What is a first class function in Python

Question

I'm still confused by what first-class functions . If I understand correctly, first-class functions should use one function as an object. Is it correct?

Is this a first-class function ?

 def this_is_example(myarg1): return myarg1 def this_is_another_ example(myarg): return this_is_example(myarg)+myarg this_is_another_ example(1) 

Answer 1

A first-class function is not a special kind of function. All functions in Python are first-class functions. To say that functions are first-class in a certain programming language means that they can be transferred and manipulated in the same way as you pass and manipulate other kinds of objects (for example, whole or whole). You can assign a function to a variable, pass it as an argument to another function, etc. The difference is not that individual functions can be first-class or not, but all languages ​​can treat functions as first-class objects or not.

Answer 2

First Class Functions (FCFs) are functions that are referred to as so-called First Class Citizens (FCCs). FCC in a programming language are objects (the term "objects" is very freely used here), which:

• It can be used as a parameter
• May be used as return value
• Can be assigned to variables
• It can be stored in data structures such as hash tables, lists, ...

In fact, very crudely and simply, FCFs are variables of type 'function' (or variables that point to a function). You can do with them everything you can do with a “normal” variable.

Knowing this, both this_is_another_example(myarg) and this_is_example(myarg1) are first-class functions, since all functions are first-class in certain programming languages.

Answer 3

Not. You are talking about higher order functions - refer .

Functions of the first class: if a function can be assigned to a variable or passed as an object / variable to another function, this function is called as a function of the first class.

Python, JavaScript, and C (pointers) support first-class functions.

Simple example (in python):

 def square(x): return x * x def cube(x): return x * x * x def print_result(x, func): """recieve a function and execute it and return result""" return func(x) do_square = square # assigning square function to a variable do_cube = cube # assigning cube function to a variable res = print_result(5, do_square) # passing function to another function print res res = print_result(5, do_cube) print res 

This program is for illustration purposes only.

Answer 4

 def pie(r): def circleArea(d): return r * (d ** 2) return circleArea c = pie(3.14) print c(2) 

Above is an example of a first class function in python.

Answer 5

Each function in python is the first class, as they can be passed like any other object.

Answer 6

First Class Functions in Python

First-class objects in the language are handled the same everywhere. They can be stored in data structures, passed as arguments, or used in control structures. It is said that a programming language supports first-class functions if it considers functions as first-class objects. Python supports the concept of first-class functions.

Properties of functions of the first class:
A function is an instance of an object type.
- You can save the function in a variable. - You can pass a function as a parameter to another function. - You can return a function from a function. - You can store them in data structures such as hash tables, lists, ...

Examples illustrating first-class functions in Python
1. Functions are objects: Python functions are first class objects. In the example below, we assign a function to a variable. This assignment does not call a function. It takes the function object referenced by the scream, and creates a middle name that points to it, screaming.

 # Python program to illustrate functions # can be treated as objects def shout(text): return text.upper() print shout('Hello') yell = shout print yell('Hello') 

Output:
HI
HI

2. Functions can be passed as arguments to other functions: since functions are objects, we can pass them as arguments to other functions. Functions that can take other functions as arguments are also called higher-order functions. In the example below, we created a greet function that takes a function as an argument.

 # Python program to illustrate functions # can be passed as arguments to other functions def shout(text): return text.upper() def whisper(text): return text.lower() def greet(func): #storing the function in a variable greeting = func("Hi, I am created by a function passed as an argument.") print greeting greet(shout) greet(whisper) 

Output:
HI, I CREATED BY A FUNCTION PASSING AS AN ARGUMENT.
Hi, I am created by a function passed as an argument.

3. Functions can return another function: since functions are objects, we can return a function from another function. In the example below, the create_adder function returns an adder function.

 #Python program to illustrate functions #Functions can return another function def create_adder(x): def adder(y): return x+y return adder add_15 = create_adder(15) print add_15(10) 

Output:
25