Python Anonymous/Lambda Function

In this article, you’ll find out about the anonymous function, also called lambda functions. You’ll realize what they are, their syntax, and how to use them (with examples).

What are lambda functions in Python?

In Python, an anonymous function is a function that is characterized without a name.

While normal functions are characterized using the def keyword in Python, mysterious capacities are characterized using the lambda keyword.

Hence, anonymous functions are also called lambda functions.

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How to use lambda Functions in Python?

A lambda function in python has the following syntax.

Syntax of Lambda Function in python

lambda arguments: expression

Lambda functions can have any number of contentions yet just a single articulation. The articulation is assessed and returned. Lambda functions can be used wherever function objects are required.

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Example of Lambda Function in python

Here is an example of a lambda function that doubles the input value.

# Program to show the use of lambda functions
double = lambda x: x * 2

print(double(5))

Output

10

In the above program, lambda x: x * 2 is the lambda function. Here x is the argument and x * 2 is the expression that gets evaluated and returned.

This function has no name. It returns a function object which is assigned to the identifier double. We can now call it as a normal function. The statement

double = lambda x: x * 2

is nearly the same as:

def double(x):
   return x * 2

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Use of Lambda Function in python

We use lambda functions when we require a nameless function for a brief period of time.

In Python, we by and large use it as a contention to a higher-request work (a capacity that takes in different functions as arguments). Lambda functions are used alongside worked in functions likefilter(), map() etc.

Example use with filter()

The filter () function in Python takes in a function and a list as arguments.

The function is called with all the things in the rundown and another rundown is returned which contains things for which the function evaluates to True.

Here is an example use of filter () capacity to sift through just even numbers from a list.

# Program to filter out only the even items from a list
my_list = [1, 5, 4, 6, 8, 11, 3, 12]

new_list = list(filter(lambda x: (x%2 == 0) , my_list))

print(new_list)

Output

[4, 6, 8, 12]

Example use with map()

The map() function in Python takes in a function and a list.

The function is called with all the items in the list and a new list is returned which contains items returned by that function for each item.

Here is an example use of map() function to double all the items in a list.

# Program to double each item in a list using map()

my_list = [1, 5, 4, 6, 8, 11, 3, 12]

new_list = list(map(lambda x: x * 2 , my_list))

print(new_list)

Output

[2, 10, 8, 12, 16, 22, 6, 24]

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Please feel free to give your comment if you face any difficulty here.

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