Dealing With “Dictionary Changed Size During Iteration” In Python When Modifying a dict In-Place

The aim of this playbook🏁 is to idiomatically deal with Runtime Error: Dictionary changed size during iteration when modifying a dictionary in-place within a for a loop.

notes

• pass the items into a list constructor that creates an on-the-fly-list just for the loop
• modify in-place
• I am deleting a key in place in a structure loaded from a YAML file that will be later replace the same file

for key, _ in list(imgIndex.items()):
        if docID in key:
            del imgIndex[key]

links

• Filtering Dictionary In Python 3. “RuntimeError: Dictionary changed size… — codeburst