CODEWITHSUNDEEP
pythonpython-3.x
Jane P
Jane P

Reputation: 99

Remove elements from a nested list

I am new to python and learning about the lists. I am trying to create a function that will remove a specific value from the list. I know there is a .remove() function to remove elements but it doesn't work on the nested list.

def remove(list, x):
   if x in list:  
      return list.remove(x)

mylist = [[1, 2, 3, 2, 4, 8, 2],2] 
remove(mylist, 2) 
print(mylist)

The result I'd like to get:

[1, 3, 4, 8]

Appreciate your help in advance

Upvotes: 1

Views: 3491

Answers (2)

najeem
najeem

Reputation: 1921

It is not clear from your example whether you really want a flattened list as output or a you'd like to still keep the structure of your list. And also how many levels of nesting you will have. So I have written a recursive function which will remove item from a deeply nested list without flattening as well as flattening the output.

To make my solutions clear, I have modified your input list to the following.

mylist = [[1, 2, 3, 2, 4, 8, 2],2,3,34,2,[[3,4],3,[1,2]]]

Function

def rem_list_item(l, remval, flatten=False):
    """Recursive function to remove an item from a nested list"""
    flatlist = []
    for item in l:
        if isinstance(item, list):
            # Calling the function itself recursively if the item
            # is a list. 
            if flatten:
                # += will make sure the list is appended without nesting.
                flatlist+=rem_list_item(item, remval, flatten=True)
            else:
                # appended the sublist so that nesting is preserved
                flatlist.append(rem_list_item(item, remval, flatten=False))
        else:
            # If the item is not a list, just append it to the return list
            if item != remval:
                flatlist.append(item)
    return flatlist

Without flattening

rem_list_item(mylist, 2, flatten=False)
Out: [[1, 3, 4, 8], 3, 34, [[3, 4], 3, [1]]]

With flattening

rem_list_item(mylist, 2, flatten=True)
Out: [1, 3, 4, 8, 3, 34, 3, 4, 3, 1]

Upvotes: 3

Nasser Ali Karimi
Nasser Ali Karimi

Reputation: 4663

I customize your code here you can see an online version https://onlinegdb.com/Sk2oA9KGV

Continue and read the description if you don't understand

def remove(list, x):
       if x in list:  
          return list.remove(x)
          
    mylist = [[1, 2, 3, 2, 4, 8, 2],2]
    for i in range(len(mylist)):
        
        if isinstance(mylist[i], list) == True : 
            mylist[i] = list(set(mylist[i]))
            mylist[i].remove(2)
            mylist[i].sort()
        else : 
            if mylist[i] == 2 : 
                del mylist[i]
    print(mylist)
    print()

the final result is like this

print(mylist)

[[1, 3, 4, 8]]

print(mylist[0])

[1, 3, 4, 8]


Complete description

First of all, you need to use for loop to separate the arrays in a multidimensional array

for i in range(len(mylist)):

Then you should check that the current variable that you have is array or not

if isinstance(mylist[i], list) == True :

If the condition being True then you continue To remove duplicate items here 2 you need to this line

mylist[i] = list(set(mylist[i]))

And then run your remove funtion

mylist[i].remove(2)

After this, your result will be like this [8, 1, 3, 4] Then you should sort your array by this code

mylist[i].sort()

And one more thing that if your variable was not arrayed you should check that if it is matched with your item that you want delete it or not if match then delete that

if mylist[i] == 2 : 
     del mylist[i]

Upvotes: 4

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