Arrays in Python | How Arrays and Lists Work in Python?

Introduction to Arrays in Python

Arrays is a collection of homogeneous items where each item has their own index value and index starts from 0. Python doesn’t have an built-in support for Arrays, but we can import array and use them. There is another datatype similar to arrays in Python i.e, Lists which are useful as arrays in Python but are different in a way that lists can hold any type of values but Arrays store only similar type of values, another lists are built-in datatype in Python whereas, Arrays you have to import from array module.

Index: is the number representing a value in array, and always start with 0.
element: is the value in an array.
len(): is the total count of elements in an array.
append(): This is the method to add an element to the array.
remove(): is the method to remove an element from the array.

There are many methods similar to append and remove to help us perform various operations on the array or lists. The for-in loop structure is used to loop through the array in Python. Let us learn this as well

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 the value at a particular index in an array we make use of a set of square brackets [ ], also we can use the for-in loop to iterate through the array. Array has indices (plural form of an index) and values. At each index, a value is stored. Why we use arrays is because it is difficult to store and remember hundred of numbers at a time, it would be simpler and easier to use arrays in that case, say the integer array is like the following. array (‘i’, [1, 2 , 3, 4 , 5, 6, 7, 8, 9,10] ) then to access these values we will use the following format.

a[0] => 1

a[1] => 2

a[2] => 3

a[3] => 4

a[4] => 5

a[5] => 6

a[6] => 7

a[7] => 8

a[8] => 9

a[9] => 10

Remember, the index starts at 0. We will use a for-in loop also to loop through the given array:

for i in a print a[i]

Which will give us the values from 1 to 10.

How to Create Arrays in Python?

To create an array in Python we need to import the array module first.

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import array as arr

where,

arr => is an alias

The other way to import the module is in the following manner:

from array import *

The syntax to create an array is:

array(typecode [,intializer])

where,

typecode => int or float or double or the type of value the array holds.

initializer => is the optional value and can be of any type like list, string, or any iterable elements of a particular type.

The typecode with its value is mentioned below in a tabular format.

TypeCode	C Type	Python Type	Value
i	signed int	int	2
I	Unsigned int	long	2
b	signed char	int	1
B	Unsigned char	int	1
h	signed short	int	2
H	Unsigned short	int	2
l	signed long	int	4
L	Unsigned long	int	4
f	float	float	8
d	double	float	4

Let us go through the following examples to understand each of these.

Typecode: i

Code:

import array as arr a=arr.array('i', [10 , 20 ,30] ) print("Element at 0th index: " , a[0]) print("Element at 1st index: " , a[1]) print("Element at 2nd index: " , a[2])

Output:

array.typecode()

This function returns the value of typecode used in the given array.

Code:

#importing array module import array as arr #creating array a1 = arr.array('i', [100,200,300] ) #printing array with method print(a1.typecode)

Output:

2. insert()

Syntax:

array.insert(index, element)

It adds an element to the array before the index

Code:

#importing array module import array as arr #creating array a = arr.array('i', [100,200,300]) #inserting a value of 400 to after index 2 a.insert(3, 400); #looping through array a for i in a: print(i)

Output:

3. update()

Syntax:

arrayname[index] = value

It updates a particular value at an index to the new value.

Code:

#importing array module import array as arr #creating array a = arr.array('i', [100,200,300] ) #updating a value of 200 to 400 a[1] = 400 #looping through array a for i in a: print(i)

Output:

4. delete()

Syntax:

array.remove(element)

This function removes the element from the array.

Code:

#importing array module import array as arr #creating array a = arr.array('i', [100,200,300] ) #deleting a value 100 a.remove(100) #looping through array a for i in a: print(i)

Output:

5. append()

Syntax:

array.append(element)

This function appends the element to the end of the array.

Code :

#importing array module import array as arr #creating array a = arr.array('i', [100,200,300] ) #appending 400 to the end a.append(400) #printing array for i in a: print(i)

Output:

6. reverse()

Syntax :

array.reverse()

This function reverses the order of elements in the given array.

Code:

#importing array module import array as arr #creating array a = arr.array('i', [100,200,300] ) //applying the reverse method to the array a.reverse() //printing the array for i in a: print(i)

Output:

7. count()

Syntax:

array.count(element)

This function returns how many times the element occurred in the given array.

Code:

#importing array module import array as arr #creating array a3 = arr.array('i', [100,200,300,100,400,100,500] ) #printing the array count print(a3.count(100))

Output:

8. index()

Syntax:

array.index(x)

This method returns “i” which is the index and the smallest value of the first occurrence of x in the array.

Code:

#importing array module import array as arr #creating array a3 = arr.array('i', [700,200,300,100,400,100,500] ) #search the value 100 and return its index print(a3.index(100))

Output:

9. pop()

Syntax:

array.pop([ i ])

This function removes and returns the element that has index i of the given array. By default, it removes and returns the last element.

Code:

#importing array module import array as arr #creating array a3 = arr.array('i', [100,200,300] ) # removing 100 and printing print(a3.pop(0))

Output:

pop()

10. itemsize()

Syntax:

array.itemsize()

Code:

#importing array module import array as arr #creating array a3 = arr.array('i', [100,200,300] ) #printing the itemsize print(a3.itemsize)

Output:

11. len() method

Syntax:

len(arrayname)

This method gives the array length.

Code:

#importing array module import array as arr #creating array a3 = arr.array('i', [100,200,300,400,500] ) #printing the length of method print(len(a3))

Output:

Conclusion

Hope this article is informative for all of your concepts and also hope this article is interesting enough to encourage you to learn new things. Practice will only lead you to perfection so practice as much as possible.

Introduction to Arrays in Python

How does Array Work in Python?

How to Create Arrays in Python?

Typecode: i

Typecode: I

Typecode: b

Typecode: B

Typecode: h

Typecode: l

Typecode: L

Typecode: f

Typecode: d

Array Methods in Python

1. typecode()

2. insert()

3. update()

4. delete()

5. append()

6. reverse()

7. count()

8. index()

9. pop()

10. itemsize()

11. len() method

Conclusion

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