{"id":79294,"date":"2020-07-06T11:30:39","date_gmt":"2020-07-06T06:00:39","guid":{"rendered":"https:\/\/techvidvan.com\/tutorials\/?p=79294"},"modified":"2020-07-06T11:30:39","modified_gmt":"2020-07-06T06:00:39","slug":"closures-in-python","status":"publish","type":"post","link":"https:\/\/techvidvan.com\/tutorials\/closures-in-python\/","title":{"rendered":"Closures in Python with Examples"},"content":{"rendered":"

If you have been into programming for a while, chances are you might\u2019ve heard the word \u2018Closure\u2019<\/strong> in JavaScript<\/strong>. Turns out, closures<\/strong> are not limited<\/strong> to JavaScript<\/strong>.<\/p>\n

Python<\/strong> offers support<\/strong> for closures<\/strong> too. In this article, we\u2019ll learn what closures in Python are, how to define<\/strong> them and lastly, when<\/strong>, and why you should use them<\/strong>.<\/p>\n

What are Closures in Python?<\/h3>\n

Like nested loops<\/strong>, we can also nest functions<\/strong>. That said, Python gives us the power<\/strong> to define functions<\/strong> within functions<\/strong>.<\/p>\n

Python Closures <\/strong>are these inner functions <\/strong>that are enclosed within <\/strong>the outer function<\/strong>. Closures can access variables<\/strong> present in the outer function scope<\/strong>. It can access<\/strong> these variables<\/strong> even after the outer function<\/strong> has completed<\/strong> its execution<\/strong>.<\/p>\n

To get a better understanding of closures, let\u2019s first see how scope works in nested functions<\/strong>.<\/p>\n

Scope of Variables in Nested Functions<\/h3>\n

In Python nested functions, the enclosed function<\/strong> can access variables<\/strong> of the enclosing scope<\/strong>.<\/p>\n

Let\u2019s understand this better with an example –<\/p>\n

def outer(name):\n    # this is the enclosing function\n\n    def inner():\n        # this is the enclosed function\n\n        # the inner function accessing the outer function's variable 'name'\n        print(name)\n\n    inner()\n\n# call the enclosing function\nouter('TechVidvan')\n<\/pre>\n
Output<\/strong><\/p>\n
TechVidvan<\/p>\n
Let\u2019s break this code down.<\/p>\n
When the outer function<\/strong> gets called<\/strong>, the variable \u2018name\u2019<\/strong> gets the value \u2018TechVidvan\u2019<\/strong>. The inner function<\/strong> can access<\/strong> the value<\/strong> of this variable<\/strong>. When the inner function<\/strong> gets called<\/strong>, \u2018Techvidvan\u2019 gets printed<\/strong>. This is how scope<\/strong> works in nested functions<\/strong>.<\/p>\n
The bottom line is (and it\u2019s worth repeating) – \u201cEnclosed functions can access the variables of enclosing functions.\u201d<\/strong><\/p>\n
Keeping this in mind, let\u2019s move on to Python closures<\/strong>.<\/p>\n
Python Closures<\/h3>\n
In the example above, we have called<\/strong> the inner function inside<\/strong> the outer function<\/strong>. The inner function <\/strong>becomes a closure <\/strong>when we return <\/strong>the inner function instead of calling it.<\/strong><\/p>\n
So we have a closure in Python if-<\/p>\n
    \n
  • We have a nested function, i.e. function within a function<\/strong><\/li>\n
  • The nested function refers to a variable<\/strong> of the outer function<\/strong><\/li>\n
  • The enclosing function returns<\/strong> the enclosed function<\/strong><\/li>\n<\/ul>\n
    For Example<\/strong><\/p>\n
    def outer(name):\n    # this is the enclosing function\n\n    def inner():\n        # this is the enclosed function\n        # the inner function accessing the outer function's variable 'name'\n        print(name)\n\n    return inner\n\n# call the enclosing function\nmyFunction = outer('TechVidvan')\nmyFunction()\n<\/pre>\n
    Output<\/strong><\/p>\n
    \u2018TechVidvan\u2019<\/p>\n
    Here, the call<\/strong> to outer function<\/strong> returns<\/strong> the inner function<\/strong>. This then gets assigned to \u2018myFunction\u2019<\/strong>. Now when we call myFunction<\/strong>, it prints<\/strong> \u2018TechVidvan\u2019<\/strong> (which was earlier given as an argument<\/strong> to outer<\/strong>).<\/p>\n
    Do you see what just happened here? Even after \u2018outer\u2019<\/strong> finishes<\/strong> its execution<\/strong> and all its variables go out of scope<\/strong>, the value passed<\/strong> to its argument<\/strong> is still remembered<\/strong>.<\/p>\n
    This is the beauty of closures! We can access<\/strong> the values<\/strong> of a function<\/strong> that no longer exists<\/strong>. You might be thinking that closure<\/strong> and all seems fine, but why on Earth will I ever use it?<\/p>\n
    Say no more, pal!<\/p>\n
    When and Why do you need to use Closures in Python?<\/h3>\n
    You can use closures –<\/p>\n
      \n
    • To replace the unnecessary use of class:<\/strong> Suppose you have a class that contains just one method besides the __init__ method<\/strong>. In such cases, it is often more elegant to use a closure<\/strong> instead of a class<\/strong>.<\/li>\n
    • To avoid the use of the global scope:<\/strong> If you have global variables which only one function<\/strong> in your program will use, think closure. Define the variables in the outer function<\/strong> and use them in the inner function<\/strong>.<\/li>\n
    • To implement data hiding:<\/strong> The only way to access the enclosed function is by calling the enclosing function<\/strong>. There is no way to access the inner function directly<\/strong>.<\/li>\n
    • To remember a function environment even after it completes its execution:<\/strong> You can then access<\/strong> the variables<\/strong> of this environment later in your program.<\/li>\n<\/ul>\n
      Wrapping Up!<\/h3>\n
      Closures are just functions<\/strong>, but with an extra<\/strong> environment of variables<\/strong>. They might seem quite confusing<\/strong> at first. It will take you a while to understand<\/strong> them, let alone use them in your program. But once you get a hang of it, you\u2019ll realize how powerful<\/strong> they are.<\/p>\n","protected":false},"excerpt":{"rendered":"
      If you have been into programming for a while, chances are you might\u2019ve heard the word \u2018Closure\u2019 in JavaScript. Turns out, closures are not limited to JavaScript. Python offers support for closures too. In...<\/p>\n","protected":false},"author":1,"featured_media":79404,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1053],"tags":[2989,2990,2991],"class_list":["post-79294","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-python","tag-advantages-of-python-closures","tag-closures-in-python","tag-python-closures"],"yoast_head":"\nClosures in Python with Examples - TechVidvan<\/title>\n<meta name=\"description\" content=\"Learn what are closures in python, why and when to use them, Scope of Variables in Nested Functions and Python closure example for better understanding.\" \/>\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\/closures-in-python\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Closures in Python with Examples - 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