Variable-length keyword arguments (**kwargs) in Python - Step-by-Step Execution

Concept Flow - Variable-length keyword arguments (**kwargs)

Function called with named arguments

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Collect all extra named args into kwargs dict

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Inside function: kwargs is a dict

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Use kwargs keys and values as needed

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Function completes and returns

When a function is called with extra named arguments, Python collects them into a dictionary called kwargs inside the function.

Execution Sample

Python

def greet(**kwargs):
    for key, value in kwargs.items():
        print(f"{key}: {value}")

greet(name='Alice', age=30)

This code collects extra named arguments into kwargs and prints each key and value.

Execution Table

Step	Action	kwargs content	Output
1	Function greet called with name='Alice', age=30	{} (before collection)
2	Collect extra named arguments into kwargs	{'name': 'Alice', 'age': 30}
3	Start loop over kwargs.items()	{'name': 'Alice', 'age': 30}
4	First iteration: key='name', value='Alice'	{'name': 'Alice', 'age': 30}	name: Alice
5	Second iteration: key='age', value=30	{'name': 'Alice', 'age': 30}	age: 30
6	Loop ends, function ends	{'name': 'Alice', 'age': 30}

💡 All items in kwargs processed, function returns None

Variable Tracker

Variable	Start	After Step 2	After Step 4	After Step 5	Final
kwargs	{}	{'name': 'Alice', 'age': 30}	{'name': 'Alice', 'age': 30}	{'name': 'Alice', 'age': 30}	{'name': 'Alice', 'age': 30}
key	N/A	N/A	'name'	'age'	N/A
value	N/A	N/A	'Alice'	30	N/A

Key Moments - 3 Insights

Why is kwargs a dictionary and not a list or other type?

Because **kwargs collects named arguments as key-value pairs, so Python stores them in a dictionary as shown in execution_table step 2.

What happens if no extra named arguments are passed?

kwargs will be an empty dictionary {} and the loop inside the function will not run, so no output is produced (see variable_tracker start state).

Can kwargs keys be accessed like normal dictionary keys?

Yes, inside the function kwargs behaves like a normal dictionary, so you can use methods like items() or access keys directly.

Visual Quiz - 3 Questions

Look at the execution_table at step 4, what is the value of key and value?

A key='Alice', value='name'

B key='age', value=30

C key='name', value='Alice'

D key='age', value='Alice'

💡 Hint

Check execution_table row with Step 4 under 'Action' and 'Output' columns.

At which step does kwargs get filled with the passed named arguments?

A Step 2

B Step 1

C Step 3

D Step 6

💡 Hint

Look at execution_table row Step 2 where kwargs content changes from empty to filled.

If greet() is called with no arguments, what will kwargs be inside the function?

A A dictionary with keys 'name' and 'age'

B An empty dictionary {}

C None

D A list of arguments

💡 Hint

Refer to key_moments answer about no extra named arguments and variable_tracker start state.

Concept Snapshot

def func(**kwargs):
  # kwargs is a dict of extra named args
  for key, value in kwargs.items():
    print(f"{key}: {value}")

Use **kwargs to accept any number of named arguments.
Inside the function, kwargs behaves like a dictionary.

Full Transcript

This example shows how Python collects extra named arguments passed to a function into a dictionary called kwargs. When greet(name='Alice', age=30) is called, kwargs becomes {'name': 'Alice', 'age': 30}. The function loops over this dictionary and prints each key and value. If no extra named arguments are passed, kwargs is empty. This helps functions accept flexible named inputs.