You're technically trying to index an uninitialized array. You have to first initialize the outer list with lists before adding items; Python calls this "list comprehension".
# Creates a list containing 5 lists, each of 8 items, all set to 0
w, h = 8, 5
Matrix = [[0 for x in range(w)] for y in range(h)]
#You can now add items to the list:
Matrix[0][0] = 1
Matrix[6][0] = 3 # error! range...
Matrix[0][6] = 3 # valid
Note that the matrix is "y" address major, in other words, the "y index" comes before the "x index".
print Matrix[0][0] # prints 1
x, y = 0, 6
print Matrix[x][y] # prints 3; be careful with indexing!
Although you can name them as you wish, I look at it this way to avoid some confusion that could arise with the indexing, if you use "x" for both the inner and outer lists, and want a non-square Matrix.
Answer from Manny D on Stack OverflowTutorialsPoint
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Python 2D Array
February 21, 2009 - Consider the example of recording temperatures 4 times a day, every day. Some times the recording instrument may be faulty and we fail to record data. Such data for 4 days can be presented as a two dimensional array as below.
GeeksforGeeks
geeksforgeeks.org › python › python-using-2d-arrays-lists-the-right-way
Using 2D arrays/lists in Python - GeeksforGeeks
If we assign the 0th index to another integer say 1, then a new integer object is created with the value of 1 and then the 0th index now points to this new int object as shown below · Similarly, when we create a 2d array as "arr = [[0]*cols]*rows" ...
Published December 20, 2025
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Python 2D collections are easy! ⬜ - YouTube
Python 2D arrays and lists - YouTube
GCSE Computer Science - Python 2D List / 2D Array / Iteration
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iGCSE Computer Science - Python - 2D Arrays - YouTube
Create a Matrix (2D array) in NumPy Python | Module NumPy ...
Top answer 1 of 16
1261
You're technically trying to index an uninitialized array. You have to first initialize the outer list with lists before adding items; Python calls this "list comprehension".
# Creates a list containing 5 lists, each of 8 items, all set to 0
w, h = 8, 5
Matrix = [[0 for x in range(w)] for y in range(h)]
#You can now add items to the list:
Matrix[0][0] = 1
Matrix[6][0] = 3 # error! range...
Matrix[0][6] = 3 # valid
Note that the matrix is "y" address major, in other words, the "y index" comes before the "x index".
print Matrix[0][0] # prints 1
x, y = 0, 6
print Matrix[x][y] # prints 3; be careful with indexing!
Although you can name them as you wish, I look at it this way to avoid some confusion that could arise with the indexing, if you use "x" for both the inner and outer lists, and want a non-square Matrix.
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If you really want a matrix, you might be better off using numpy. Matrix operations in numpy most often use an array type with two dimensions. There are many ways to create a new array; one of the most useful is the zeros function, which takes a shape parameter and returns an array of the given shape, with the values initialized to zero:
>>> import numpy
>>> numpy.zeros((5, 5))
array([[ 0., 0., 0., 0., 0.],
[ 0., 0., 0., 0., 0.],
[ 0., 0., 0., 0., 0.],
[ 0., 0., 0., 0., 0.],
[ 0., 0., 0., 0., 0.]])
Here are some other ways to create 2-d arrays and matrices (with output removed for compactness):
numpy.arange(25).reshape((5, 5)) # create a 1-d range and reshape
numpy.array(range(25)).reshape((5, 5)) # pass a Python range and reshape
numpy.array([5] * 25).reshape((5, 5)) # pass a Python list and reshape
numpy.empty((5, 5)) # allocate, but don't initialize
numpy.ones((5, 5)) # initialize with ones
numpy provides a matrix type as well, but it is no longer recommended for any use, and may be removed from numpy in the future.
Snakify
snakify.org › two-dimensional lists (arrays)
Two-dimensional lists (arrays) - Learn Python 3 - Snakify
And suppose you have to set elements of the main diagonal equal to 1 (that is, those elements a[i][j] for which i==j), to set elements above than that diagonal equal to 0, and to set elements below that diagonal equal to 2. That is, you need to produce such an array (example for n==4):
Scaler
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2D Array in Python | Python Two-Dimensional Array - Scaler Topics
October 10, 2025 - Where arr_name is the name of the 2D array in which the deletion is to be done, and ind is the index of the element to be deleted. In this example, we have deleted the value in the 2nd column in the 1st row. It causes the values after it to be shifted one index back. ... In this example, we delete the array at index 1 in the outer array. It causes the internal arrays after it to be shifted one index back. ... We have seen above that Python 2D arrays are stored linearly in memory.
Google
sites.google.com › rgc.aberdeen.sch.uk › rgcahcomputingrevision › software-design › data-types-and-structures › 2d-arrays
Advanced Higher Computing Revision - 2D Arrays
Python treats this as a list within a list. You will notice that we have initialised each element in the array with a value of 0. This would create a 2D array called my2dArray with 3 rows and 8 columns.
Guru99
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Python 2D Arrays: Two-Dimensional List Examples
August 12, 2024 - Example: Creare 2D array with 4 rows and 5 columns array=[[23,45,43,23,45],[45,67,54,32,45],[89,90,87,65,44],[23,45,67,32,10]] #use for loop to iterate the array for rows in array: for columns in rows: print(columns,end=" ") print() Output: ...
CodeSignal
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A Beginner's Guide to Multidimensional Arrays in Python
In this example, array is a 2-dimensional array, just like a 3-storey 'apartment building,' where every floor is an inner list. ... All indices in Python arrays are 0-based. Let's say you want to visit an apartment on the second floor (index 1) and bring a package to the first unit (index 0) ...
Drbeane
drbeane.github.io › python_dsci › pages › array_2d.html
2-Dimensional Arrays — Python for Data Science
In the following example, we reshape a 1D array into a 2D array with a single row, as well a 2D array with a single column.
Sentry
sentry.io › sentry answers › python › define a two-dimensional array in python
Define a two-dimensional array in Python | Sentry
The Problem How can I create an empty two-dimensional array in Python, e.g. for matrix operations? The Solution The best way to create two-dimensional (2D…
Javatpoint
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Python 2D array - Javatpoint
Python 2D array with python, tutorial, tkinter, button, overview, entry, checkbutton, canvas, frame, environment set-up, first python program, operators, etc.
GeeksforGeeks
geeksforgeeks.org › python-using-2d-arrays-lists-the-right-way
Python | Using 2D arrays/lists the right way - GeeksforGeeks
The code then shows another approach using a nested list comprehension to create the 2D array arr. This method avoids aliasing by creating a new list for each row, resulting in a proper 2D array. ... # Python 3 program to demonstrate working # of method 1 and method 2.
Published June 20, 2024
Cf
physics-python.astro.cf.ac.uk › Week6
PX1224 -Week6: Two Dimensional Arrays
To generate an image like this, we first want to create x and y arrays using mgrid(), then calculate a "height" value, z, at each point in x and y. Finally, we plot a contour plot using the values of z to give the colours. The code to do this is given below · Python can show such images. The example code below produces a large 2D array, and then produces a pattern in it.
iO Flood
ioflood.com › blog › python-2d-array
Python 2D Array with Lists | Guide (With Examples)
February 10, 2024 - In this example, we’ve created a 2D array where each element is the product of its row and column indices (starting from 1). The outer list comprehension (for i in range(1, 4)) creates the rows, and the inner list comprehension (for j in range(1, ...
Python.org
discuss.python.org › python help
Need help with a two-dimensional array - Python Help - Discussions on Python.org
June 2, 2022 - Here’s what I have: 1 2 3 4 5 6 7 8 A X X X X X X X X B X X X X X T X X C X X X X X X X X D X X X X X X X X E X X X X X X X X F X X X X X X X X G X X X X X X X X H X X X X X X X X This is a simple two-dimensional array.
NumPy
numpy.org › devdocs › user › absolute_beginners.html
NumPy: the absolute basics for beginners — NumPy v2.5.dev0 Manual
To add the rows or the columns in a 2D array, you would specify the axis. ... Learn more about basic operations here. There are times when you might want to carry out an operation between an array and a single number (also called an operation between a vector and a scalar) or between arrays of two different sizes. For example, your array (we’ll call it “data”) might contain information about distance in miles but you want to convert the information to kilometers.
DataCamp
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2D NumPy Arrays | Python
If you ask for the type of these arrays, Python tells you that they are numpy.ndarray. numpy dot tells you it's a type that was defined in the numpy package. ndarray stands for n-dimensional array. The arrays np_height and np_weight are one-dimensional arrays, but it's perfectly possible to create 2 dimensional, three dimensional, heck even seven dimensional arrays! Let's stick to 2 in this video though. You can create a 2D numpy array from a regular Python list of lists.
AskPython
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Two Dimensional Array in Python - AskPython
August 6, 2022 - Syntax: <slice_array> = <array>[start:stop] array1 = [[1,2,3],[4,5,6,7]] #python array slice array2 = array1[1:3] #index 1 to 2 print(array2) array2 = array1[:1] #index 0 to 1 print(array2) Output: Output-Slicing 2D Array ·
Medium
medium.com › @izxxr › 2d-arrays-in-python-08ff7c287b2a
2D Arrays in Python. 2D arrays, also known as a matrix, are… ...
September 7, 2024 - To represent 2D arrays in pure Python without any additional dependencies, we use the list-in-list approach. table = [ [1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12], ] This is a 2D array with three rows and four columns.
w3resource
w3resource.com › python-exercises › python-conditional-exercise-11.php
Python Exercise: Generates a two-dimensional array - w3resource
Write a Python program that takes two digits m (row) and n (column) as input and generates a two-dimensional array. The element value in the i-th row and j-th column of the array should be i*j. Note : i = 0,1.., m-1 j = 0,1, n-1. ... # Prompt ...
