Deleting matching items from a list-CodePudding

I have a list of values. I would like to remove values which cancel to each other ( and -). The values are randomly in the list, so I first added a new column in excel with the absolute values. I then sorted on the absolute values so the amounts which needs to be cancelled are below each other.

I was thinking to create a for loop and sum up the ifrst row with the second row, and when this sums to zero, delete both rows and start from the top again. Please refer to the picture of an example. I have marked yellow the items which should be deleted. As I only want to delete matching items, the total sum of the amount column should not change after the operation.

example

Currently I have something like this

for i in df["Amount in Entity Currency"]: if df["Amount in Entity Currency"][i] df["Amount in Entity Currency"][i 1] == 0: df.drop(df[df["Amount in Entity Currency"][i]]) df.drop(df[df["Amount in Entity Currency"][i 1]])

CodePudding user response：

try sth like this after you have sorted the list (as you already said):

for i,elem in enumerate(yourList):
    nextElem = yourList[i 1]
    if (elem   nextElem < 0.00000001): 
        yourList.remove(elem)
        yourList.remove(nextElem)

CodePudding user response：

I would base an answer off of several building blocks. First is creating two "iterable" sub-lists. One for positive numbers and the other negative numbers.

Then I would iterate over both of them using next() and as long as one of the two lists had values I would act on the current values as appropriate.

import random

full_data = [random.randint(0, 10) for _ in range(20)]   [-random.randint(0, 10) for _ in range(20)]

zeros = [i for i in full_data if i == 0]
positives = iter(sorted([i for i in full_data if i > 0]))
negatives = iter(sorted([i for i in full_data if i < 0], reverse=True))

## ------------------------------
## prime the list with zero or 1 0s where an odd number of 0s
## results in [0] as the evens cancel each other out.
## ------------------------------
result = [0] * (len(zeros) % 2)
## ------------------------------

pos = next(positives, None)
neg = next(negatives, None)
while pos is not None or neg is not None:
    if pos is None:
        # we ran out of positive numbers so add any remaining negatives
        result.extend([neg]   list(negatives))
        break

    if neg is None:
        # we ran out of negative numbers so add any remaining positives
        result.extend([pos]   list(positives))
        break

    if pos == -neg:
        # these results cancel each other
        pos = next(positives, None)
        neg = next(negatives, None)

    elif pos > -neg:
        # this positive is "larger" then this negative so add the negative
        result.append(neg)
        neg = next(negatives, None)

    else:
        # this positive is "smaller" than this negative so add the positive
        result.append(pos)
        pos = next(positives, None)

print(f"The original list has {len(full_data)} items and sums to: {sum(full_data)}")
print(f"The filtered list has {len(result)} items and sums to: {sum(result)}")