Python Reading, Updating, and Deleting Dictionary Entries

A profile can change a city and remove an outdated phone number.

What You Need to Understand

Dictionaries support reading with [] or get(), updating existing keys by assignment, adding new keys, and deleting keys with del or pop(). Choose the operation based on missing-key behavior.

When to Use It

A profile can change a city and remove an outdated phone number.

Step-by-Step Python Example

profile = {"name": "Noa", "city": "Tel Aviv", "phone": "123"}
profile["city"] = "Haifa"
profile["email"] = "[email protected]"
removed_phone = profile.pop("phone", None)
print(removed_phone)
print(profile)

How the Example Works

Assigning to city updates it, email adds a key, and pop() removes phone while returning its previous value.

Example Output

123
{'name': 'Noa', 'city': 'Haifa', 'email': '[email protected]'}
none

A Second Example

Compare this smaller variation with the main example, then experiment with your own values.

record = {"qty": 5}
record["qty"] += 1
print(record.pop("note", "none"))

Important Behavior and Edge Cases

Using del profile["missing"] raises KeyError. A supplied pop() default avoids it when absence is expected.

Try It Yourself

Update a stock quantity and safely remove an optional field.

Common Beginner Mistakes

Using del profile["missing"] raises KeyError. A supplied pop() default avoids it when absence is expected.
Treating missing dictionary keys, replacement precedence, and shallow copies as if they had identical behavior in every context.

Key Takeaways

Dictionaries support reading with [] or get(), updating existing keys by assignment, adding new keys, and deleting keys with del or pop().
Assigning to city updates it, email adds a key, and pop() removes phone while returning its previous value.
Using del profile["missing"] raises KeyError.