Arithmetic Operators in Python

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There's nothing magical about arithmetic operators For example: >>> my_numbers * 2 returns the same as: >>> my_numbers.__mul__(2) `.__mul__()` is the special method which defines what multiplication using * does But, this can be misleading. There's a bit more happening…

For example, you can achieve the same multiplication of a list by reversing the operands: >>> 2 * my_numbers [2, 4, 6, 2, 4, 6] But, this is _not_ the same as calling `.__mul__()` directly

Note there's a space between the `2` and `.__mul__()` to avoid syntax issues This returns `NotImplemented` and not the same result as `2 * my_numbers`

The result from `2 * my_numbers` is actually returned by: `my_numbers.__rmul__(2)` >>> my_numbers.__rmul__(2) [2, 4, 6, 2, 4, 6]

Let's look at `2 * my_numbers` The reflected multiplication special method `.__rmul__()` of the operand on the right (`my_numbers`) is called if the `.__mul__()` method of the left operand (`2`) returns `NotImplemented`

I've written more about this in the inaugural article on The Python Coding Stack in April And there are more examples with `.__rmul__()` and `.__radd__()`, and more detailed explanation in the article You can get to The Stack through my bio here…