Python Lambda Function
Python Lambda function is a single line function whose body is just an expression and can accept multiple arguments.
In this tutorial, we shall first learn the basics of lambda function and secondly some interesting hacks that we can do with these lambda functions.
Syntax of Lambda Function
Following is the syntax of Lambda Function.
lambda arguments : expression
You can assign this lambda function to a variable. Something like in below code snippet.
x = lambda arguments : expression
And you can call the lambda function with the variable name x. Following is an example code snippet to call the lambda function.
result = x(arguments)
The arguments are passed just like a regular function’s arguments, but the function name being the variable we assigned this lambda function to.
When you call a lambda function, the expression is evaluated and the evaluated value is returned. So, you have the arguments, body and return statement, everything in just a line. So very concise.
Example 1: Python Lambda Function
Following is a simple lambda function, that takes a number and returns the square of it.
#lambda function square = lambda a: a*a #call lambda function result = square(6) print(result)
Example 2: Python Lambda Function – Multiple arguments
We already mentioned that a Python Lambda function can accept multiple arguments. In the following example, we define a lambda function with two arguments, say a and b, and we shall multiplication of a and b.
#lambda function mul = lambda a,b: a*b #call lambda function result = mul(5,3) print(result)
Example 3: Python Lambda Function with No Arguments
Yeah! You can define a lambda function with no arguments at all. If there were to be requirement that you create a lambda function with no arguments, you can.
In the following example, we define a lambda function with no arguments, and returns
6 when called.
#lambda function six = lambda : 6 #call lambda function result = six() print(result)
Recursive Lambda Function
You can design a recursion function using lambda function. According to the syntax of Python Lambda function, all that you need is an expression that evaluates to a single value to return. So, if you can build a recursive function satisfying this criteria, you have a recursive lambda function.
In the following example, we defined a lambda function that can calculate the factorial of a given number, using recursion.
#recursive lambda function factorial = lambda a: a*factorial(a-1) if (a>1) else 1 #call lambda function result = factorial(5) print(result)
Return Lambda Function
Lambda Function is just like a variable. So, you can return a lambda function from another function.
import math #function returning lambda function def myfunc(n): return lambda a : math.pow(a, n) #lambda functions square = myfunc(2) #square = lambda a : math.pow(a, 2) cube = myfunc(3) #cube = = lambda a : math.pow(a, 3) squareroot = myfunc(0.5) #squareroot = lambda a : math.pow(a, 0.5) print(square(3)) print(cube(3)) print(squareroot(3))
9.0 27.0 1.7320508075688772
Concluding this tutorial of Python Examples, we learned how to define a lambda function, and use it in your program constructively, with the help of example programs.