Functions: Defining and Calling

Functions let us group reusable code under a name. This makes our code more organized and avoids repetition.

In Python, we define a function using the def keyword followed by the function name and parentheses.

Let’s go through the basics of creating and using functions.

Use def to define a function. Include parentheses (with or without parameters) and end the line with a colon.

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def greet():
    print("Hello, welcome!")

Explanation:

• This function is named greet.
• It has no parameters.
• When called, it prints a greeting.

Once defined, we can call the function by writing its name followed by parentheses.

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greet()

Explanation:

• This line runs the greet() function and prints the message.

Functions can take input values (parameters) to perform different actions based on the input.

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def greet_user(name):
    print("Hello,", name)

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greet_user("Alice")

Explanation:

• greet_user takes one argument called name.
• When called with "Alice", it prints: Hello, Alice.

Functions can send back (return) a result using the return statement.

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def add(a, b):
    return a + b

result = add(5, 3)
print(result)

Explanation:

• add takes two arguments and returns their sum.
• The result is stored in result and printed.

Next, you’ll learn how to pass arguments and handle return values in more detail — key to writing powerful Python functions.