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Python Functions

·309 words·2 mins·
Programming Python Functions Programming
Table of Contents

Python Functions
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A function is a block of organized, reusable code that is used to perform a single, related action. Functions provide better modularity for your application and a high degree of code reusing.

Defining a Function
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You can define a function using the def keyword.

def greet(name):
    """This function greets the person passed in as a parameter."""
    print(f"Hello, {name}!")

# Calling the function
greet("Alice")  # "Hello, Alice!"

Arguments
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Information can be passed into functions as arguments. Arguments are specified after the function name, inside the parentheses.

Positional and Keyword Arguments
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def describe_pet(animal_type, pet_name):
    """Display information about a pet."""
    print(f"I have a {animal_type}.")
    print(f"My {animal_type}'s name is {pet_name.title()}.")

# Positional arguments
describe_pet("hamster", "harry")

# Keyword arguments
describe_pet(pet_name="willie", animal_type="dog")

Default Arguments
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def describe_pet(pet_name, animal_type="dog"):
    """Display information about a pet with a default animal type."""
    print(f"I have a {animal_type}.")
    print(f"My {animal_type}'s name is {pet_name.title()}.")

describe_pet("willie")  # Uses the default animal_type "dog"

Arbitrary Arguments
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If you do not know how many arguments will be passed into your function, you can use *args for non-keyword arguments and **kwargs for keyword arguments.

def make_pizza(*toppings):
    """Print the list of toppings that have been requested."""
    print(toppings)

make_pizza("pepperoni")
make_pizza("mushrooms", "green peppers", "extra cheese")

def build_profile(first, last, **user_info):
    """Build a dictionary containing everything we know about a user."""
    profile = {"first_name": first, "last_name": last}
    for key, value in user_info.items():
        profile[key] = value
    return profile

user_profile = build_profile("albert", "einstein",
                             location="princeton",
                             field="physics")
print(user_profile)

Lambda Functions
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A lambda function is a small anonymous function. A lambda function can take any number of arguments, but can only have one expression.

# A lambda function that adds 10 to the number passed in as an argument
x = lambda a: a + 10
print(x(5))  # 15

# A lambda function that multiplies two arguments
multiply = lambda x, y: x * y
print(multiply(5, 6))  # 30

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