The inbuilt **`setdefault()` method** in Python is used to return the `value` of a `key` in a dictionary.

<h2>Syntax</h2>

```python
dict.setdefault(key, value)
```

<h2>Parameters and return value</h2>

The ```setdefault()``` method requires one parameter to be passed, which is the `key` of the corresponding `value` you want to return. 

In addition, an optional `value` parameter can be passed, which becomes the value of the `key`. This works if the provided `key` does not exist in the dictionary.

* If `key` exists in the dictionary, its corresponding value is returned. </li>
* If `key` doesn't exist in the dictionary, the provided `value` is returned. </li>
* If `key` doesn't exist in the dictionary, and `value` isn't provided, the method returns `None`.

#When the provided key exists in the dictionary

postcodes = dict({'griffith':2603, 'belconnen':2617, 'phillip':2606, 'civic':2601})

civic_code = postcodes.setdefault('civic')
print("The postcode of Civic is:", civic_code)

#When the provided key doesn't exist in the dictionary and
#value is provided

postcodes = dict({'griffith':2603, 'belconnen':2617, 'phillip':2606})

civic_code = postcodes.setdefault('civic', 2601)
print("The postcode of Civic is:", civic_code)

#When the provided key doesn't exist in the dictionary and
#value isn't provided

postcodes = dict({'griffith':2603, 'belconnen':2617, 'phillip':2606})

civic_code = postcodes.setdefault('civic')
print("The postcode of Civic is:", civic_code)

How setdefault() works in Python

Used in Python to return a dictionary key's value, adding it with an optional default if absent.

How setdefault() works in Python

Syntax

Parameters and return value

Example #1

Example #2

Example #3