python: unintentionally modifying parameters passed into a function

Question

A few times I accidentally modified the input to a function. Since Python has no constant references, I\'m wondering what coding techniques might help me avoid making this mista

Answer 1

There is a best practice for this, in Python, and is called unit testing.

The main point here is that dynamic languages allows for much rapid development even with full unit tests; and unit tests are a much tougher safety net than static typing.
As writes Martin Fowler:

The general argument for static types is that it catches bugs that are otherwise hard to find. But I discovered that in the presence of SelfTestingCode, most bugs that static types would have were found just as easily by the tests.