrary-precision integers, so 155 << 24 is numerically equal to the positive number 155 × 2²⁴