Python Arrays | Python Array Module

Array is yet another interesting topic of python, which covers and requires a good knowledge of basics before actually applying it. But the article is of course, one more magic spell from fairy basket, so why would it be partial to any coder?

This article takes you from basic to advanced knowledge of Python array modules. So, let’s get started. 

What is Array Module in Python?

The array module defines an object type that can compactly represent an array of some basic values as characters, integers, floating-point numbers.

Arrays are sequence types and behave similarly as lists, except that the type of objects stored in them is constrained.
The module defines the following type:

class array.array(typecode[, initializer]): A new array whose items are restricted by the typecode, and initialized from the optional initializer value, which must be a list, a bytes-like object, or iterable over elements of the appropriate type.

Here’s a list of such type codes-

Type Code	C Type	Python Type	Minimum size (bytes)
b	signed char	int	1
B	unsigned char	int	1
u	Py_UNICODE	Unicode character; deprecated since Python 3.3	2
h	signed short	int	2
H	unsigned short	int	2
i	signed int	int	2
I	unsigned int	int	2
l	signed long	int	4
L	unsigned long	int	4
q	signed long long	int	8
Q	unsigned long long	int	8
f	float	float	4
d	double	float	8

How to Import Python Arrays?

syntax

>>> import array

Indexing an Array in Python

>>>
array=[5,9,5,9]

print(array[1])

Output

Python Array Class – Data Items

The class array has the following data items-

1. Array.typecodes: A string with all type codes.

2. Array.typecode: The typecode character used in creating the array.

3. Array.itemsize: The length of array 

>>>arr.itemsize

4. array.append(x): Append new item with value x to the end of the array.

>>>arr.append

5. array.append(x): Append new item with value x to the end of the array.

6. array.pop([i]):removes the element  “i”which is parsed.

>>>arr.pop

7. array.remove(x): Removes the first occurrence of x from the array.

>>>arr.remove

8. array.reverse(): Reverses the order of the items in the array.

>>>arr.reverse

9. array.index(x): Returns the smallest i such that i is the index of the first occurrence of x in the array.

>>>arr.index

10. array.insert(i, x): Inserts a new item with value x in the array before position i.

>>>arr.insert

11. array.buffer_info()

This returns a tuple that holds the address in memory and the length of elements in the buffer that holds the contents of the array in the runtime.

>>> arr.buffer

12. array.byteswap()

This performs an operation of bytes wap on an array in the runtime.

>>> arr.byte

13. array.count(x)

 finds out how many 3s there are in our Python array in the runtime.

>>> arr.count

14. array.extend(iterable)

This attaches the iterable to the end of the array in Python in the runtime.

>>> arr.extend

15. array.fromlist(list)

This appends item from a list to the Python arrays in the runtime.

>>> arr.fromlist

16. array.fromunicode(s)

This appends the Unicode string in the runtime

>>> arr.unicode

17. array.index(x)

This returns the index for the first occurrence of x in the runtime.

>>> arr.index

18. array.tobytes()

returns a representation in bytes of the values of the array in the runtime

>>> arr.tobytes()

19. array.tolist()

converts the array into a list in the runtime.

>>> arr.tolist()

 20. array.tounicode()

converts an array to a Unicode string in the runtime. 

>>> arr.tounicode

How does Array Work in Python?

The array is stored in contiguous memory locations, where the index is a sequence of numbers that represents the values stored at every particular index.

To access or refer to the value at a particular index in an array we make use of a set of square brackets [ ],(as in lists) also we can use the for-in loop to iterate through the array. The array has indices and values.

Array Module Example in python

import array as arr
a=arr.array('I', [10 , 20 ,50] )
print("Element at 0th index: " , a[0])
print("Element at 1st  index: " , a[1])
print("Element at 2nd index: " , a[2])

Output

Python Array Representation

Arrays can be declared in various ways and in different languages. The important points that should be considered are as follows:

• Index always starts with 0.
• We can access each element using its index.
• The length of the array defines the capacity to store the elements.

Python Array Operations

Some of the basic operations supported by an array are:

• Traverse – It prints all elements one by one.
• Insertion – It adds an element at a given index.
• Deletion – It deletes elements at the given index.
• Search – It searches the element using the given index or by the value.
• Update – It updates elements at the given index.

Searching Element in Python Array Example:

from array import *
array_techvidvan = array(‘i’, [0,1,2,3,4,5])
print (array_techvidvan.index(3))

Output:

Example of Traversing Array in Python

from array import *
array_TechVidvan = [0,1,2,3,4,5]
for x in array_TechVidvan:
 print (x)

Output:

Creating Python Arrays

for creating an array of numeric values, the coder needs to import the array module in runtime.

Example to Create Array in Python

import array as arr
p = arr.array('q', [1,5])
print(p)

Output:

Accessing Python Array Elements

Example to access Python Array Elements:

import array as arr
p = arr.array('j', [2,  80])
print("First element of list:", p[0])
print("Second element of list:", p[1])

Output:

Changing and Adding Elements in Python Array

Arrays are mutable therefore their elements can be changed in a similar way as lists in the code.

Code

import array as arr
numb = arr.array('k', [1, 109])
numb[0] = 0    
print(numb)     

Output:

adding elements in array

extend(): it appends iterable to the end of the array in any code.

Code

numb.extend([5])
print(numb)  

Output:

Removing Python Array Elements

Code

import array as arr
numb = arr.array('k', [1, 2,3 ])
del numb[2]  
print(numb) 

Output:

Code

del numb 
print(numb)

Output:

Searching an element in an Array

Code

import array 
   
arr = array.array('k', [1, 2])  
  
print ("The new created array is : ", end ="") 
for k in range (0, 2): 
    print (arr[k], end =" ") 

Output:

Updating Elements in an Array

Code

import array
print ("Array before", end =" ")
for k in range (0,2):
    print ([k], end =" ")

Output:

Looping Array Elements in Python

Code

list=[1,0]
for i in list:
  print(i)

Output:

Calculating Length of an Array in Python

Code

l=[1,0]
i = len(l)
print(i)

Output:

Slicing Arrays in Python

By using the slicing operator (:), it’s possible to access a range of elements present in the array in Python programming language. The following code snippet demonstrates using the slicing operator with an array :

Code

number_list = [2, 4, 22, 25, 24, 52, 46,10]
for i in range(1,5):
    print(i)
for j in range(5,8):
    print(j)

Output:

Arrays are mutable. Hence, their elements can be changed similarly as lists.The append() method is used for adding one element to an array while extend() method allows adding multiple elements. These new elements are added at the end of the array.

Although knowing how to deal with arrays isn’t a compulsory part of learning Python, being able to do so is surely an added advantage.Typically, the array module is generally  required for interfacing with C code. 

Python Lists Vs Arrays

Code

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

Output:

Summary

At the end of the article, we got an idea of how an array is similar to a list in many aspects, but surely there is a difference. The array is not very much recommended in Python as stated earlier but knowing it will add to your knowledge.

A good coder is someone who knows every aspect of code, and practice is a definite key. Try and check out array() yourself. Happy Pythonning!