Python slice numpy arrays

Slicing refers to extracting a range of elements from the array. The format of slicing operation is given here:

arrayname[start:stop:stepsize]

The default value for 'start' is 0, for 'stop' is n-1 (n is number of elements) and for 'stepsize' is 1. Counting starts from 0th position. For example, if we write:

a = [10, 11, 12, 13, 14, 15]

a[1:6:2]

Suppose, we write a[:] or a[::] without specifying anything for start, stop and stepsize, it will extract from 0th element till the end of the array. So, all elements are extracted. Suppose, we write a[2:] , it starts at 2nd element and ends at last element.

slice numpy arrays examples:

What will be the output of the following program

from numpy import * 
a = [10, 11, 12, 13, 14, 15]
print(a[-1:4:-1])

Python program to understand slicing operations on arrays.

from numpy import *
a = arange(10, 16) 
print(a)
b = a[1:6:2] 
print(b) 
b = a[::] 
print(b) 
b = a[-2:2:-1] 
print(b) 
b = a[:-2:] 
print(b)

Python program to retrieve and display elements of a numpy array using indexing.

from numpy import * 
a = arange(10, 16) 
print(a) 
a = a[1:6:2] 
print(a) 
i=0
while(i<len(a)):
print(a[i]) 
i+=1