pythonOtherMedium

Merging settings mutates the defaults

Time: 0:00

What it should do

merge_settings(defaults, overrides) should merge overrides on top of defaults without changing the defaults. It returns "mode|numberOfDefaultKeys" so you can see both.

What goes wrong

The key count reflects the merged result rather than the original defaults — merging a brand-new key into a one-key defaults dict reports 2 instead of 1.

Hints

This is a mutation and copying bugs bug

Assignment does not copy, a shallow copy still shares its contents, and mutating methods return None.

Learn the mutation and copying bugs pattern