# Declare and Initialize an Array (List) in Python

> Create arrays in Python using list literals, the list() constructor, or the array module for type-restricted collections, with examples for each approach

**URL:** https://sentry.io/answers/declare-an-array-in-python/

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## The Problem

How do I declare an array in Python?

## The Solution

The default array type in Python is known as a *list*. To create a new empty list and assign it to a variable, we can use either of the following equivalent lines:

```python
my_list = []
my_list = list()
```

We don't have to instantiate our list as empty but can add any number of items of any type to it.

```python
my_list = [1, "hello", True]
```

To create a list with many copies of the same value, we can use the multiplication operator:

```python
my_list = [0] * 10  # will create a list containing ten 0s.
```
Note, using this syntax for more complex types can cause issues as the list is created as a reference copy.

```python
basic = [1]
my_list = [basic]*10
print(my_list)    # [[1], [1], [1], [1], [1], [1], [1], [1], [1], [1]]
basic[0] = 2
print(my_list)    # [[2], [2], [2], [2], [2], [2], [2], [2], [2], [2]]
```

Lists in Python can contain elements of different data types and do not have a predefined length. Python provides an [`array`](https://docs.python.org/3.10/library/array.html) module that can be used to create lists that can only contain one type of element, though they can also be of arbitrary and varying lengths.

```python
from array import array

my_int_array = array('i', [1, 2, 3, 4, 5])  # create an array of signed integers
my_int_array.append(6)  # will add 6 to the end of the array
my_int_array.append('a')  # will throw a TypeError: an integer is required (got type str)
```

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*Source: [sentry.io/answers/declare-an-array-in-python/](https://sentry.io/answers/declare-an-array-in-python/)*