In most programming languages like Python, Java, or JavaScript, two important terms often come to use are **First-Class Functions** and **Higher-Order Functions**. These concepts are fundamental to understanding the flexibility and power of programming. Hence, in this tutorial, we will explore the differences between first-class functions and higher-order functions.

**Must Read:**

1. Higher Order Functions in Python

2. What are Lambda Functions in Python?

3. How to Use Lambda Function in Python?

4. Python Sort Using Lambda With Examples

5. Python Sort List of Lists With Examples

6. Python Get Last Element in List

7. How Do You Filter a List in Python?

## TOC – First-Class vs Higher-Order Functions

Before we dive into the tutorial, make sure you have a basic understanding of functions in Python. If you need a refresher, check out some introductory materials on functions in Python.

### First-Class Functions

#### What are First-Class Functions?

In Python, functions are considered first-class citizens. But what does that mean? Simply put, it means that functions in Python are treated as first-class objects, just like any other object such as integers, strings, or lists.

#### Characteristics

Here are the characteristics of first-class functions:

**Assigning to a Variable:**You can assign a function to a variable, just like you would with any other object.

```
def msg(txt):
return f"Hello, {txt}!"
my_msg = msg
print(my_msg("First-Class Function!"))
```

In this example, `my_msg`

now refers to the same function as `msg`

.

**Passing as an Argument:**Functions can be passed as arguments to other functions.

```
def calc(func, num):
return func(num, 2)
result = calc(pow, 5)
print(result)
```

Here, the `pow`

function is passed as an argument to `calc`

. It returns the square of the input number.

**Returning from a Function:**Functions can also be returned from other functions.

```
def get_msg():
def msg(txt):
return f"Hello, {txt}!"
return msg
my_msg = get_msg()
print(my_msg("First-Class Function"))
```

The function get_msg returns another function, creating a closure.

### Higher-Order Functions

#### What are Higher-Order Functions?

While first-class functions focus on the treatment of functions as objects, higher-order functions take things a step further. A higher-order function is a function that either takes one or more functions as arguments or returns a function as a result.

#### Characteristics

Let’s explore the characteristics of higher-order functions. We are demonstrating here with the help of examples of higher-order functions in Python.

**Taking a Function as an Argument:**A higher-order function can take another function as an argument.

```
def operate_on_list(nums, operation):
return [operation(num, 2) for num in nums]
sqrd_nums = operate_on_list([1, 2, 3, 4], pow)
print(sqrd_nums)
```

The `operate_on_list`

function takes a list of numbers and a function (`pow`

in this case) to apply to each element.

**Returning a Function:**A higher-order function can also return a function as its result.

```
def get_multiplier(factor):
def multiplier(number):
return number * factor
return multiplier
double = get_multiplier(2)
print(double(2))
```

The function `get_multiplier`

returns another function (`multiplier`

), creating a closure.

### Key Differences

Now that we’ve explored both first-class functions and higher-order functions, let’s highlight the key differences between them.

**Focus on Properties:**

**First-Class Functions:**Emphasizes the properties of functions as objects.**Higher-Order Functions:**Emphasizes functions that take or return other functions.

**Purpose:**

**First-Class Functions:**treats functions as if they are data, allowing storage, passing as arguments, and returning as values in Python**Higher-Order Functions:**Deals with functions that either team up with other functions or give birth to new functions.

**Usage:**

**First-Class Functions:**Commonly appears in scenarios where variables storing functions or functions appear as arguments. It is an exercise to discover the versatility of functions.**Higher-Order Functions:**Frequently used when dealing with operations on functions, providing a way to abstract behavior.

### Table of Comparison

Here is a one-to-one comparison between the two types of functions.

Feature | First-Class Functions | Higher-Order Functions |
---|---|---|

Assign to Variables | Functions can be stored in variables. | Functions can also be stored in variables. They often work with functions as inputs or outputs. |

Pass as Arguments | Functions can be given as inputs to other functions. | Higher-order functions mainly deal with passing functions as inputs. |

Return from Functions | Functions can be the output of another function. | Higher-order functions specifically return functions as outputs. |

Function as Parameter | Functions can take other functions as parameters. | Functions designed to take functions as parameters are called higher-order functions. |

Function as Result | Functions can be the result of another function. | Functions designed to return functions as results are higher-order functions. |

Example | Store a function in a variable. | Apply a function to values in another function. |

Give a function as an input. | Map a function to items in a list. | |

Get a function as an output. | Filter elements in a list based on a condition. |

This simplified version aims to provide a clear and concise understanding of the key differences between first-class functions and higher-order functions.

### Putting it into Practice

Now, let’s illustrate these concepts with a practical example. Imagine you are building a simple calculator program.

```
def square(num):
return num ** 2
def cube(num):
return num ** 3
def operate_on_list(nums, operation):
return [operation(num) for num in nums]
nums = [3, 7, 11, 17]
sqrd_nums = operate_on_list(nums, square)
cubed_nums = operate_on_list(nums, cube)
print("Original Numbers:", nums)
print("Squared Numbers:", sqrd_nums)
print("Cubed Numbers:", cubed_nums)
```

In this example, `operate_on_list`

is a higher-order function that takes a list of numbers and an operation function. The operation function can be `square`

or `cube`

, showcasing the concept of passing functions as arguments.

## Conclusion

Understanding first-class functions and higher-order functions in Python is essential for writing clean, modular, and efficient code. First-class functions enable treating functions as objects, providing flexibility in their use. Higher-order functions, on the other hand, take this flexibility to the next level. They allow other functions to appear as arguments or returned as results.

By grasping these concepts, you are now in a better position to design robust solutions in Python or Java. Experiment with these ideas in your code, and you’ll discover the true power of functions in Python programming.

**Happy Coding,Team TechBeamers**