First class objects in a language are handled uniformly throughout. They may be stored in data structures, passed as arguments, or used in control structures. A programming language is said to support first-class functions if it treats functions as first-class objects. Python supports the concept of First Class functions.
Properties of first class functions:
- A function is an instance of the Object type.
- You can store the function in a variable.
- You can pass the function as a parameter to another function.
- You can return the 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 are assigning function to a variable. This assignment doesn’t call the function. It takes the function object referenced by shout and creates a second name pointing to it, yell.
# Python program to illustrate functions# can be treated as objectsdef shout(text): return text.upper() print (shout('Hello')) yell = shout print (yell('Hello')) |
Output:
HELLO HELLO
2. Functions can be passed as arguments to other functions: Because functions are objects we can pass them as arguments to other functions. Functions that can accept other functions as arguments are also called higher-order functions. In the example below, we have created a function greet which takes a function as an argument.
# Python program to illustrate functions# can be passed as arguments to other functionsdef 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 AM CREATED BY A FUNCTION PASSED AS AN ARGUMENT. hi, i am created by a function passed as an argument.
3. Functions can return another function: Because functions are objects we can return a function from another function. In the below example, the create_adder function returns 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
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