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Array Operations

Array

1.Retrieve element

for Retrieving elements from an array, there are two different ways

  1. Single element Retrieval
  2. Multiple elements retrieval using slicing.

1. Single Element Retrieval

  • A collection of elements each identified by an array index.
  • Index start at zero(0) array.Because of the index, random access of elements is possible.
  • Use [] parenthesis to retrieve an element from an array
  • Array elements can be accessed using positive index start from the first element in the array
like 0,1,2,3,4...
  • Array elements also can be accessed using negative indexes which start from ending of the list
like -1,-2,-3,-4..

Syntax:

array_name[index]

Example:

import array

data=array.array("i",[20,10,15,23])

#for 20 use 0 index to get value from it
result=data[0]
print("Element At 0 Index")
print(result)
#Result:20

#Access 20 using negative index
result=data[-4]
print("\nGet 20 Element Using Negative Index")
print(result)
#Result:20


#for 15 use 2 index to get value from it
result=data[2]
print("\nElement At 2nd Index")
print(result)
#Result:15

#for 15 using Negative index
result=data[-2]
print("\nGet element At -2 Index")
print(result)
#Result:15

#For outer index 
result=data[10]
print(result)
#Result Error: array index out of range

Output:

Element At 0 Index
20

Get 20 Element Using Negative Index
20

Element At 2nd Index
15

Get element At -2 Index
15
Traceback (most recent call last):
  File "/tmp/sessions/8796c948b36129d7/main.py", line 31, in <module>
    result=data[10]
IndexError: array index out of range

2.Multiple Elements using slicing

  • In Python, we can easily access a range of items in an array using the slicing operator :

Normal Syntax:

array_name[startindex(including):EndIndex(Excluding)]

Other Syntax :

array_Name[:]              > All Elements
array_name[start:end]    > Begining to End
array_name[:end]        > Begining to end
array_name[start:]      > begining to end

Examples:

import array

data=array.array("i",[20,10,15,23])

#ALL Elements
start=0
end=4

result=data[start:end]
print("Array From 0 index to till 4 index")
print(result)
#Result:array('i', [20, 10, 15, 23])

#Get First 2 Elements
result=data[:2] #or data[0:2]
print("\nGet First 2 Element")
print(result)
#Result:array('i', [20, 10])

#Get Last 3 Elements
result=data[1:] #or data[1:3]
print("\nGet Last 3 Element")
print(result)
#Result:array('i', [10, 15, 23])

Output:

Array From 0 index to till 4 index
array('i', [20, 10, 15, 23])

Get First 2 Element
array('i', [20, 10])

Get Last 3 Element
array('i', [10, 15, 23])

2.Add Element

  • After the creation of the array, we can add another element to array with the help of following built-in functions
1. append()
2. insert()
3. extend()

1.append()

  • append() function add a single element to an array at the end of the array

Syntax:

arrayName.append("element")

Example:

import array

data=array.array("i",[20,10,15,23])
print("Before append of new Element")
print(data)


#Append 6 to the data array
data.append(6)
print("After appending element")
print(data)

Output:

Before append of new Element
array('i', [20, 10, 15, 23])

After appending element
array('i', [20, 10, 15, 23, 6])

2.insert()

  • append() add elements at only end of the array but if you want to add an element at the specific position then use insert.
  • if an element is already present at insertion position then element at insertion position will be shifted to the right side by one.
  • If you pass out of range positive index then element should be added at the end of an array.
  • If you pass out of range negative index then element should be added at the beginning of an array.

Syntax:

array_name.insert(index,"value")

Example:

import array

data=array.array("i",[20,10,15,23])
print("Normal Array")
print(data)


#Append 6 at 1th position
data.insert(1,6)
print("After inserting 6  at first position element")
print(data)

Output:

Normal Array
array('i', [20, 10, 15, 23])'


After inserting 6  at first position element
array('i', [20, 6, 10, 15, 23])

3.extend()

  • append() and insert() function add single element to an array to add multiple element to an array or join two different array extend() built in function is is used
  • Add several items using extend() method.
  • extend() appends iterating to the end of the array

Syntax:

array_name.extend(iterable_object)

iterable_object:list,tuple

Example:

import array

data=array.array("i",[20,10,15,23])
print("Normal Array")
print(data)


#add  [6,11,12] array to data array
data.extend([6,11,12])

print("\n\n Array After Extending [6,11,12] ")
print(data)

Output:

Normal Array
array('i', [20, 10, 15, 23])

Array After Extending [6,11,12] 
array('i', [20, 10, 15, 23, 6, 11, 12])

3.Update Element

  • The array is the mutable object. so elements of an array are changeable

Syntax:

To change or modify an element of an array use index of that element

array_name[index]=value

To modify some range of elements from an array

array_name[startindex:endindex]=value

Example:

import array

data=array.array("i",[20,10,15,23])
print("Normal Array")
print(data)

#update 20 with 30 and 20 element at 0 index
data[0]=30
print("\nArray after modification of 20 with 30")
print(data)

#Update last 2 element 9 and 12
data[-2:]=array.array('i',[9,12])
print("\nArray After updating multiple values")
print(data)

Output:

Normal Array
array('i', [20, 10, 15, 23])

Array after modification of 20 with 30
array('i', [30, 10, 15, 23])

Array After updating multiple values
array('i', [30, 10, 9, 12])

data[0]='h'
This will generate error
Erro:an integer is required (got type str)


data[552]='1'
Error:array assignment index out of range

4. Remove Element

  • You can delete a complete array or element there are the following options are available.
1. del
2. pop()
3. remove()

1.del

  • We can delete one or more items using python del statement.
  • we can also delete a complete array using del keyword.

Syntax:

delete of specific index item

del array_name[index]

Delete Complete array

del array_name

Examples:

import array

data=array.array("i",[20,10,15,23])
print("Normal Array")
print(data)

#Delete the first Element from an array
del data[0]

print("\nAfter delete first element")
print(data)

#delete complete array
del data

print("\nErrror")
print(data)
#result:name 'data' is not defined

Output:

Normal Array
array('i', [20, 10, 15, 23])

After delete first element
array('i', [10, 15, 23])

Errror
Traceback (most recent call last):
  File "/tmp/sessions/139fbf48debb94d3/main.py", line 17, in <module>
    print(data)
NameError: name 'data' is not defined

2.pop()

  • pop() method used to remove an item at the given index.
  • pop() also return an item which is deleted

Syntax:

array_name.pop(index)

Example:

import array

#Normal Array
arr=array.array('i',[20, 10, 15, 23])

#print Normal Array
print("Normal Array")
print(arr)

#Delete last Element
arr.pop()

print("\nAfter Poping Last Element")

#print array after pop
print(arr)

Output:

Normal Array
array('i', [20, 10, 15, 23])

After Poping Last Element
array('i', [20, 10, 15])

3.remove()

  • We can use the remove() method to remove the given item.
  • remove() method accept element instead of the index.
  • remove() method removes an element from an array and doesn't return anything
  • If the element not found in list remove() gives an error
x not in the list

Syntax:

array_name.remove(elements)

Example:

import array

data=array.array("i",[20,10,15,23])
print("Normal Array")
print(data)

#Remove 10 from an array using remove()
data.remove(10)


print("\nPrint array after remove of 10")
print(data)

Output:

Normal Array
array('i', [20, 10, 15, 23])

Print array after remove of 10
array('i', [20, 15, 23])