Array in Python
An Array is a collection of similar data items stored in contiguously on memory.
We can use List as array.
The difference between the array and List is, we can not restrict List to store the type of element.
for example :
a = [1, 2.5, 'Python']
As we can see in list there may be any type's element.
In python, we can create array by using array
module.
Creating an Array :
Array in python can be created by importing array
module.
import array as ar
Once we have imported the array
module, we can declare an array. Here is how we do it:
arrayName = array(typecode, [Initializers])
In the above declaration, 'typecode' lets python know the type of array and 'Initializers' are the values with which array is initialized.
for example :
import array as ar myArray = ar.array('i',[1, 2, 3, 4, 5])
In the example above, typecode used is 'i'. This typecode represents signed integer whose size is 2 bytes.
Commonly used type codes are :
Type Code | Represents | Python Type | Size in Bytes |
---|---|---|---|
'b' | signed char | int | 1 |
'B' | unsigned char | int | 1 |
'u' | unicode character | Unicode Character | 2 |
'h' | signed short | int | 2 |
'H' | unsigned short | int | 2 |
'i' | signed integer | int | 2 |
'I' | unsigned integer | 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 |
Since List and array are related to each other in terms of operation, you should know how to use Python List .
1. Creation of array with 5 elements
>>> import array as ar >>> myArray = ar.array('i',[1, 2, 3, 4, 5])
2. Access array elements :
We use indices to access array elements.It also support negative index.
>>> print(myArray[0]) 1 >>> print(myArray[3]) 4 >>> print("Last Element",myArray[-1]) Last Element 5
3. Slicing an array :
It is similar to list.
>>> print(myArray[:]) array('i', [1, 2, 3, 4, 5]) >>> print(myArray[1:4]) array('i', [2, 3, 4])
4. Append a new element :
>>> myArray.append(20) >>> print(myArray) array('i', [1, 2, 3, 4, 5, 20])
5. Insert a new value :
>>> myArray.insert(0,10) >>> print(myArray) array('i', [10, 1, 2, 3, 4, 5, 20])
6. Extend array :
>>> new_array = ar.array('i',[10,20,30,40]) >>> myArray.extend(new_array) >>> print(myArray) array('i', [10, 1, 2, 3, 4, 5, 20, 10, 20, 30, 40]) >>>
7. Add items from List to array :
>>> myArray = ar.array('i',[1,2,3,4,5]) >>> myList = [10,20,30,40,50] >>> myArray.fromlist(myList) >>> print(myArray) array('i', [1, 2, 3, 4, 5, 10, 20, 30, 40, 50])
8. Remove an array element :
>>> myArray = ar.array('i',[1,2,3,4,5]) >>> myArray.remove(3) >>> print(myArray) array('i', [1, 2, 4, 5]) >>>
9. Pop an element from array :
>>> myArray = ar.array('i',[1,2,3,4,5]) >>> myArray.pop() 5 >>>
10. Get the element's index :
>>> myArray = ar.array('i',[1,2,3,4,5]) >>> myArray.index(4) 3 >>> myArray.index(5) 4 >>>
11. Reverse an array :
>>> myArray = ar.array('i',[1,2,3,4,5]) >>> myArray.reverse() >>> print(myArray) array('i', [5, 4, 3, 2, 1]) >>>
12. Get the occurrence of an element :
>>> myArray = ar.array('i',[1,1,1,2,3,4,5]) >>> myArray.count(1) 3 >>>
13. Convert array to a List :
>>> myArray = ar.array('i',[1,1,1,2,3,4,5]) >>> myList = myArray.tolist() >>> print(myList) [1, 1, 1, 2, 3, 4, 5] >>>
Next chapter is Python Functions
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