L4.10: Types of Function Arguments

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Learning outcomes

• distinguish positional and keyword arguments
• use default arguments correctly
• understand *args and **kwargs at introductory level

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Positional arguments

def introduce(name, age):
    print(name, age)

introduce("Riya", 19)

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Keyword arguments

introduce(age=19, name="Riya")

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Default arguments

def greet(name, msg="Hello"):
    print(msg, name)

greet("Asha")
greet("Asha", "Hi")

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Variable-length positional arguments

def add_all(*nums):
    total = 0
    for x in nums:
        total += x
    return total

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Variable-length keyword arguments

def show_info(**data):
    print(data)

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Common rules

• positional arguments must come before keyword arguments in function call
• default arguments should be placed after required ones in definition

# def f(x=1, y):   # invalid

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Exam hints and traps

• missing required argument raises TypeError
• too many arguments also raise TypeError
• default value is used only when caller does not supply that argument

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Quick practice

1. Write function with default argument country="India".
2. Call a function once with positional and once with keyword style.
3. Explain what *nums collects.