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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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