{"id":79043,"date":"2020-06-10T13:11:17","date_gmt":"2020-06-10T07:41:17","guid":{"rendered":"https:\/\/techvidvan.com\/tutorials\/?p=79043"},"modified":"2020-06-10T13:11:17","modified_gmt":"2020-06-10T07:41:17","slug":"lambda-expression-in-python","status":"publish","type":"post","link":"https:\/\/techvidvan.com\/tutorials\/lambda-expression-in-python\/","title":{"rendered":"Lambda Expression in Python"},"content":{"rendered":"

Python\u2019s Lambda expression are quite controversial<\/strong> in the programming circles<\/strong>. Some find it elegant<\/strong> and useful<\/strong>, while others freak out with the name of it.<\/p>\n

By the end of this article, you will be able to decide for yourselves whether you want them to be a part of your code <\/strong>or not. We\u2019ll help you get a clear understanding of what Lambda functions\/ expressions<\/strong> are. Also, you\u2019ll learn why and how you should use them<\/strong> in your program<\/strong>.<\/p>\n

Let\u2019s look at how Lambda expressions<\/strong> fit into your code!<\/p>\n

What is Lambda function in Python?<\/h3>\n

Lambda functions are anonymous<\/strong> or nameless<\/strong>. Unlike traditional functions<\/strong>, lambda functions<\/strong> have no name<\/strong>. You can use anonymous functions<\/strong> when:<\/p>\n

a. You want to perform a simple operation<\/strong> and,<\/p>\n

b. You\u2019re going to use this<\/strong> function <\/strong>just once<\/strong>.<\/p>\n

Syntax of Python Lambda expression<\/strong><\/p>\n

lambda parameters: expression<\/strong><\/p>\n

The syntax of lambda expression contains three parts:<\/p>\n

    \n
  • lambda<\/strong> – This is the keyword used to create<\/strong> a lambda function<\/strong><\/li>\n
  • parameters<\/strong> – A lambda function can have zero<\/strong>, one<\/strong> or many parameters<\/strong>. You just need to specify comma-separated parameters<\/strong> after the lambda keyword.<\/li>\n
  • expression<\/strong> – This is the body<\/strong> of the function<\/strong>. This is where you specify the operation performed<\/strong> by the function<\/strong>. A lambda function can have only one expression<\/strong>.<\/li>\n<\/ul>\n

    Python Lambda function Example<\/strong><\/p>\n

    a. Lambda function with one parameter:<\/strong><\/p>\n

    >>> lambda x: x**2<\/pre>\n
    b. Lambda function with two parameters:<\/strong><\/p>\n
    >>> lambda x, y: 2(x + y)<\/pre>\n
    How to call a Lambda Expression in Python?<\/h3>\n
    A lambda function always returns<\/strong> a function object<\/strong>. So you can either call<\/strong> the lambda function directly<\/strong>:<\/p>\n
    >>> (lambda x: x ** 2)(10)<\/pre>\n
    Output<\/strong><\/p>\n
    100
    \n>>><\/div>\n
    or you can assign<\/strong> it a name<\/strong> and then you can call it<\/strong> like a traditional function call<\/strong>:<\/p>\n
    >>> square = lambda x: x ** 2\n>>> square(10)<\/pre>\n
    Output<\/strong><\/p>\n
    100
    \n>>><\/div>\n
    Lambda functions vs Traditional functions<\/h3>\n
    Let\u2019s look at the difference with the help of an example.<\/p>\n
    # traditional function to return the square of a number<\/strong><\/p>\n
    def square(x):\nreturn x ** 2<\/pre>\n
    # lambda function to calculate the square of a number<\/strong><\/p>\n
    square_lambda = lambda x: x ** 2\n\nprint(square(10))\nprint(square_lambda(10))\n<\/pre>\n
    All we\u2019ve done here is that we\u2019ve cleaned up some unnecessary syntax<\/strong> and changed some components<\/strong>. We use def<\/strong> to define a traditional function<\/strong>, whereas we use the lambda keyword<\/strong> to create a lambda<\/strong> function<\/strong>.<\/p>\n
    Also, in an anonymous function<\/strong>, we omit the return<\/strong> keyword<\/strong>, thereby further reducing the number of lines<\/strong>.<\/p>\n
    Other than these minor changes, let\u2019s compare the two types<\/strong> of functions at a greater depth.<\/p>\n\n\n\n\n\n\n\n\n
    Traditional Functions<\/b><\/td>\nLambda Functions<\/b><\/td>\n<\/tr>\n
    They can have multiple expressions\/ statements in their body.<\/span><\/td>\nThey can have just a single expression in their body.<\/span><\/td>\n<\/tr>\n
    These can have default values for their parameters.<\/span><\/td>\nLambda parameters can\u2019t have default values.<\/span><\/td>\n<\/tr>\n
    Normal function can return an object of any type.<\/span><\/td>\nLambda function always returns a function object.<\/span><\/td>\n<\/tr>\n
    It takes more time for execution as compared to lambda functions.<\/span><\/td>\nThese take relatively less time.<\/span><\/td>\n<\/tr>\n
    Require more lines of code.<\/span><\/td>\nIt requires a maximum of two lines of code to define and call a lambda function.<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
    How to use lambda Expression in your program?<\/h3>\n
    One of the superpowers of lambda functions is that we can use<\/strong> them inside any normal function in Python<\/strong>. Thanks to the simplicity<\/strong> of lambda functions!<\/p>\n
    This comes handy while working with high-order functions<\/strong>, i.e., the functions<\/strong> that take another function<\/strong> as an argument<\/strong>.<\/p>\n
    Let\u2019s have a look at two such functions – filter() and map().<\/strong><\/p>\n
    Using lambda expression with filter()<\/h3>\n
    The filter() function<\/strong> takes a function<\/strong> as its first argument<\/strong>. The second argument<\/strong> is an iterable<\/strong>, like, a list<\/strong>.<\/p>\n
    The filter() function then applies the argument function<\/strong> to every element<\/strong> of the iterable<\/strong>. It then returns<\/strong> a new iterable<\/strong> that contains all the elements<\/strong> for which the function<\/strong> evaluates to True<\/strong>.<\/p>\n
    Basically filter() filters out<\/strong> an iterable<\/strong> based on a function<\/strong>. It\u2019s like adding an if condition<\/strong> to the iterable<\/strong>.<\/p>\n
    This is where we can make use of lambda functions<\/strong>.<\/p>\n
    >>> numbers = [10, 45, 23, 56, 6, 34, 78, 90, 3]\n>>> filtered_list = list(filter(lambda x: x > 50, numbers))\n>>> print(filtered_list)<\/pre>\n
    Ouput<\/strong><\/p>\n
    [56, 78, 90]
    \n>>><\/div>\n
    Here the filtered_list<\/strong> contains all elements<\/strong> from the numbers list<\/strong> which are greater<\/strong> than 50<\/strong>.<\/p>\n
    Using Python lambda expression with map()<\/h3>\n
    Similar to filter()<\/strong>, the map()<\/strong> function takes a function as its first argument<\/strong>. And, the second argument<\/strong> is an iterable<\/strong>, like, a list<\/strong> or a tuple<\/strong>.<\/p>\n
    The map()<\/strong> function calls<\/strong> the argument<\/strong> function on every element<\/strong> of the iterable<\/strong>. It then returns<\/strong> a new iterable<\/strong> that contains <\/strong>the elements<\/strong> returned<\/strong> by that function<\/strong> for each element<\/strong> of the original iterable<\/strong>.<\/p>\n
    We can use lambda functions<\/strong> here as well.<\/p>\n
    >>> numbers = [10, 45, 23, 56, 6, 34, 78, 90, 3]\n>>> new_numbers = list(map(lambda x: x + 2, numbers))\n>>> print(new_numbers)<\/pre>\n
    Ouput<\/strong><\/p>\n
    [12, 47, 25, 58, 8, 36, 80, 92, 5]
    \n>>><\/div>\n
    The list new_numbers<\/strong> contains the elements<\/strong> of numbers added<\/strong> by 2<\/strong>.<\/p>\n
    Summary<\/h3>\n
    This article comes to an end now. Hope you\u2019ve got a better understanding<\/strong> of lambda functions<\/strong> through our article.<\/p>\n
    Lambda functions come in handy when you want to write quick \u201cuse-and-throw\u201d<\/strong> functions. If you find yourself writing a simple function<\/strong> which you\u2019re gonna use just once, think lambda! With Python, we have so many different features<\/strong> and concepts<\/strong> at our disposal<\/strong>.<\/p>\n
    It\u2019s on us to understand them and use them to their full potential<\/strong>.<\/p>\n","protected":false},"excerpt":{"rendered":"
    Python\u2019s Lambda expression are quite controversial in the programming circles. Some find it elegant and useful, while others freak out with the name of it. By the end of this article, you will be...<\/p>\n","protected":false},"author":1,"featured_media":79044,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1053],"tags":[2821,2822,2823,2824,2825],"class_list":["post-79043","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-python","tag-lambda-function","tag-lambda-function-python","tag-lammbda-expression","tag-python-lambda-expression","tag-python-lambda-function"],"yoast_head":"\nLambda Expression in Python - TechVidvan<\/title>\n<meta name=\"description\" content=\"What is Lambda Function in Python, its syntax and example, how to call python lambda expression, lambda vs traditional functions,filter() & map() for lambda\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/techvidvan.com\/tutorials\/lambda-expression-in-python\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Lambda Expression in Python - 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