{"id":4345,"date":"2021-06-05T19:25:52","date_gmt":"2021-06-05T13:55:52","guid":{"rendered":"https:\/\/blog.guvi.in\/?p=4345"},"modified":"2026-02-04T12:45:30","modified_gmt":"2026-02-04T07:15:30","slug":"understanding-the-yield-keyword-in-python","status":"publish","type":"post","link":"https:\/\/www.guvi.in\/blog\/understanding-the-yield-keyword-in-python\/","title":{"rendered":"What Does the yield Keyword In Python Do?"},"content":{"rendered":"\n

If you are a beginner and have recently started learning to program then you must have come across the \u2018<\/span>yield<\/b>\u2019 keyword in Python. <\/span><\/p>\n\n\n\n

There is a big possibility that you might feel confused about what it is! On the other hand, you might already know about it, then the other question that could arise in your mind is why use the \u2018<\/span>yield<\/b>\u2019 keyword in python when we can use the \u2018<\/span>return<\/b>\u2019 keyword. <\/span><\/p>\n\n\n\n

This curiosity of yours has brought you to the right place. Because in this article we will be reading about the \u2018yield\u2019 keyword in Python. Thereby we will try to understand the scenarios when the usage of the \u2018yield\u2019 keyword can be beneficial to us as a programmer. We will eventually understand why we need to use the \u2018yield\u2019 keyword instead of using the \u2018return\u2019 keyword. Apart from this, we will also be introducing you to the concept of <\/span>generators<\/b> in Python. <\/span><\/p>\n\n\n\n

One of the biggest dilemmas a beginner will ever come across in Python language is when to use the \u2018return\u2019 keyword and when to use the \u2018yield\u2019 keyword. Provided you know that both of these are used to return some value out of a function. <\/span><\/p>\n\n\n\n

The above statement can be more accurately stated as:<\/span><\/p>\n\n\n\n

the \u2018yield\u2019 keyword in python is used to make generator functions and usually returns generator objects.<\/i><\/b><\/p>\n\n\n\n

Now, you must be wondering what exactly a <\/span>generator<\/b> function is. We\u2019ll discuss it in the upcoming section.<\/span><\/p>\n\n\n\n

Generators in Python<\/b><\/em><\/h2>\n\n\n\n

A generator function<\/a> is just like a normal function that is used to return some values but instead of using the usual <\/span>return<\/b> keyword, we make use of the <\/span>yield<\/b> keyword to return the value in the function.  The values returned are generated spontaneously. If the body of a user-defined function contains the <\/span>yield<\/b> keyword, that function automatically acts as a generator function. <\/span><\/p>\n\n\n\n

As soon as the \u2018yield\u2019 keyword is executed inside the function, it yields back a generator object. The generator object is iterable in nature. Also, it could be iterated only once as the items are produced randomly by the generator. These values are not stored fully in memory. Thereafter, the control of the function returns to the caller. <\/span><\/p>\n\n\n\n

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We can print the items produced by the generator by either calling the <\/span>next()<\/b><\/a> method again and again or by iterating over the generator object using them <\/span>for<\/b> a loop. Inside the generator function, the yield keyword helps to maintain the current state of the local variable in the function. Here, the function when called again starts executing from the last yield statement. It is beneficial as it doesn\u2019t use much memory and also saves a lot of computational time.<\/span><\/p>\n\n\n\n

Syntax of a generator function<\/b><\/em><\/h2>\n\n\n\n
\"syntax<\/figure>\n\n\n\n

Let\u2019s work on an example to understand the functioning of generator function and yield keyword more clearly. Have a look at the below-given code snippet:<\/span><\/p>\n\n\n\n

\"generator<\/figure>\n\n\n\n

In the above-written code snippet, we have written a generator function that generates an odd number from a given list of numbers. We can observe the function consists of a yield statement that yields the value \u2018i\u2019. <\/span><\/p>\n\n\n\n

When we make a call to the generator function, it returns us a generator object that can be verified by printing the value of the \u2018gen\u2019 variable. As the generator object is iterable we can obtain its value by iterating over it. And for that, we are using the <\/span>next()<\/b> method available in Python that is used to return the next value in an iterator. <\/span><\/p>\n\n\n\n

Every time we call the next() method over the generator object, it yields a single value. After that, the control goes back to the calling statement. Also, we need to note the point that the value of the local variable \u2018i\u2019 does not get reset as the control flows back to the calling function. Here, the current state of the variable remains intact. And the next item in the generator gets printed. <\/span><\/p>\n\n\n\n

As items are being generated on the fly and are not stored in memory, the memory is saved. Also, computation becomes faster because the loop doesn\u2019t need to restart from the beginning again and again. The output of the above-written code is given below.<\/span><\/p>\n\n\n\n

Output:<\/b><\/h3>\n\n\n\n
\"output<\/figure>\n\n\n\n

Reading the generated values using for loop<\/b><\/em><\/h2>\n\n\n\n

In the above code, we have used the <\/span>next()<\/b> method to read generated values again and again. In this section, we will be using the <\/span>for<\/b> loop to read the values generated by the generator. Let\u2019s rewrite the previous code after making some changes:<\/span><\/p>\n\n\n\n

\"generated<\/figure>\n\n\n\n

Upon saving and executing the code the output will be generated as:<\/span><\/p>\n\n\n\n

\"code<\/figure>\n\n\n\n

We can also notice from the output that when we retry to print the items stored inside the generator object in the form of a list, it only prints an empty list.<\/span><\/p>\n\n\n\n

This verifies the fact that the items are generated spontaneously and can be iterated\/ read-only once. The items inside the generator object get removed from the memory afterward and are not placed permanently. To read\/view those items once again, we have to again call the generator function.<\/span><\/p>\n\n\n\n

Scenarios where usage of yield keyword in Python is beneficial to a programmer:<\/b><\/em><\/h2>\n\n\n\n

Given below are some pointers which discuss the usage of the \u2018yield\u2019 keyword in Python:<\/span><\/p>\n\n\n\n