Python for Data Analytics • Lesson 16
Functions
Learn how to create reusable blocks of Python code using functions. Work with parameters, arguments, return values, default parameters and practical data analytics examples.
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What Is a Function?
A function is a reusable block of code that performs one specific task. Instead of writing the same lines over and over, you name them once and call that name whenever you need them.
Learn by Seeing
Wrap a task in a name
def greet():
print("Hello!")
greet()def gives the block a name; the name becomes the way to run it.
Interactive Activity
What is the main advantage of a function?
Hint: The point is to write once and call many times.
Python Analyst Mindset
Functions turn one-off work into tools
Once a calculation matters, wrap it in a function. The formula lives in one place, gets a name you can read, and can be called hundreds of times with different data — without ever copying the math.
Define
Name the task with def.
Parameterize
Pass inputs at call time.
Return
Hand the result back.
Reuse
Call it anywhere.
Lesson Summary
What you learned
Defines a function with a name.
name() runs the function body.
Parameters are names; arguments are the values you pass.
Hands a value back to the caller.
Fallback values when arguments are omitted.
Variables created inside a function stay inside it.