Learn Python Change Dictionary Items

Dictionaries in Python are mutable, which means you can change existing values, add new key–value pairs, and update multiple items at once.

This topic explains all correct ways to change dictionary items, with examples and best practices.

Change Value Using Key

You can change the value of an existing key by assigning a new value.

Change Value Using `update()`

The update() method can change one or more values.

Add New Item While Updating

If the key does not exist, update() adds it.

Change Dictionary Items Using Loop

Change Nested Dictionary Items

Change Value Safely Using `get()`

Change Keys (Indirect Way)

Dictionary keys cannot be changed directly. You must remove and reinsert.

Replace Entire Dictionary

Change Using Dictionary Comprehension

Common Mistakes

Using Index Instead of Key

Forgetting That Assignment Overwrites Value

Only the latest value remains.

Best Practices

Use direct assignment for single updates
Use update() for bulk changes
Use loops for conditional updates
Modify nested dictionaries carefully
Avoid changing keys unless necessary