🚀 Day 98/150 – reduce() Function in Python

The reduce() function is used to repeatedly apply a function to the elements of an iterable until a single value is produced. Unlike map() and filter(), reduce() returns one final result instead of another iterable.

The reduce() function is available in Python's functools module.

Syntax:

from functools import reduce 

reduce(function, iterable)

In this post, we'll explore four common examples of using the reduce() function in Python.

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Method 1 – Using reduce() with a Normal Function

Find the sum of all numbers in a list.

from functools import reduce

def add(x, y):
    return x + y

numbers = [1, 2, 3, 4, 5]

result = reduce(add, numbers)

print(result)

Output

15

Explanation

• add() takes two numbers and returns their sum.

• reduce() repeatedly applies the function to the list.

• Calculation:

  (1 + 2) = 3
  
  
  (3 + 3) = 6
  
  
  (6 + 4) = 10
  
  
  (10 + 5) = 15

  • The final result is 15.

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Method 2 – Using reduce() with a Lambda Function

Find the product of all numbers in a list.

from functools import reduce

numbers = [1, 2, 3, 4, 5]

result = reduce(lambda x, y: x * y, numbers)

print(result)







Output

120

Explanation

• lambda x, y: x * y multiplies two numbers.

• reduce() applies the lambda function repeatedly.

• Calculation:

  
  (1 × 2) = 2
  
  
  (2 × 3) = 6
  
  
  (6 × 4) = 24
  
  
  (24 × 5) = 120

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Method 3 – Find the Maximum Value

Use reduce() to find the largest element in a list.

from functools import reduce

numbers = [12, 45, 7, 89, 23]

maximum = reduce(lambda x, y: x if x > y else y, numbers)

print(maximum)








Output

89

Explanation

• The lambda function compares two numbers.

• It returns the larger one each time.

• After all comparisons, the largest value remains.

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Method 4 – Taking User Input

Find the sum of numbers entered by the user.

from functools import reduce

numbers = list(map(int, input("Enter numbers separated by spaces: ").split()))

result = reduce(lambda x, y: x + y, numbers)

print("Sum:", result)













Sample Input

10 20 30 40

Output

Sum: 100

Explanation

• input() reads the numbers as a string.

• split() separates them into individual values.

• map(int, ...) converts each value to an integer.

• reduce() adds all the numbers and returns a single sum.

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Comparison of Methods

Method	Best For
Normal Function	Reusable reduction logic
Lambda Function	Short and simple operations
Finding Maximum	Comparing elements
User Input	Interactive programs

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🔥 Key Takeaways

• reduce() is available in the functools module.

• It applies a function repeatedly to reduce an iterable to a single value.

• reduce() works with both normal functions and lambda functions.

• It is commonly used for operations like sum, product, maximum, and minimum.

• Unlike map() and filter(), reduce() returns a single result instead of an iterable.

Stay tuned for Day 99 of the #150DaysOfPython series! 🚀