python slicing array code example

Example 1: python slice an array

a[start:stop]  # items start through stop-1
a[start:]      # items start through the rest of the array
a[:stop]       # items from the beginning through stop-1
a[:]           # a copy of the whole array
Example:
>>> a = [1, 2, 3, 4, 5, 6, 7, 8]
>>> a[1:4]
[2, 3, 4]

Example 2: slicing in python list

a = [1,2,3,4,5]
a[m:n] # elements grrater than equal to m and less than n
a[1:3] = [2,3]

Example 3: array slicing python

#slicing arrays:
#generic sampling is done by 
#arr[start:end] -> where start is the starting index and end is ending idx
>>> import numpy as np
>>> arr = np.array([1,2,3,4,5])
>>> print(arr[1:5]) #starting idx 1 to ending index 4
[2 3 4 5]#it will print from starting idx to ending idx-1

#if you leave the ending index blank it will print all 
#from the starting index till end
>>> arr = np.array([2,6,1,7,5])
>>> print(arr[3:])
[7 5]
>>> print(arr[:3]) #if you leave the starting index blank it will print from 0 index to the ending idx-1\
[2 6 1]
>>> print(arr[:])
[2 6 1 7 5]
#leaving both the index open will print the entire array.

##########STEP slicing########
#if you want to traverse by taking steps more than 1 
#we use step slicing in that case
#syntax for step slicing is : arr[start:end:step]
>>> arr = np.array([2,6,1,7,5,10,43,21,100,29])
>>> print(arr[1:8:2])#we have taken steps of two
[ 6  7 10 21]