You can use:
>>> lst = [None] * 5
>>> lst
[None, None, None, None, None]
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You can use:
>>> lst = [None] * 5
>>> lst
[None, None, None, None, None]
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Why don't these questions get answered with the obvious answer?
a = numpy.empty(n, dtype=object)
This creates an array of length n that can store objects. It can't be resized or appended to. In particular, it doesn't waste space by padding its length. This is the Python equivalent of Java's
Object[] a = new Object[n];
If you're really interested in performance and space and know that your array will only store certain numeric types then you can change the dtype argument to some other value like int. Then numpy will pack these elements directly into the array rather than making the array reference int objects.
AskPython
askpython.com › home › 3 ways to initialize a python array
3 ways to initialize a Python Array - AskPython
January 16, 2024 - Python NumPy module can be used to create arrays and manipulate the data in it efficiently. The numpy.empty() function creates an array of a specified size with a default value = ‘None’.
python - Create an array of size n with initialized value - Stack Overflow
In python, it's possible to create an array of size n with [] * n or even initialize a fixed value for all items with [0] * n. Is it possible to do something similar but initialize the value with ... More on stackoverflow.com
python - initialize a numpy array - Stack Overflow
Is there way to initialize a numpy array of a shape and add to it? I will explain what I need with a list example. If I want to create a list of objects generated in a loop, I can do: a = [] for i... More on stackoverflow.com
learning to declare and initialize arrays in a single line of code
okay i like LINQ. Like... a lot. To a problematic degree. But this is a fucking war crime. Bro woke up and didn't choose violence. They chose genocide. More on reddit.com
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December 30, 2024Is it possible to create an array in python?
I noticed that python uses Linked Lists by default It does not. Python's list type is a dynamically growing array, similar to vectors in C++, ArrayLists in Java, Lists in C# or arrays in Ruby, Perl, PHP or JavaScript. More on reddit.com
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May 2, 2024Videos
Quora
quora.com › In-Python-how-can-I-initialize-an-array-or-list-yet-to-be-populated-with-values-to-have-a-defined-size
In Python, how can I initialize an array (or list), yet to be populated with values, to have a defined size? - Quora
True: you didn’t find any contradictions; this behavior is standard in the Python library and most other collections libraries I’ve worked with · False: a kind of soft error indicator for an empty input ... raise an exception: raising exceptions is effectively an output value - just one that gets handled differently from normal program flow ... It’s easy enough to modify both to get true: just return True if the collection is empty right off the bat. ... RelatedHow do I initialize an array with a specific size in Python (like Roblox Luau's table.create (size, value) or LuaJIT's table.new (size, value) for example)?
GeeksforGeeks
geeksforgeeks.org › python › python-initialize-empty-array-of-given-length
Python - Initialize empty array of given length - GeeksforGeeks
# initialize the spaces with 0’s with # the help of list comprehensions a = [0 for x in range(10)] print(a) b = [[0] * 4 for i in range(3)] print(b) ... In this example, we are using a Python loop for 1D and 2D empty arrays. ... In this method, we are using the Numpy module to generate an empty matrix of 1D and 2D sizes using np.empty().
Published July 12, 2025
Python
docs.python.org › 3 › library › array.html
array — Efficient arrays of numeric values
The actual size can be accessed through the array.itemsize attribute. ... A string with all available type codes. ... A new array whose items are restricted by typecode, and initialized from the optional initializer value, which must be a bytes or bytearray object, a Unicode string, or iterable over elements of the appropriate type.
Note.nkmk.me
note.nkmk.me › home › python
Initialize a List of Any Size with Specific Values in Python | note.nkmk.me
August 20, 2023 - This article explains how to initialize a list of any size (number of elements) with specific values in Python. ... See the following article about initializing a NumPy array (numpy.ndarray).
Java2Blog
java2blog.com › home › python › python array › how to initialize array in python
How to initialize array in Python - Java2Blog
November 20, 2020 - here, empty() method of numpy is used to create a numpy array of given size with default value None. ... That’s all about how to initialize array in Python.
FavTutor
favtutor.com › blogs › how-to-initialize-an-array-in-python
How to Initialize an Array in Python? (with Code) | FavTutor
January 27, 2021 - Python language has many inbuilt libraries and functions which makes our task easier and simpler in comparison to other programming languages. NumPy module is one of them. NumPy module can be used to initialize the array and manipulate the data stored in it. The number.empty() function of the NumPy module creates an array of a specified size with the default value=” None”.
W3Schools
w3schools.com › python › python_arrays.asp
Python Arrays
Note: Python does not have built-in support for Arrays, but Python Lists can be used instead. Note: This page shows you how to use LISTS as ARRAYS, however, to work with arrays in Python you will have to import a library, like the NumPy library.
Quora
quora.com › How-do-I-create-an-array-of-a-specific-size-in-Python
How to create an array of a specific size in Python - Quora
Answer (1 of 3): (1) In Python, you don’t typically work with arrays, but with lists. There are libraries to work with arrays, but you only use them for certain specialized purposes. Such as when you need matrix multiplication or some other advanced math, and want to do it quickly.
Kristianeschenburg
kristianeschenburg.github.io › 2019 › 08 › list-size
Quick Note: Initialize Python List With Prespecified Size - A Rambling On
August 21, 2019 - The base arrays are generally associated with a size or length parameter, that initializes the array to a certain length.
Python Guides
pythonguides.com › initialize-an-array-in-python
How To Initialize An Array In Python?
March 19, 2025 - Learn how to initialize arrays in Python using methods like list comprehensions, NumPy's functions, and array modules. Step-by-step examples for various sizes.
Iditect
iditect.com › faq › python › initialising-an-array-of-fixed-size-in-python.html
Initialising an array of fixed size in Python
In Python, you can initialize an array (or a list) of a fixed size by using list comprehensions or by repeating a specific value.
Top answer 1 of 14
227
numpy.zerosReturn a new array of given shape and type, filled with zeros.
or
numpy.onesReturn a new array of given shape and type, filled with ones.
or
numpy.emptyReturn a new array of given shape and type, without initializing entries.
However, the mentality in which we construct an array by appending elements to a list is not much used in numpy, because it's less efficient (numpy datatypes are much closer to the underlying C arrays). Instead, you should preallocate the array to the size that you need it to be, and then fill in the rows. You can use numpy.append if you must, though.
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The way I usually do that is by creating a regular list, then append my stuff into it, and finally transform the list to a numpy array as follows :
import numpy as np
big_array = [] # empty regular list
for i in range(5):
arr = i*np.ones((2,4)) # for instance
big_array.append(arr)
big_np_array = np.array(big_array) # transformed to a numpy array
of course your final object takes twice the space in the memory at the creation step, but appending on python list is very fast, and creation using np.array() also.
Career Karma
careerkarma.com › blog › python › python: initialize list of size n
Python: Initialize List of Size N: A Complete Guide | Career Karma
December 1, 2023 - To initialize a list of size n in Python, you can use multiplication syntax or a range() statement. On Career Karma, learn how to initialize empty lists of custom sizes.
TutorialsPoint
tutorialspoint.com › article › how-to-initialize-an-empty-array-of-given-length-using-python
How to Initialize an Empty Array of given Length using Python
March 27, 2026 - Use multiplication operator [None] * length for simple empty arrays. For numerical computations, prefer NumPy's empty() function. List comprehension offers flexibility for complex initialization patterns.
CodeRivers
coderivers.org › blog › how-to-initialize-array-in-python
Initializing Arrays in Python: A Comprehensive Guide - CodeRivers
February 22, 2026 - You can directly initialize a list with specific elements by separating them with commas inside the square brackets: my_array = [10, 20, 30, 'apple', 'banana'] print(my_array) ... The array module in Python provides an array type which is more space-efficient than a list when storing homogeneous ...
CodeRivers
coderivers.org › blog › array-python-initialize
Python Array Initialization: A Comprehensive Guide - CodeRivers
February 22, 2026 - In Python, lists can be used as a simple form of arrays. Lists are versatile and can store elements of different data types, although for array-like behavior, it's often better to keep elements of the same type. # Initializing a list (array) with elements my_list = [1, 2, 3, 4, 5] print(my_list) # Initializing an empty list empty_list = [] print(empty_list)
Studytonight
studytonight.com › python-howtos › how-to-declare-an-array-in-python
How to declare an array in Python - Studytonight
In the code example above, both arr1 and arr2 have size 3. Q. How to fill array in Python? There are many ways to create an array in Python and fill an array with values in Python. You can use the literal style using a Python list, or use a for loop to set values, of use the array module in Python to create an array and fill values in the array in Python. ... # fill values using for loop arr1 = [0 for i in range(5)] # fill values using literal style arr2 = [1, 2, 3, 4, 5] # using initializer arr3 = [0] * 2