Use list item index as index to another list in python

Question

I have two lists:

A = ['PA', 'AT', 'TR']
removlistv = ['TR', 'AI', 'IO', 'SO', 'CR', 'PH', 'RT']

I find the intersection of the two lists:

rm_nodes = set(A) & set(removelistv)

Which creates the set {'TR'}. I now want to find the index of that intersection (or intersections) in the list removelistv:

indices = [removelistv.index(x) for x in rm_nodes]

So far so good, indices contains the correct value. The problem starts when I want to use the index value (which in this case is [0] i.e. a list) to retrieve the matching item in a third list removelistst = ['TR0', 'AI1', 'IO1', 'SO0', 'CR1', 'PH0', 'RT1']. My goal is to remove the item 'TR0' from removelistst. Basically, I want to remove items from this list based on the output of the intersection of the two lists in the beginning.

I've tried the following:

numbers =[ int(x) for x in indices ]
removelistst[numbers]

Which returns the error:

TypeError: list indices must be integers or slices, not list

Can't you just do removelistst.remove(value + str(index))? — kennysliding
– kennysliding, Commented Nov 23, 2020 at 16:08

Barmar · Accepted Answer · 2020-11-23 16:12:42Z

4

Loop through indices and pop the specified element out of removelistst.

for index in sorted(indices, reverse=True):
    removelistst.pop(index)

I sort indices in reverse so that removing an element won't affect the indexes of later elements to be removed.

answered Nov 23, 2020 at 16:12

Barmar

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1 Comment

jonna_983 Over a year ago

Thanks, I tried it out without sorting to observe the problem.

Bill Lynch · Accepted Answer · 2020-11-23 16:14:06Z

2

There's lots of ways to do this, here's a list comprehension:

removelistst = [value for index, value in enumerate(removelistst) if index not in numbers]

answered Nov 23, 2020 at 16:14

Bill Lynch

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