Python itertools.tee() Function

The Pythonitertools.tee() function is used to create multiple independent iterators from a single iterable. These iterators share the same data but can be iterated over separately.

This function is useful when an iterable needs to be consumed multiple times in different parts of a program without reconstructing it.

Syntax

Following is the syntax of the Python itertools.tee() function −

itertools.tee(iterable, n=2)

Parameters

This function accepts the following parameters −

• iterable: The input iterable that needs to be duplicated.
• n (optional): The number of independent iterators to create (default is 2).

Return Value

This function returns a tuple containingn independent iterators.

Example 1

Following is an example of the Python itertools.tee() function. Here, we create two iterators from a single iterable and iterate over them independently −

import itertoolsnumbers = [1, 2, 3, 4, 5]iter1, iter2 = itertools.tee(numbers)print("Iterator 1:")for num in iter1:   print(num)print("Iterator 2:")for num in iter2:   print(num)

Following is the output of the above code −

Iterator 1:12345Iterator 2:12345

Example 2

Here, we create three independent iterators and use them separately to process data −

import itertoolsdata = ["apple", "banana", "cherry"]iter1, iter2, iter3 = itertools.tee(data, 3)print("First iterator:", list(iter1))print("Second iterator:", list(iter2))print("Third iterator:", list(iter3))

Output of the above code is as follows −

First iterator: ['apple', 'banana', 'cherry']Second iterator: ['apple', 'banana', 'cherry']Third iterator: ['apple', 'banana', 'cherry']

Example 3

Now, we use itertools.tee() function with a filtering operation. We first split an iterator and apply different processing techniques on each copy −

import itertoolsnumbers = [10, 20, 30, 40, 50]iter1, iter2 = itertools.tee(numbers)# Use one iterator to find sumsum_values = sum(iter1)print("Sum of numbers:", sum_values)# Use second iterator to find maximum valuemax_value = max(iter2)print("Maximum value:", max_value)

The result obtained is as shown below −

Sum of numbers: 150Maximum value: 50

Example 4

When using itertools.tee() function, consuming one iterator completely affects the others. To avoid unexpected behavior, convert iterators to lists if necessary −

import itertoolsdata = [1, 2, 3, 4]iter1, iter2 = itertools.tee(data)print("Using first iterator:")for num in iter1:   print(num)print("Using second iterator:")print(list(iter2))

The result produced is as follows −

Using first iterator:1234Using second iterator:[1, 2, 3, 4]