[FIXED] How to subtract a value from the first element of an array?

Issue

I want to subtract a number x from the first element of the array, and in case the first element in the array is smaller than x I want to subtract the remaining amount from the second element of the array and so on.

I have tried this:

import numpy as np

x = 25
y = np.array([22, 30, 45])
result = np.copy(y)

for i in range(len(y)):
    if y[i] < x:
        result[i] = y[i] - x
        x = x - y[i]
    else:
        result[i] = y[i] - x
        x = x - y[i]

I get this result:

array([-3, 27, 72])

But I want to have

array([0, 27, 45])

Solution

• In the if case, you should assign 0

• In the else case there must be a break to stop as all value to remove has been consumed

def sub_array(array, to_remove):
    result = np.copy(array)
    for i in range(len(array)):
        if array[i] < to_remove:
            result[i] = 0
            to_remove -= array[i]
        else:
            result[i] = array[i] - to_remove
            break
    return result

print(sub_array(np.array([10, 10, 10]), 39))  # [0  0  0]
print(sub_array(np.array([10, 10, 10]), 29))  # [0  0  1]
print(sub_array(np.array([10, 10, 10]), 19))  # [0  1 10]
print(sub_array(np.array([10, 10, 10]), 9))   # [1 10 10]

Answered By - azro