Subtracting arrays from arrays with sub-arrays in Python

Question

In my Python programming course, we are discussing how to manipulate (add,subtract,etc.) arrays and sub-arrays. An example from class was if we had

ourArray = [['a','b','c'],['e','f','g','h'],['i','j'],['k','l','m','n','o','p']...]

and Array = ['a','e','i','k',...], would something like ourArray-Array be possible?

I tried

for w in ourArray:
    w[0] - Array[0]

In the end, what I would like is

[['a','b','c'],['e','f','g','h'],['i','j'],['k','l','m','n','o','p']...] - ['a','e','i','k',...] = ['b','c'],['f','g','h'],['j'],['l','m','n','o','p']...].

Also, I am using Python 3 in Windows.

set difference sounds like what you want (but it doenst preserve order...) — Joran Beasley
– Joran Beasley, Commented Feb 3, 2015 at 19:12

Ofiris · Accepted Answer · 2015-02-03 19:27:22Z

2

How about this list comprehension, Pythonic, one liner:

>>> ourArray = [['a','b','c'],['e','f','g','h'],['i','j'],['k','l','m','n','o','p']]
>>> Array = ['a','e','i','k']
>>> [[item for item in arr if item not in Array] for arr in ourArray]
[['b', 'c'], ['f', 'g', 'h'], ['j'], ['l', 'm', 'n', 'o', 'p']]

For each array in ourArray, take only the items that are not in Array.

edited Feb 3, 2015 at 19:27

answered Feb 3, 2015 at 19:21

Ofiris

6,1716 gold badges38 silver badges59 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Bhargav Rao · Accepted Answer · 2015-02-03 19:16:10Z

1

You can always do the brute force method

>>> ourArray = [['a','b','c'],['e','f','g','h'],['i','j'],['k','l','m','n','o','p']]
>>> Array = ['a','e','i','k']
>>> for i in ourArray:
...     for j in i:
...          if j in Array:
...                i.remove(j)
... 
>>> ourArray
[['b', 'c'], ['f', 'g', 'h'], ['j'], ['l', 'm', 'n', 'o', 'p']]

answered Feb 3, 2015 at 19:16

Bhargav Rao

52.6k29 gold badges130 silver badges142 bronze badges

Collectives™ on Stack Overflow

Subtracting arrays from arrays with sub-arrays in Python

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related