Generators in Python | Methods & Expression

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Python generators allow us to create iterators in a convenient and efficient way. Generators in Python provide a simple way to define iterable objects, which can be used to generate a sequence of values on the fly without storing them in memory all at once.

This makes generators particularly useful when dealing with large datasets or infinite sequences.

How to create a generator in Python?

To create a generator, we use a special kind of function called a generator function.

A generator function is defined like a regular function, but it uses the yield keyword instead of return to produce a series of values.

Example of a number generator function in Python

def number_generator(n):
    i = 0
    while i < n:
        yield i
        i += 1

Here, the number_generator function is defined with a parameter n, which specifies the upper limit of the sequence. Inside the function, the yield statement is used to produce each number in the sequence.

When the generator function is called, it returns a generator object, which can be iterated over using a for loop or by using the next() function.

my_generator = number_generator(5)

for num in my_generator:



Generators are particularly useful when dealing with large datasets that don’t fit entirely into memory.

Since generators produce values on-demand, they only hold one value at a time, saving memory. This is known as lazy evaluation.

Generator Expression in Python

In addition to generator functions, Python also supports generator expressions, which are a concise way to create generators. Generator expressions have a similar syntax to list comprehensions but are enclosed in parentheses instead of square brackets.

Example of Generator Expression in Python

squares = (x**2 for x in range(5))

for num in squares:



Here, the generator expression (x**2 for x in range(5)) generates a sequence of squares of numbers from 0 to 4. The generator expression consists of an expression x**2 followed by a loop for x in range(5), which specifies the values to be processed.

We can also combine multiple generator expressions using various operations such as zip(), filter(), or map().

Here’s an example that combines two generator expressions using zip():

numbers = range(5)
squares = (x**2 for x in numbers)
cubes = (x**3 for x in numbers)

for num, square, cube in zip(numbers, squares, cubes):
    print(num, square, cube)


0 0 0
1 1 1
2 4 8
3 9 27
4 16 64

Here, the zip() function combines the three generator expressions numbers, squares, and cubes to iterate over them simultaneously.

Use of Python Generators

  • Generating Large Datasets: Generators are ideal for generating large datasets that don’t fit entirely into memory. Instead of storing all the data in memory at once, generators produce values on demand, allowing you to process the data iteratively. This saves memory and enables the efficient handling of large datasets.
  • Stream Processing: Generators are well-suited for stream processing tasks, where data arrives continuously over time. We can use a generator to process incoming data as it becomes available, without waiting for the entire stream to be loaded. This is especially useful in scenarios like reading data from files, network streams, or databases.
  • Infinite Sequences: Generators can be used to create infinite sequences of values. For example, generating prime numbers, Fibonacci series, or an infinite stream of random numbers. By using lazy evaluation, generators allow us to work with sequences that are theoretically infinite without requiring excessive memory.
  • Memory-Efficient Iteration: When iterating over a collection of elements, generators provide memory-efficient iteration. Instead of loading all the elements into memory at once, generators produce one element at a time, reducing memory consumption. This is beneficial when dealing with large collections or when the number of elements is not known in advance.
  • Data Pipelines and Processing Chains: Generators can be combined in pipelines or processing chains to perform complex data transformations. Each generator in the chain processes the data and passes it to the next generator, allowing us to break down complex tasks into smaller, reusable components. This promotes modularity and improves code organization.
  • Asynchronous Programming: Generators can be used as a foundation for implementing asynchronous programming patterns. By utilizing the yield statement with appropriate libraries like asyncio, we can create asynchronous generators that produce values as they become available, allowing us to write efficient and responsive asynchronous code.
  • Resource Management: Generators can assist in managing resources that need proper cleanup, such as file handles or network connections. By using generators with the with statement, we can ensure that resources are properly closed or cleaned up after they are no longer needed, even if exceptions occur.

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