You haven't created three different empty lists. You've created one empty list, and then created a new list with three references to that same empty list. To fix the problem use this code instead:
listy = [[] for i in range(3)]
Running your example code now gives the result you probably expected:
>>> listy = [[] for i in range(3)]
>>> listy[1] = [1,2]
>>> listy
[[], [1, 2], []]
>>> listy[1].append(3)
>>> listy
[[], [1, 2, 3], []]
>>> listy[2].append(1)
>>> listy
[[], [1, 2, 3], [1]]
GeeksforGeeks
geeksforgeeks.org › python › appending-to-2d-list-in-python
Appending to 2D List in Python - GeeksforGeeks
July 23, 2025 - This modifies the contents of the sublist while keeping the 2D structure intact. += operator allows you to extend a sublist with multiple elements in a concise manner. ... This is equivalent to using extend(). If we want to append multiple sublists dynamically list comprehension is a concise option.
Statistics Globe
statisticsglobe.com › home › python programming language for statistics & data science › append to 2d list in python (3 examples)
Extend 2D List in Python (3 Examples) | Append New Elements
April 5, 2023 - The code above is a concise way of writing my_2Dlist = my_2Dlist + [new_elem]. Once again, we wrapped the new element inside a pair of square brackets to keep the 2D structure of my_2Dlist.
Appending to 2D lists in Python - Stack Overflow
this is the most bizarre functionality ... in Python. seems almost like a bug. 2021-11-22T22:26:19.01Z+00:00 ... Save this answer. ... Show activity on this post. ... In other words, all three list references refer to the same list instance. ... Save this answer. ... Show activity on this post. Came here to see how to append an item to a 2D array, but ... More on stackoverflow.com
Two dimensional array in python - Stack Overflow
What you're using here are not arrays, but lists (of lists). If you want multidimensional arrays in Python, you can use Numpy arrays. You'd need to know the shape in advance. ... You try to append to second element in array, but it does not exist. More on stackoverflow.com
do you guys know how to add append an array in a 2d array?
my_list = [[1, 2, 3, 4, 5]] new_list = my_list * 5 print(new_list) Prints: [[1, 2, 3, 4, 5], [1, 2, 3, 4, 5], [1, 2, 3, 4, 5], [1, 2, 3, 4, 5], [1, 2, 3, 4, 5]] But be aware that this only creates multiple labels to the same [1, 2, 3, 4, 5] list object. Mutating any one of the inner lists mutates all of the inner lists as there is only one inner list object: new_list[0][0] += 40 print(new_list) print(my_list) # The original list object Prints: [[41, 2, 3, 4, 5], [41, 2, 3, 4, 5], [41, 2, 3, 4, 5], [41, 2, 3, 4, 5], [41, 2, 3, 4, 5]] [[41, 2, 3, 4, 5]] but you can reassign different objects within new_list: new_list[1] = [7,8,9] print(new_list) Prints: [[41, 2, 3, 4, 5], [7, 8, 9], [41, 2, 3, 4, 5], [41, 2, 3, 4, 5], [41, 2, 3, 4, 5]] If you actually want deep copies of the original inner list, you can use a list comprehension: my_list = [[1, 2, 3, 4, 5]] new_list = [my_list[0][:] for _ in range(5)] new_list[0][0] += 40 print(new_list) Prints: [[41, 2, 3, 4, 5], [1, 2, 3, 4, 5], [1, 2, 3, 4, 5], [1, 2, 3, 4, 5], [1, 2, 3, 4, 5]] More on reddit.com
5
5
February 19, 2024arrays - Python: multi-dimensional lists - appending one 2D list into another list - Stack Overflow
I'm looking to create a master array/list that takes several two dimensional lists and integrates them into the larger list. For example I have a TableA[] which has dates as one array/list and pri... More on stackoverflow.com
Dot Net Perls
dotnetperls.com › 2d-python
Python - 2D List Examples - Dot Net Perls
import time # Nested, 3x2. nested_list = [] nested_list.append([ ... Python supports a special "array" from the array module. An integer array is more compact in memory than an integer list. We can create a flattened 2D array.
Top answer 1 of 3
72
You haven't created three different empty lists. You've created one empty list, and then created a new list with three references to that same empty list. To fix the problem use this code instead:
listy = [[] for i in range(3)]
Running your example code now gives the result you probably expected:
>>> listy = [[] for i in range(3)]
>>> listy[1] = [1,2]
>>> listy
[[], [1, 2], []]
>>> listy[1].append(3)
>>> listy
[[], [1, 2, 3], []]
>>> listy[2].append(1)
>>> listy
[[], [1, 2, 3], [1]]
2 of 3
19
[[]]*3 is not the same as [[], [], []].
It's as if you'd said
a = []
listy = [a, a, a]
In other words, all three list references refer to the same list instance.
Delft Stack
delftstack.com › "delft stack" › "howto" › "python how-to's" › "how to append 2d array in python"
How to Append 2D Array in Python | Delft Stack
February 22, 2025 - Python’s built-in lists can represent 2D arrays as lists of lists. The simplest way to append values is using the append() method.
YouTube
youtube.com › watch
How Does Append Work With 2d Lists In Python - YouTube
In this python tutorial we are talking about lists in python! Specifically, we are answering the question of how does append work with 2d lists in python! Le...
Published: January 4, 2023
Top answer 1 of 12
91
You do not "declare" arrays or anything else in python. You simply assign to a (new) variable. If you want a multidimensional array, simply add a new array as an array element.
arr = []
arr.append([])
arr[0].append('aa1')
arr[0].append('aa2')
or
arr = []
arr.append(['aa1', 'aa2'])
2 of 12
82
There aren't multidimensional arrays as such in Python, what you have is a list containing other lists.
>>> arr = [[]]
>>> len(arr)
1
What you have done is declare a list containing a single list. So arr[0] contains a list but arr[1] is not defined.
You can define a list containing two lists as follows:
arr = [[],[]]
Or to define a longer list you could use:
>>> arr = [[] for _ in range(5)]
>>> arr
[[], [], [], [], []]
What you shouldn't do is this:
arr = [[]] * 3
As this puts the same list in all three places in the container list:
>>> arr[0].append('test')
>>> arr
[['test'], ['test'], ['test']]
Iditect
iditect.com › faq › python › appending-to-2d-lists-in-python.html
Appending to 2D lists in Python
matrix = [[1, 2, 3], [4, 5, 6]] new_row = [7, 8, 9] matrix.append(new_row) "Python extend 2D list" Description: This query involves extending a 2D list in Python with additional elements.
EyeHunts
tutorial.eyehunts.com › home › python 2d array append
Python 2D array append
June 27, 2023 - To append elements to a 2D array in Python, you can use the append() method available for Python lists. Here’s the syntax for appending elements to a 2D array: ... Here’s an example that demonstrates how to append elements to a 2D array (a list of lists) in Python:
Thedeveloperblog
thedeveloperblog.com › 2d-list-python
Python 2D List Examples
Jagged row lengths, where each row has a different number of elements, are also allowed. General idea. We create an empty list and add empty lists to it with append(). We can construct any rectangular (or jagged) list this way. In this example we built a 2 by 2 list.
IQCode
iqcode.com › code › python › python-2d-array-append
python 2d array append Code Example
temp_list = [[], [], [], []] temp_list[0].append("a1") temp_list[1].append("a2") temp_list[2].append("a3") tem...
Snakify
snakify.org › two-dimensional lists (arrays)
Two-dimensional lists (arrays) - Learn Python 3 - Snakify
An example of how you can do it: ... # the first line of input is the number of rows of the array n = int(input()) a = [] for i in range(n): a.append([int(j) for j in input().split()])
Reddit
reddit.com › r/learnpython › do you guys know how to add append an array in a 2d array?
r/learnpython on Reddit: do you guys know how to add append an array in a 2d array?
February 19, 2024 -
say i have array [[1,2,3,4,5]], how can i duplicate it 5 times to [[1,2,3,4,5],[1,2,3,4,5],[1,2,3,4,5],[1,2,3,4,5],[1,2,3,4,5]] ?
Top answer 1 of 4
1
my_list = [[1, 2, 3, 4, 5]] new_list = my_list * 5 print(new_list) Prints: [[1, 2, 3, 4, 5], [1, 2, 3, 4, 5], [1, 2, 3, 4, 5], [1, 2, 3, 4, 5], [1, 2, 3, 4, 5]] But be aware that this only creates multiple labels to the same [1, 2, 3, 4, 5] list object. Mutating any one of the inner lists mutates all of the inner lists as there is only one inner list object: new_list[0][0] += 40 print(new_list) print(my_list) # The original list object Prints: [[41, 2, 3, 4, 5], [41, 2, 3, 4, 5], [41, 2, 3, 4, 5], [41, 2, 3, 4, 5], [41, 2, 3, 4, 5]] [[41, 2, 3, 4, 5]] but you can reassign different objects within new_list: new_list[1] = [7,8,9] print(new_list) Prints: [[41, 2, 3, 4, 5], [7, 8, 9], [41, 2, 3, 4, 5], [41, 2, 3, 4, 5], [41, 2, 3, 4, 5]] If you actually want deep copies of the original inner list, you can use a list comprehension: my_list = [[1, 2, 3, 4, 5]] new_list = [my_list[0][:] for _ in range(5)] new_list[0][0] += 40 print(new_list) Prints: [[41, 2, 3, 4, 5], [1, 2, 3, 4, 5], [1, 2, 3, 4, 5], [1, 2, 3, 4, 5], [1, 2, 3, 4, 5]]
2 of 4
1
Easy way: x = your_list[0] for i in range(len(5)): your_list.append(x) Might be a more optimized way to do it but at least it should work
Python Pool
pythonpool.com › home › tutorials › python 2d lists: create, index, copy, flatten, and loop
Python 2d List: From Basic to Advance
July 14, 2026 - Do not call a Python 2D list a matrix without describing its shape and element contract. Clear invariants make indexing and validation much easier. Copy safely: Shallow row copies, aliasing, list multiplication, and deep copies. When the number of rows will grow over time, start with an empty outer list and append ...
Stack Overflow
stackoverflow.com › questions › 38064885 › python-multi-dimensional-lists-appending-one-2d-list-into-another-list
arrays - Python: multi-dimensional lists - appending one 2D list into another list - Stack Overflow
May 23, 2017 - Here's an example of one way to do it. TableA = [['01/01/2000', '$10'], ['02/01/2000', '$11']] If you entered this straight into the python interpreter, you'd define TableA as a list with two elements. Both of these elements are also lists.
LinkedIn
linkedin.com › pulse › two-dimensional-2d-lists-python-manish-v-
Two Dimensional (2D) Lists in Python
January 20, 2024 - Adding Rows: To add a new row to your 2D list, simply append a new list to the outer list.
Top answer 1 of 4
4
Simple, use + operator. You could concatenate two lists using + operator.
>>> list1 = [('a', '1'), ('b', '2'), ('c', '3')]
>>> list2 = [('d', '4'), ('e', '5'), ('f', '6')]
>>> list2 + list1
[('d', '4'), ('e', '5'), ('f', '6'), ('a', '1'), ('b', '2'), ('c', '3')]
2 of 4
4
You can use extend to modify list2 inplace:
>>> list2.extend(list1)
>>> list2
[('d', '4'), ('e', '5'), ('f', '6'), ('a', '1'), ('b', '2'), ('c', '3')]
This is particularly efficient if you're extending a large list, since no copy of that list is made: the operation is O(k) in complexity, where k is the length of the list you're adding on.
This is essentially the same behaviour as the code in your question that, as others have pointed out, should work. In practice extend should be a little faster because the loop over list1 is moved down to C level.
ValueError: too many values to unpack indicates that one or more of the tuples in your list final_list has more than two elements. This causes the line for x, y in final_list: to raise the error since x and y can't label every element in the tuple.
Top answer 1 of 5
7
You can just extend your list.
data = []
data.extend(d1)
data.extend(d2)
data.extend(d3)
2 of 5
5
Simply write:
all_data = data_1 + data_2 + data_3
If you want to merge all the corresponding sublists of these lists, you can write:
# function that merges all sublists in single list
def flatten(l):
return [el for subl in l for el in subl]
# zipped - is a list of tuples of corresponding items (our deep sublists) of all the lists
zipped = zip(data_1, data_3, data_3)
# merge tuples to get single list of rearranges sublists
all_data = flatten(zipped)