如何从python列表中删除特定元素？

Question

I want to remove an A element using a B array of IDs, given the specific scalar ID 'C'

In matlab I can do this:

A(B == C) = []

This is an example of my code:

 boxes = [[1,2,20,20],[4,8,20,20],[8,10,40,40]]
 boxIDs = [1,2,3]


IDx = 2

I want to delete the second box completely out of the list.

How can I do this in python? I have numpy.

Answer 1

without import numpy you can pop out the element. try:

boxes = [[1,2,20,20],[4,8,20,20],[8,10,40,40]]
IDx = 1
pop_element = boxes.pop(IDx)

the list boxes now is [[1, 2, 20, 20], [8, 10, 40, 40]] and pop_element is [4, 8, 20, 20]

PS: in python indexes start from 0 instead of 1 .

Answer 2

You could use numpy indexing for that. You could find more information in the docs . For your case:

import numpy as np
boxes = np.array([[1,2,20,20],[4,8,20,20],[8,10,40,40]])
boxIDs = np.array([1,2,3])

IDx = 2

In [98]: boxes[boxIDs != IDx, :]
Out[98]:
array([[ 1,  2, 20, 20],
       [ 8, 10, 40, 40]])

Answer 3

In plain-old-Python, I think you want to do this:

try:
    helpindex = boxIDs.index(IDx)
    del boxes[index], boxIDs[index]
except ValueError:
    # Already deleted
    pass

Note that if you are relying on boxIDs to be "parallel" with boxes , you have to make sure you keep them parallel by deleting from both.