Python Arrays

In this article, you will learn about Python arrays, the differences between arrays and lists, and how and when to use them with examples.

In programming, an array is a collection of elements of the same type.

arrays in Java, C / C ++It is very popular in most programming languages such as JavaScript. However, in Python, they are not common. When people talk about Python arrays, they are actually talking about Python lists. If you don't know what a list is, you should definitely check outPython listarticle.

Python list and array module as array

We can consider a list as an array. However, we cannot restrict the type of elements stored in the list. For example:

a = [1,　3.5, "Hello"]

If an array is created using the array module, all elements of the array must be of the same numeric type.

import　array　as　arr
a = arr.array('d', [1,　3.5, "Hello"])　　　//　Error

How to create an array?

You may have guessed from the above example that we need to import the array module to create an array. For example:

import　array　as　arr
a = arr.array('d', [1.1,　3.5,　4.5])
print(a)

Here, we create a float type array. The letter 'd' is the type code. This determines the type of the array during the creation process.

Common type codes:

We will not discuss different C types in this article. Throughout the article, we will use two type codes: 'i' for integers and 'd' for floating-point numbers.

Note: 'u' since version3.3starting, it is not recommended to use the type code for Unicode characters. Try to avoid using it.

How to access array elements?

We use indices to access elements of an array:

import　array　as　arr
a = arr.array('i', [2,　4,　6,　8])
print("First element:", a[0])
print("Second element:", a[1])
print("Last element:", a[-1])

Remember, the index starts from 0 (not1）beginning, similar to a list.

How to slice an array?

We can use the slicing operator to access a series of items in an array:.

import　array　as　arr
numbers_list = [2,　5,　62,　5,　42,　52,　48,　5]
numbers_array = arr.array('i', numbers_list)
print(numbers_array[2:5]) # The3-the5elements
print(numbers_array[:-5]) # From the beginning to the4elements
print(numbers_array[5:]) # From the6elements to the end
print(numbers_array[:]) # From the beginning to the end

When running the program, the output is:

array('i', [62,　5,　42])
array('i', [2,　5,　62])
array('i', [52,　48,　5])
array('i', [2,　5,　62,　5,　42,　52,　48,　5])

How to change or add elements?

Arrays are mutable; their elements can be changed in a way similar to lists.

import　array　as　arr
numbers　=　arr.array('i',　[1,　2,　3,　5,　7,　10])
# Change the first element
numbers[0] = 0　　　　
print(numbers) # Output: array('i', [0,　2,　3,　5,　7,　10])
# Change the3to the5elements
numbers[2:5]) = arr.array('i', [4,　6,　8])　　　
print(numbers) # Output: array('i', [0,　2,　4,　6,　8,　10])

We can use the append() method to add an item to a list, or use the extend() method to add multiple items to a list.

import　array　as　arr
numbers　=　arr.array('i',　[1,　2,　3])
numbers.append(4))
print(numbers)　　　　　#　Output:　array('i',　[1,　2,　3,　4])
#　extend() appends an iterable to the end of the array
numbers.extend([5,　6,　7])　
print(numbers)　　　　　#　Output:　array('i',　[1,　2,　3,　4,　5,　6,　7])

We can use+The operator connects two arrays.

import　array　as　arr
odd　=　arr.array('i',　[1,　3,　5])
even　=　arr.array('i',　[2,　4,　6])
numbers　=　arr.array('i')　　　#　Create an empty integer array
numbers　=　odd　+　even
print(numbers)

How to remove/Delete element?

We can usePython's del statementRemove one or more items from an array.

import　array　as　arr
number　=　arr.array('i',　[1,　2,　3,　3,　4])
del　number[2]　#　Delete the third element
print(number)　#　Output:　array('i',　[1,　2,　3,　4])
del　number　#　Delete the entire array
print(number)　#　Error: array is not defined

We can use the remove() method to delete a given item, or use the method to delete the item at a specified index pop().

import　array　as　arr
numbers　=　arr.array('i',　[10,　11,　12,　12,　13])
numbers.remove(12))
print(numbers)　　　#　Output:　array('i',　[10,　11,　12,　13])
print(numbers.pop(2))　　　#　Output:　12
print(numbers)　　　#　Output:　array('i',　[10,　11,　13])

When to use an array?

lists are much more flexible than arrays. They can store elements of different data types, including strings. Moreover, lists are faster than arrays. Moreover, if you need to perform mathematical calculations on arrays and matrices, it is best to useNumPymethods of libraries and the like.

Do not use them unless you really need an array (it may be necessary to use the array module with C code interface).