How Can I Efficiently Calculate the Cumulative Sum of a List in Python?

Cumulative Sum in Python

Question:

How can we find the cumulative sum of numbers in a list, like [4, 4 6, 4 6 12]?

Introduction:

Calculating the cumulative sum involves repeatedly adding the next element to the running sum. While this can be achieved with a straightforward loop, there are more efficient approaches using NumPy or custom Python generators.

NumPy Method:

NumPy's cumsum function provides an efficient solution:

import numpy as np

time_interval = [4, 6, 12]
np.cumsum(time_interval)
# Output: [4, 10, 22]

This approach is highly optimized and recommended for numerical operations on large arrays.

Python Generator:

For concise and memory-efficient solutions in pure Python, consider using a generator:

def accumu(iterable):
    yield next(iterable)
    for item in iterable:
        yield item + sum(accumu(iterable))

Using this generator:

list(accumu(time_interval))
# Output: [4, 10, 22]

This generator lazily accumulates elements, making it suitable for iterating over large sequences or when memory is a concern.

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