Function Definition with Specific Parameters

When you define a function like this:

def greet(name, age):
    print(f"Hello {name}, you are {age} years old!")

This function explicitly expects two positional arguments, name and age. There are two ways you can call this function:

1. Passing Positional Arguments:

greet("John", 12)

Here:

• name = "John"
• age = 12

Passing Keyword Arguments:

greet(name="John", age=12)

Here, you explicitly specify which value corresponds to which parameter.

What Happens if You Try to Pass a Dictionary Directly?

If you try to pass a dictionary directly like this:

greet({"name": "John", "age": 12})

It will cause an error because the function expects name and age as individual arguments, not as a single dictionary.

How to Pass a Dictionary Instead?

If you want to pass a dictionary like {"name": "John", "age": 12} into this function, you need to unpack it using the ** operator.

params = {"name": "John", "age": 12}
greet(**params)

This unpacks the dictionary so that it is equivalent to:

greet(name="John", age=12)

output
Hello John, you are 12 years old!

Why Does This Work?

The ** operator tells Python to treat the keys in the dictionary as the parameter names and their corresponding values as the arguments.

Without **, Python assumes the entire dictionary is a single positional argument, which doesn’t match the function signature.

How to Handle a Dictionary Directly?

If you want the function to accept a dictionary directly, you need to design it accordingly:

Example:

def greet(data):
    print(f"Hello {data['name']}, you are {data['age']} years old!")

Now you can call the function like this:

greet({"name": "Azeem", "age": 12})

output:
Hello Azeem, you are 12 years old!

Key Differences:

Scenario	Syntax	Use Case
Individual arguments expected	greet("Azeem", 12)	When you have explicit values for each parameter.
Keyword arguments expected	greet(name="Azeem", age=12)	When you want to be explicit about which value maps to which parameter.
Passing a dictionary	greet(**{"name": "Azeem", "age": 12})	When you have a dictionary and want to unpack it into keyword arguments.
Function designed for dict	greet({"name": "Azeem", "age": 12})	When the function is explicitly designed to handle dictionaries as input.

Conclusion

• If your function expects specific arguments (name and age), you can call it with positional or keyword arguments.
• To pass a dictionary into such a function, use ** to unpack it.
• If you want to pass a dictionary without unpacking, you need to design your function to handle it.