Removing specific elements from a list and appending in Python

I have a list J[0]. I am removing [1] from this list and creating J[1]. Now I wish to append J[0],J[1] into J. But I am getting an error. I present the expected output.

J=[]
for t in range(0,2):
    J[0] = [[1, 3, 7, 9]]
    J[1]=J.remove([1])
    
print("New J:", J[t])

The error is

in <module>
    J[0] = [[1, 3, 7, 9]]

IndexError: list assignment index out of range

The expected output is

[[1, 3, 7, 9],[3, 7, 9]]

Since you have initialized J to be an empty list, you cannot access the J[0] element and that is the reason for the IndexError. You first have to append new elements to J in order to access them.

The way to make your code work could be as follows:

J=list()
l = [1, 3, 7, 9]     # Assigning list to variable l
l_removed = l.copy() # Making a copy of l in order to avoid manipulating it
J.append(l)          # Appending l to J
l_removed.remove(1)  # Removing the 1 from the copied list
J.append(l_removed)  # Appending the new list to J
print(J)

Here is the output of the above code block:

[[1, 3, 7, 9], [3, 7, 9]]

I think you are getting confused by the levels of nested lists and by indexes. Eg. You are starting with an empty list J. You assign then a list containing a list to the zeroth entry of that list.
You are trying to remove a list containing 1 from J, whivh is not there.
You are trying to do this two times with the for loop.

I guess what you want, could be something like this:

j = [[1, 3, 7, 9]]
j_new = j[0].copy()
j_new.pop(0)
j.append(j_new)
print(j)

You could do it like this:

J = []

for _ in range(2):
    J.append([1, 3, 7, 9])

J[-1].pop(0)

print(J)

Output:

[[1, 3, 7, 9], [3, 7, 9]]

Or:

Rather than deleting the element, don't put it in the list - e.g.,

J = []

for i in range(2):
    J.append([1, 3, 7, 9][i:])

print(J)