CODEWITHSUNDEEP
pythonarrays
Allan
Allan

Reputation: 47

Python | How to remove sub array from 2D array

If I have a 2D array like:

array = [["hello"], [1,2,3], [4,5,6]]

How can I get the program to remove the first sub array so that it turns out like this:

array = [[1,2,3], [4,5,6]]

If I try to do array[0].pop[0], the array ends up like this:

array = [[], [1,2,3], [4,5,6]]

Upvotes: 1

Views: 8982

Answers (5)

Eugene Yarmash
Eugene Yarmash

Reputation: 149776

To remove the first item from array and return it use array.pop(0):

>>> array = [["hello"], [1,2,3], [4,5,6]]
>>> array.pop(0)
['hello']
>>> array
[[1, 2, 3], [4, 5, 6]]

If you're not interested in the return value, you can use slice assignment or del. These can be used to remove more than one item.

>>> array = [["hello"], [1,2,3], [4,5,6]]
>>> array[:1] = []
>>> array
[[1, 2, 3], [4, 5, 6]]

Upvotes: 0

Ohad Eytan
Ohad Eytan

Reputation: 8464

array[0] is the list ["hello"], the first (and only) item in this list is the string "hello", so if you pop it you get the empty list [], hence you get your result.

As mentioned the right way to pop the first list from array is array.pop(0)

Upvotes: 0

dnit13
dnit13

Reputation: 2496

When you do array[0].pop(0) you are removing "hello" not ["hello"] Since ["hello"] is at position 0 of array you should use

array.pop(0)

Upvotes: 2

Francisco
Francisco

Reputation: 11476

You must do

array.pop(0)

Since you want to remove the first element

Upvotes: 3

Kasravnd
Kasravnd

Reputation: 107287

You are deleting the first item of the first sub list, not whole of the sub list. You can use del statement to delete the first item:

>>> array=[["hello"],[1,2,3],[4,5,6]]
>>> 
>>> del array[0]
>>> 
>>> array
[[1, 2, 3], [4, 5, 6]]

Or if you want to preserve the deleted item you can use array.pop(0).

Upvotes: 0

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