Python学习笔记——切片操作

#slice[start:stop:step]

# 0 represent the left end of the sequence, -1 represents the right end of the sequence.

mystring = "my string"

#if the sign of the step is negative, then

#the default value of the start is -1, and the default value of the stop is zeor.

mystring[::-1] #'gnirts ym'

mystring[:3:-1] #'gnirt'

mystring[3::-1] #'s ym'

#if the sign of the step is positive, then

#the default value of the start is 0, and the defalut value of the stop is -1.

mystring[::1] #'my string'

mystring[:3:1] #'my '

mystring[3::1] #'string'

# start(0) ------- stop(-1), if the sign of the step is positive.

# stop(0) -------- start(-1), if the sign of the step is negative.