Last updated on June 3rd, 2025 at 10:23 am
If you've ever wondered why Python is so popular with beginners, one big reason is how easy it makes things, especially with something called Python functions.
These handy little tools allow you to write code once and reuse it as often as needed. That means less typing, fewer mistakes, and more time actually solving problems.
Whether you're learning Python from scratch or trying to polish your skills, this blog will walk you through everything you need to know. Get to know about functions in a way that’s simple and real-world friendly.
What is a Python function?
In simple words, a function is a set of instructions grouped under a single name. In Python, when you need that set of instructions, you just call the function instead of writing the code again.
Instead of copying the same chunk of code again and again, you just write it once inside a function. They can take inputs (parameters), process them, and return outputs. Then, whenever you need it, you call the function by its name. That’s it.
A basic function in Python looks like this:
| def greet():
print("Hello, World!") greet() # Output: Hello, World! |
We use the def keyword to define a new Python function. The name after that is what you'll use to call it later.
Why Use Functions in Python?
Functions make life easier in coding. Here’s why they’re important:
- Saves time: Write once, reuse multiple times.
- Cleaner code: Break large tasks into smaller, manageable blocks.
- Easy to manage: Structured code is easier to understand.
- Better structure: Fixing errors is simpler when code is modular.
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Types of Functions in Python
Python has different types of functions, each serving a unique purpose.
Built-in Functions:
These are Python functions that come pre-installed with Python, such as:
- print(): Displays output
- len(): Returns length of an object
- sum(): Adds up numbers in an iterable
User-Defined Functions:
These are functions you create yourself, specific to your needs. For example:
| def add_numbers(a, b):
return a + b print(add_numbers(3, 5)) # Output: 8 |
Other classifications include:
- Lambda functions: Short, anonymous functions written in one line. It can have multiple arguments but only one expression.
- Recursive functions: Functions that call themselves.
- Higher-order functions: Functions that take another function as an argument.
If you’re serious about writing clean and efficient code, learning the types of functions in Python is a must. Lambda functions in Python, especially, are super useful in data filtering.
Understanding Python List Functions
Lists are one of Python’s most flexible data types. And there’s a whole set of Python list functions to help you manage them easily.
Here are some common ones:
| Function | Description | Example |
| append() | Adds an item to the list | lst.append(5) |
| remove() | Removes an item from the list | lst.remove(3) |
| sort() | Sorts the list in order | lst.sort() |
| reverse() | Reverses the list order | lst.reverse() |
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Python Functions: Filter Function
The Python filter function helps you sift through lists or other sequences and keep only the elements that match a rule. It is ideal when you need to apply logic to data and hold only what you need.
You use it like this:
- Provide a function that describes the rule.
- Pass the list or sequence you want to filter.
Here’s an example that keeps only even numbers:
| numbers = [1, 2, 3, 4, 5, 6]
even_numbers = list(filter(lambda x: x % 2 == 0, numbers)) print(even_numbers) # Output: [2, 4, 6] |
Python Functions: Mod Function
The symbol % represents the Python mod function. It’s used to get the remainder after dividing two numbers.
For example:
| print(10 % 3) # Output: 1 |
That’s because 10 divided by 3 leaves a remainder of 1. This function is useful when you're writing loops or conditions, like checking if a number is even or odd.
Common Mistakes to Avoid
If you’re new to Python, it’s easy to slip up with the Python functions usage. Being aware of all of them will save you hours of confusion. Here are some mistakes people often make:
- Skipping function use: Writing everything in one block instead of modularising it.
- Forgetting to return values: If your function doesn’t return anything, it won’t give any result back.
- Not understanding scope: Variables created inside a function aren’t visible outside it unless you return them.
Executive Programs Offering Python
Python isn’t just for hobby projects anymore. Many of today’s top programmes are teaching it as a critical skill. Some of the best data science courses that include Python functions in their syllabuses are:
- Oxford Cybersecurity for Business Leaders Programme
- IIM Lucknow Executive Programme in AI for Business
- Advanced Certificate Program in Generative AI in Association with E&ICT Academy, IIT Guwahati
- Generative AI for Managers in Association with PwC Academy
- Postgraduate Program in Data Science and Analytics
Final Thoughts
As the world keeps running on data, becoming a data scientist can be a bright career path for you. Learning Python functions well will make coding easier and more efficient. However, the real learning happens when you start using them in real projects.
Python functions are the secret to writing better Python code. The more you practice using functions in real coding projects, the faster you'll improve.
So, start small, build real stuff, and you’ll be surprised how far a solid grasp of types of functions in Python can take you.
FAQs
- What is the main difference between built-in and user-defined functions in Python?
Built-in ones are ready to use from the start. User-defined functions are the ones you write for your own tasks.
- Can I change a global variable from inside a Python function?
Yes, but you need to declare it as global within the function. Otherwise, you’re just creating a local version.
- Does Python support function overloading?
Not in the traditional way. Instead, you can use default arguments or handle multiple input types in the same function.
- What are decorators in Python?
Decorators are like wrappers that add extra features to your functions, like logging or checking user access. You can add these without changing the actual code.
- Can I return more than one value from a function?
Absolutely. You can return multiple values using commas, and Python will bundle them into a tuple.
- What’s the difference between parameters and arguments?
Parameters are the placeholders in the function definition. Arguments are the real values you pass when calling the function.
- How does recursion work in Python?
Recursion is when a function calls itself to solve smaller pieces of a bigger problem. Just make sure to add a stopping point, or it’ll run forever.
