Basic Built-in Functions and Creating Your Own Functions in Python

Python provides a variety of built-in functions that make it easy to perform common tasks. Additionally, you can create your own functions to encapsulate reusable pieces of code. Let's explore some of the basic built-in functions and learn how to create custom functions.

Basic Built-in Functions

print()

The print() function outputs text or other data to the console.

print("Hello, World!")
print(42)
print(3.14)

type()

The type() function returns the data type of a variable or value.

print(type("Hello"))  
# <class 'str'>
print(type(42))       
# <class 'int'>
print(type(3.14))     
# <class 'float'>

len()

The len() function returns the number of items in a container, such as a string, list, or dictionary.

print(len("Hello"))            
# 5
print(len([1, 2, 3, 4, 5]))    
# 5
print(len({"name": "Alice"}))  
# 1

max() and min()

The max() function returns the largest item in an iterable or the largest of multiple arguments. The min() function returns the smallest item.

print(max(1, 2, 3, 4, 5))  
# 5
print(min(1, 2, 3, 4, 5))  
# 1
print(max([1, 2, 3]))      
# 3
print(min([1, 2, 3]))     
# 1

sum()

The sum() function returns the sum of all items in an iterable.

print(sum([1, 2, 3, 4, 5]))  
# 15
print(sum((1, 2, 3)))        
# 6

input()

The input() function reads a string from user input.

name = input("Enter your name: ")
print("Hello, " + name + "!")

Creating Your Own Functions

You can create your own functions to encapsulate reusable pieces of code. This helps in organizing and managing your code better.

Defining a Function

Use the def keyword to define a function, followed by the function name and parentheses. Inside the parentheses, you can specify parameters. The function body is indented.

def greet(name):
    print("Hello, " + name + "!")

Calling a Function

Call the function by using its name followed by parentheses. If the function requires parameters, provide them inside the parentheses.

greet("Alice")  
# Output: Hello, Alice!
greet("Bob")    
# Output: Hello, Bob!

Function with Return Value

A function can return a value using the return statement.

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

result = add(3, 4)
print(result)  
# Output: 7

Function with Default Parameters

You can provide default values for parameters. If no argument is passed, the default value is used.

def greet(name="Guest"):
    print("Hello, " + name + "!")

greet("Alice")  
# Output: Hello, Alice!
greet()         
# Output: Hello, Guest!

Function with Variable Number of Arguments

Use *args to allow a function to accept any number of positional arguments, and **kwargs to accept keyword arguments.

def print_numbers(*args):
    for number in args:
        print(number)

print_numbers(1, 2, 3, 4)  
# Output: 1 2 3 4

def print_info(**kwargs):
    for key, value in kwargs.items():
        print(f"{key}: {value}")

print_info(name="Alice", age=25)  
# Output: name: Alice age: 25

Summary

• Built-in Functions: print(), type(), len(), max(), min(), sum(), input()
• Defining Functions: Use def to define a function, provide parameters if needed.
• Calling Functions: Use the function name followed by parentheses, providing arguments if required.
• Return Values: Use return to send back a result from a function.
• Default Parameters: Provide default values for parameters.
• Variable Arguments: Use *args for positional arguments and **kwargs for keyword arguments.

Understanding and using functions effectively allows you to write modular, reusable, and organized code. Practice creating and calling your own functions to get comfortable with this fundamental concept in Python.