Python Tutorial



Python Tutorial

Yield in Python


As we journey through Python's extensive toolkit, we encounter the yield keyword—a tool of paramount importance for professionals seeking efficiency and power in their coding repertoire. This tutorial is designed for those who, while familiar with Python's basics, aim to dive deeper and harness the true potential of yield in Python.


In this tutorial, we will delve into the mechanics of yield in Python. Through detailed explanations and real-world examples, you'll grasp the concept, discern its advantages, understand its differences from the return statement, and master its use in advanced Python coding.

What is yield in Python?  

When it comes to Python programming, a few tools stand out for their profound impact on code efficiency and versatility. Among them, the yield keyword emerges as a cornerstone when discussing generators. To put it into perspective, when one browses through the Python yield documentation, it is evident that this keyword plays a pivotal role in crafting more responsive and memory-efficient applications.

Python's yield can be envisioned as a unique tool in a coder's arsenal. Think of a traditional function as a machine that produces a product once the entire operation is complete. The yield keyword, on the other hand, allows a function to produce intermediate products, turning the machine into a more dynamic entity. Such a function doesn't just conclude after a single run; it pauses, retains its operational state, and can resume on command. This transformation from a traditional function to this dynamic entity is termed as a "generator".

How Does yield Work?

Delving deeper into its mechanics, when a Python function containing the yield keyword is invoked, it promptly hands back a generator object. This object remains dormant initially. However, once we call the __next__() method on this generator, the function awakens and commences its execution. It continues to run until it stumbles upon the yield keyword, upon which it takes a pause, memorizing its current state, and provides the yielded value. It's akin to a bookmark in a book, enabling readers to resume from where they left off. Thus, in future interactions, by invoking __next__(), the function picks up the pace from its last bookmark, or where it was previously paused.

In Python, especially when one considers scenarios like handling vast datasets or streaming data, the efficiency introduced by yield becomes undeniably essential. It fosters an environment where data is generated on demand, rather than consuming substantial memory by storing colossal datasets. For professionals striving to achieve optimal performance, understanding and adeptly using the yield keyword can be a game-changer.

Example of Generator Functions and yeild in Python

def number_generator(n):
    for i in range(n):
        yield i

# Using the generator function
gen = number_generator(5)
for num in gen:

In this example, number_generator is a generator function that yields numbers from 0 to n-1. When you iterate over the generator, it yields values one at a time.

Generating an Infinite Sequence in Python

def infinite_sequence():
    num = 0
    while True:
        yield num
        num += 1

# Using the infinite sequence generator
gen = infinite_sequence()
for i in range(5):

Here, infinite_sequence is a generator function that yields an infinite sequence of numbers. You can use next() to retrieve values from the generator, and it will keep generating values indefinitely.

Example of Using yield With a List

def list_generator(lst):
    for item in lst:
        yield item

# Using the list generator
my_list = [1, 2, 3, 4, 5]
gen = list_generator(my_list)
for item in gen:

In this case, list_generator is a generator function that yields items from a given list one by one.

Example of Using of yield Keyword as Boolean

def boolean_generator():
    yield True
    yield False

# Using the boolean generator
gen = boolean_generator()
for value in gen:

Here, boolean_generator is a generator function that yields True and then False. You can use this to iterate over boolean values.

Difference between return and yield Python 

In the Python programming language, understanding the nuances between various keywords can drastically influence the efficiency and clarity of code. Two such vital keywords, yield and return, often lead to confusion among developers due to their similar nature of handling outputs. However, their operational differences set them apart in various scenarios.

1. Purpose and Functionality: At its core, the return statement marks the termination of a function's execution, immediately handing back a specified value to the caller. Once return is executed, the function’s state and local variables are lost. On the other hand, yield is slightly more complex. Instead of concluding a function, it momentarily halts its execution, preserving its current state. This paused state can then be continued, in subsequent calls, ensuring the function retains its last known state and variables.

2. Memory Consumption: A clear divergence between the two is evident when we analyze memory usage. Functions that utilize the return keyword allocate memory for the entirety of their output. This can be problematic when handling large datasets, as the entire dataset must reside in memory. Conversely, yield showcases its prowess in memory efficiency. By generating and providing values on-the-fly, it ensures minimal memory consumption, particularly beneficial when working with extensive data streams.

3. Execution Flow: With return, once the function has completed its execution and delivered its result, any subsequent calls initiate the function from the beginning. In contrast, yield maintains a continuous flow. After yielding a value, the function can be resumed right where it paused, ensuring a seamless data generation process.

4. Use Cases: Traditional functions employing the return keyword are perfect for scenarios where a complete result set is required instantaneously. It's straightforward and ensures immediate output. However, yield emerges as the victor in situations where data is to be processed or consumed sequentially or piece-by-piece. This is particularly handy in applications like data streaming or lazy evaluation.

5. Multiplicity of Outputs: Functions utilizing return provide a single output value, once the execution is completed. In contrast, those with yield have the potential to yield multiple outputs over time, every time the function encounters the yield statement.

The awareness of these distinctions is pivotal for developers looking to optimize their Python applications. Both return and yield have their unique advantages and best-fit scenarios; thus, judiciously choosing between them can make a considerable difference in performance and resource utilization.

Advantages and Disadvantages of yield in Python 

The Python programming landscape is adorned with powerful constructs and features. Among them, the yield keyword stands out as a particularly unique tool. It's imperative for developers to grasp both the benefits and challenges associated with yield to employ it judiciously in their Python applications.


  1. Efficient Memory Usage: One of the primary strengths of the yield keyword lies in its memory efficiency. Traditional functions, when dealing with extensive datasets, might necessitate the allocation of vast amounts of memory to hold their results. With yield, such concerns are alleviated. Instead of storing the entire set of results simultaneously, the function generates and yields each result individually, significantly reducing memory consumption.

  2. Dynamic Data Generation: Generators, powered by the yield keyword, shine in scenarios requiring dynamic data generation. They are capable of generating and yielding data based on evolving conditions or inputs, offering a level of flexibility that's challenging to achieve with standard functions.

  3. Better Control Flow: The beauty of yield is that it doesn't merely end a function's execution. Instead, it temporarily halts it, preserving its current state. This pause-and-resume mechanism bestows developers with unparalleled control over the function's execution flow, making it easier to produce data in stages or respond to external conditions.


  1. Learning Curve: Integrating yield into one's coding arsenal demands a paradigm shift. Developers accustomed to standard function constructs might find generators, and the accompanying yield mechanism, a bit challenging initially.

  2. Debugging Challenges: The very feature that makes yield so versatile, its ability to pause and resume, can occasionally be its Achilles' heel. Debugging a generator function can become intricate due to its non-linear execution flow.

  3. Specific Use Cases: While yield offers a plethora of advantages, it's not a one-size-fits-all solution. There exist scenarios where a traditional function or another approach might be more apt.

While yield is undeniably powerful, its effective deployment requires a discerning understanding of its strengths and limitations. Balancing its advantages against its challenges ensures optimized, efficient, and streamlined Python code.


The journey into understanding yield in Python offers insights into crafting more efficient and controlled Python applications. While the yield keyword brings undeniable advantages, it's crucial to employ it thoughtfully, aligning with the specific requirements of your project. For those yearning to delve deeper and refine their expertise, upGrad presents a plethora of courses tailored to upskill the modern Python professional.


1. Is there a clear winner in the debate of yield vs return in Python?

While both have their applications, the choice depends on the specific requirements, with yield excelling in memory efficiency and return being straightforward.

2. What role does the Python yield generator play?

A Python yield generator provides a way to produce a series of values over time, making it memory-efficient and dynamic.

3. Can I refer to the official yield Python documentation for more in-depth knowledge?

Absolutely. The Python official documentation provides a thorough exploration of yield and its applications.

4. Is it recommended to use Python yield and return in same function?

While feasible, it can lead to confusion. It's crucial to ensure clarity in the function's purpose.

5. How do I utilize the Python yield send method effectively?

The send method allows values to be passed back into a generator function, offering dynamic input during its execution.

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