Looking things up.
WHAT A DICTIONARY IS
A collection of keys, each with an associated value.
WHY THEY MATTER
Most real-world data is naturally key and value: a customer record, a configuration, a row from a file.
WHAT YOU DO WITH THEM
Look up a value by its key Add and remove entries Iterate over keys, values or both Check whether a key exists
THE MISSING KEY PROBLEM
Accessing a key that does not exist raises an error.
WHAT TO DO ABOUT IT
Use the method that returns a default when the key is absent, or check first.
That single habit prevents many failures.
NESTING
Dictionaries containing lists or other dictionaries.
How structured data such as JSON is represented.
WHAT TO BE CAREFUL WITH
Deeply nested structures, which become hard to read Assuming a key exists Keys differing only in case or whitespace
WHAT TO USE FOR STRUCTURED RECORDS
A dictionary for flexible data, or a defined class where the structure is fixed.
