Related Articles

Python – Initialize empty array of given length

• Difficulty Level : Basic
• Last Updated : 06 Dec, 2019

Prerequisite: List in Python

As we know Array is a collection of items stored at contiguous memory locations. In Python, List (Dynamic Array) can be treated as Array. In this article, we will learn how to initialize an empty array of some given size.

Let’s see different Pythonic ways to do this task.

Method 1 –

Syntax:

```list1 = [0] * size
list2 = [None] * size
```
 `# initializes all the 10 spaces with 0’s``a ``=` `[``0``] ``*` `10` ` ` `# initializes all the 10 spaces with None``b ``=` `[``None``] ``*` `10` ` ` `# initializes all the 10 spaces with A's``c ``=` `[``'A'``] ``*` `5` ` ` `# empty list which is not null, it's just empty.``d ``=` `[] `` ` `print` `(a, ``"\n"``, b, ``"\n"``, c, ``"\n"``, d);`
Output:
```[0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
[None, None, None, None, None, None, None, None, None, None]
['A', 'A', 'A', 'A', 'A']
[]
```

Method 2 – Use loops just like C and assign the size.

Syntax:

```a = [0 for x in range(size)] #using loops
```
 `a ``=` `[]``b ``=` `[]`` ` `# initialize the spaces with 0’s with ``# the help of list comprehensions``a ``=` `[``0` `for` `x ``in` `range``(``10``)]``print``(a)`` ` `# initialize multi-array ``b ``=` `[ [ ``None` `for` `y ``in` `range``( ``2` `) ]``             ``for` `x ``in` `range``( ``2` `) ]``              ` `print``(b)`
Output:
```[0, 0, 0, 0, 0, 0, 0, 0, 0, 0]

[[None, None], [None, None]]
```

Method 3 – Using Numpy to create empty array.

 `import` `numpy`` ` `# create a simple array with numpy empty()``a ``=` `numpy.empty(``5``, dtype``=``object``)``print``(a)`` ` `# create multi-dim array by providing shape``matrix ``=` `numpy.empty(shape``=``(``2``,``5``),dtype``=``'object'``)``print``(matrix)`

Output:

```[None None None None None]

[[None None None None None]
[None None None None None]]
```

Attention geek! Strengthen your foundations with the Python Programming Foundation Course and learn the basics.

To begin with, your interview preparations Enhance your Data Structures concepts with the Python DS Course. And to begin with your Machine Learning Journey, join the Machine Learning – Basic Level Course

My Personal Notes arrow_drop_up