Array in Python | Set 1 (Introduction and Functions)

Other than some generic containers like lists, Python in its definition can also handle containers with specified data types. The array can be handled in python by a module named “array“. They can be useful when we have to manipulate only specific data type values.

Properties of Arrays

● Each element of the array is of the same data type and same size. For example: For an array of integers with the int data type, each element of the array will occupy 4 bytes. 

● Elements of the array are stored in contiguous memory locations.

Operations on Array :

1. array(data type, value list):- This function is used to create an array with data type and value list specified in its arguments. Some data types are mentioned in the table below.

Type Code	C Type	Python Type	Minimum size in Bytes
‘b’	signed char	int	1
‘B’	unsigned char	int	1
‘u’	Py_UNICODE	unicode character	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

2. append():- This function is used to add the value mentioned in its arguments at the end of the array.
3. insert(i,x) :- This function is used to add the value(x) at the ith position specified in its argument.

Python3

# Python code to demonstrate the working of
# array(), append(), insert()

# importing "array" for array operations
import array

# initializing array with array values
# initializes array with signed integers
arr = array.array('i', [1, 2, 3])

# printing original array
print ("The new created array is : ",end=" ")
for i in range (0, 3):
    print (arr[i], end=" ")

print("\r")

# using append() to insert new value at end
arr.append(4);

# printing appended array
print("The appended array is : ", end="")
for i in range (0, 4):
    print (arr[i], end=" ")

# using insert() to insert value at specific position
# inserts 5 at 2nd position
arr.insert(2, 5)

print("\r")

# printing array after insertion
print ("The array after insertion is : ", end="")
for i in range (0, 5):
    print (arr[i], end=" ")

Output

The new created array is :  1 2 3 
The appended array is : 1 2 3 4 
The array after insertion is : 1 2 5 3 4 

Output: 

The newly created array is: 1 2 3 
The appended array is: 1 2 3 4 
The array after insertion is: 1 2 5 3 4 

4. pop():- This function removes the element at the position mentioned in its argument and returns it.
5. remove():- This function is used to remove the first occurrence of the value mentioned in its arguments.

Python3

# Python code to demonstrate the working of
# pop() and remove()

# importing "array" for array operations
import array

# initializing array with array values
# initializes array with signed integers
arr= array.array('i',[1, 2, 3, 1, 5])

# printing original array
print ("The new created array is : ",end="")
for i in range (0,5):
    print (arr[i],end=" ")

print ("\r")

# using pop() to remove element at 2nd position
print ("The popped element is : ",end="")
print (arr.pop(2));

# printing array after popping
print ("The array after popping is : ",end="")
for i in range (0,4):
    print (arr[i],end=" ")

print("\r")

# using remove() to remove 1st occurrence of 1
arr.remove(1)

# printing array after removing
print ("The array after removing is : ",end="")
for i in range (0,3):
    print (arr[i],end=" ")

Output

The new created array is : 1 2 3 1 5 
The popped element is : 3
The array after popping is : 1 2 1 5 
The array after removing is : 2 1 5 

Output: 

The newly created array is: 1 2 3 1 5 
The popped element is: 3
The array after popping is: 1 2 1 5 
The array after removing is: 2 1 5 

6. index():- This function returns the index of the first occurrence of the value mentioned in the arguments.
7. reverse():- This function reverses the array.

Python3

# Python code to demonstrate the working of
# index() and reverse()

# importing "array" for array operations
import array

# initializing array with array values
# initializes array with signed integers
arr= array.array('i',[1, 2, 3, 1, 2, 5])

# printing original array
print ("The new created array is : ",end="")
for i in range (0,6):
    print (arr[i],end=" ")

print ("\r")

# using index() to print index of 1st occurrence of 2
print ("The index of 1st occurrence of 2 is : ",end="")
print (arr.index(2))

#using reverse() to reverse the array
arr.reverse()

# printing array after reversing
print ("The array after reversing is : ",end="")
for i in range (0,6):
    print (arr[i],end=" ")

Output

The new created array is : 1 2 3 1 2 5 
The index of 1st occurrence of 2 is : 1
The array after reversing is : 5 2 1 3 2 1 

Output: 

The newly created array is: 1 2 3 1 2 5 
The index of 1st occurrence of 2 is: 1
The array after reversing is: 5 2 1 3 2 1

Where can arrays be used?

● Arrays should be used where the number of elements to be stored is already known. 

● Arrays are commonly used in computer programs to organize data so that a related set of values can be easily sorted or searched. 

● Generally, when we require very fast access times, we usually prefer arrays since they provide O(1) access times. 

● Arrays work well when we have to organize data in multidimensional format. We can declare arrays of as many dimensions as we want. 

● If the index of the element to be modified is known beforehand, it can be efficiently modified using arrays due to quick access time and mutability.

Reference :
https://docs.python.org/3/library/array.html#module-array
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