Frequently Asked Questions

When do we need this?

dowhen serves well in these scenarios:

1. monkeypatching:

dowhen allows you to inject code at specific points in your application without modifying the original codebase. When you need to change the behavior of stdlib or third-party libraries, you can use dowhen to do it to avoid vendoring your own version or swapping the whole function.

2. debugging:

dowhen is just like a debugger - it can print stuff or execute code at specific points in your code to help you understand what is going on. Unlike a debugger, it is easily reproducible - you don’t need to type commands in a terminal.

3. logging:

dowhen can be used to log all kinds of stuff without adding extra code to your application.

Is the overhead high?

Not at all. dowhen utilizes sys.monitoring so it only triggers events when necessary. It has minimal impact on performance.

Why 3.12+?

dowhen uses the new sys.monitoring module introduced in Python 3.12.