Examples of how to slice a list in python:
Create a list in python
Lets first create a list in python
mylist = ['a','b','c','d','e','f','g','h','i']
To get an element stored in a list using its indexe:
mylist[0]
returns
'a'
and
mylist[4]
returns
'e'
Get number of elements in a list
To get the size of a list in python, a solution is to use the built-in function len()
s = len(mylist)print(s)
returns here
9
Get first n elements of a list in python
To get first n elements of a list in python a solution is to do mylist[-n:]. Example, extract only the first 3 elements:
mylist[:3]
returns
['a', 'b', 'c']
same as
mylist[0:3]
also returns
['a', 'b', 'c']
Get last n elements of a list in python
To get last n elements of a list in python a solution is to do mylist[-n:]. Example, extract only the last 2 elements:
mylist[-2:]
returns
['h', 'i']
Note: same as doing:
mylist[s-2:s]
also returns
['h', 'i']
Get elements between indexes m,n
To get elements between indexes m,n, a solution is to do mylist[m:n]. Example:
mylist[2:5]
returns
['c', 'd', 'e']
Get every nth element in a list
To get for example every 2 element in a list
mylist[::2]
returns
['a', 'c', 'e', 'g', 'i']
Another example
mylist[::3]
returns
['a', 'd', 'g']
Get every nth element in a list, between indexes m1,m2
To get every nth element in list, between indexes m1,m2, a solution is to do mylist[m1:m2:n]. Example:
mylist[0:4:2]
returns
['a', 'c']
