Why Does Integer Division in Python Sometimes Produce Unexpected Rounded Results?

Integer Division in Python: Unraveling the Mystery of Rounded Results

In Python, division operations can sometimes yield unexpected outcomes, particularly when the operands are integers. To understand this behavior, we must delve into the nuances of Python's integer division.

When two integers are divided, the result is also an integer. This behavior arises from Python 2.x's implementation of division, where the operands are truncated before the operation is performed. Consider the example:

>>> (20-10) / (100-10)
0

Here, the operands evaluate to 10 and 90, respectively. Since both are integers, the result is also truncated to 0. This is because the division operator (/) in Python 2.x always results in an integer.

To resolve this issue, one can enforce float division by casting one of the operands to a float:

>>> (20-10) / float((100-10))
0.1111111111111111

Alternatively, you can import the division module from __future__:

>>> from __future__ import division
>>> (10 - 20) / (100 - 10)
-0.1111111111111111

This ensures that division always returns a float, regardless of the operand types. By understanding these subtleties, you can avoid unexpected rounding errors in your Python code.

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