98. functools.reduce

Here are 10 Python code snippets demonstrating how to use functools.reduce to apply a binary function cumulatively to items of an iterable:

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1. Summing 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: 15

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2. Finding the Product of Numbers

from functools import reduce

numbers = [1, 2, 3, 4, 5]
result = reduce(lambda x, y: x * y, numbers)
print(result)  # Output: 120

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3. Finding the Maximum Value

from functools import reduce

numbers = [5, 3, 8, 2, 7]
result = reduce(lambda x, y: x if x > y else y, numbers)
print(result)  # Output: 8

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4. Flattening a Nested List

from functools import reduce

nested_list = [[1, 2], [3, 4], [5, 6]]
result = reduce(lambda x, y: x + y, nested_list)
print(result)  # Output: [1, 2, 3, 4, 5, 6]

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5. Concatenating Strings

from functools import reduce

words = ["Python", "is", "awesome"]
result = reduce(lambda x, y: x + " " + y, words)
print(result)  # Output: Python is awesome

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6. Calculating Factorial

from functools import reduce

n = 5
factorial = reduce(lambda x, y: x * y, range(1, n + 1))
print(factorial)  # Output: 120

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7. Counting Character Frequencies

from functools import reduce
from collections import Counter

text = "hello world"
result = reduce(lambda acc, char: acc.update({char: acc.get(char, 0) + 1}) or acc, text, Counter())
print(result)  # Output: Counter({'l': 3, 'o': 2, 'h': 1, 'e': 1, ' ': 1, 'w': 1, 'r': 1, 'd': 1})

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8. Finding the Greatest Common Divisor (GCD)

from functools import reduce
from math import gcd

numbers = [48, 72, 120]
result = reduce(gcd, numbers)
print(result)  # Output: 24

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9. Merging Dictionaries

from functools import reduce

dicts = [{"a": 1}, {"b": 2}, {"c": 3}]
result = reduce(lambda x, y: {**x, **y}, dicts)
print(result)  # Output: {'a': 1, 'b': 2, 'c': 3}

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10. Calculating Dot Product

from functools import reduce

vector1 = [1, 2, 3]
vector2 = [4, 5, 6]
result = reduce(lambda acc, xy: acc + xy[0] * xy[1], zip(vector1, vector2), 0)
print(result)  # Output: 32

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These examples show the versatility of functools.reduce, which can be used in a wide range of scenarios, from simple numerical operations to more complex tasks like dictionary merging or working with nested structures.