Passing Dictionary as Arguments to Function in Python

Passing a dictionary as an argument to a function in Python allows you to work with structured data in a more flexible and efficient manner. For example, given a dictionary d = {"name": "Alice", "age": 30}, you can pass it to a function and access its values in a structured way. Let's explore the most efficient methods to pass a dictionary as an argument to a function.

Passing Dictionary as an argument

This is the most straightforward and efficient approach where you pass the entire dictionary to the function and process it inside the function.

def fun(d):
    for key in d:
        print("key:", key, "value:", d[key])
        
        
d1 = {'a': 1, 'b': 2, 'c': 3}
fun(d1)

key: a value: 1
key: b value: 2
key: c value: 3

Explanation: fun(d) accepts a dictionary d, iterates through its keys, accesses each corresponding value with d[key] and prints the key-value pair in the format "key: <key> value: <value>".

Using ** to unpack the dictionary

If you know the dictionary has specific keys that match function parameters, you can unpack the dictionary and pass the key-value pairs as keyword arguments.

def fun(**d):
    for key, value in d.items():
        print("key:", key, "Value:", value)

d1 = {'a': 1, 'b': 2, 'c': 3}
fun(**d1)

key: a Value: 1
key: b Value: 2
key: c Value: 3

Explanation: fun(**d) accepts keyword arguments, iterates through the passed key-value pairs using d.items() and prints each key-value pair in the format "key: <key> Value: <value>".

Modifying Dictionary Values

Dictionaries are mutable, meaning their values can be directly modified within a function. When a dictionary is passed as an argument to a function, changes to its values will persist outside the function scope.

def fun(p):
    p['age'] += 1

d = {'name': 'John Doe', 'age': 25}
fun(d)
print(d['age'])

26

Explanation: fun(d) updates the 'age' in the dictionary d, changing it from 25 to 26. Since dictionaries can be changed directly, the update is reflected outside the function too.

Using **kwargs

This approach uses **kwargs to accept any number of keyword arguments and prints them. This is a flexible approach, especially if the dictionary may have varying keys.

def fun(**kwargs):
    for key, value in kwargs.items():
        print("key:", key, "Value:", value)

d1 = {'a': 1, 'b': 2, 'c': 3}
fun(**d1)

key: a Value: 1
key: b Value: 2
key: c Value: 3

Explanation: fun(**kwargs) accepts keyword arguments and iterates through each key-value pair using kwargs.items(). By unpacking d1 using **d1, the dictionary d1 = {'a': 1, 'b': 2, 'c': 3} is passed as individual key-value pairs.

When to Use Dictionary as Arguments?

Passing a dictionary to a function is especially useful when you have a group of related parameters that need to be processed together. Some common scenarios include:

• Handling configurations where multiple settings (like database configurations, API configurations, etc.) are passed as a dictionary.
• Working with complex data structures where the function might need to handle multiple data points of different types and a dictionary provides a structured way to pass this information.

Related Articles

• dictionary
• functions
• **kwargs