What are some common mistakes when using dictionaries in Python?

What are some common mistakes when using dictionaries in Python?

Some common mistakes include using mutable types as dictionary keys, forgetting to use quotes for string keys, and not handling missing keys properly.

Can you explain why mutable types can't be used as keys?

Mutable types like lists can change, which makes them unhashable. Dictionary keys must be immutable to ensure consistent access.

What happens if I try to use a list as a key?

If you try to use a list as a key, Python will raise a TypeError, indicating that the list is unhashable.

How can I safely handle missing keys?

You can use the get() method to provide a default value or use defaultdict from the collections module for automatic defaults.

Are there any performance issues with dictionaries?

Yes, while dictionaries are generally fast, performance can degrade with very large datasets or if keys are not well-distributed.