Slicing and truncating sequences in python

Sequence concept

In the sharding rules, list, tuple, and str (string) can all be called sequences, and they can all be sliced ​​according to the rules

Slicing operation

Note that the subscript 0 of the slice represents the first element in sequence, -1 represents the first element in reverse order; and the slice does not include the right boundary , for example [0:3] represents elements 0, 1, 2 excluding 3.

l=['a','b','c','d',5]

1. Get the first 3 elements of the list

>>> l[0:3]
['a', 'b', 'c']
>>> l[:3]
['a', 'b', 'c']

2. Get the last 3 elements of the list

>>> l[-3:]
['c', 'd', 5]

Since the list does not include the right boundary, So just take the right boundary of the last three elements and leave it unspecified.

3. Get all elements

>>> l[:]
['a', 'b', 'c', 'd', 5]
>>> l[0:]
['a', 'b', 'c', 'd', 5]

4.Specify the growth step

>>> L=list(range(100))
>>> L[0:101:10]
[0, 10, 20, 30, 40, 50, 60, 70, 80, 90]

Specify 10 steps as the unit

Other slices

#!/usr/bin/env python3
#-*- coding:utf-8 -*-
vlist=['a','b','c']
vtuple=('a','b','c')
vstr='abc'
print (vlist[0:2]);
print (vtuple[0:2]);
print (vstr[0:2])

The output result is:

======================== RESTART: C:/Python35/list.py ========================
['a', 'b']
('a', 'b')
ab

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