What does python step size mean?

In Python sequences (lists and tuples are both sequences), you can use slicing operations: sequence[start : end : step] The first two are easy to understand, they are the position of the start index and the position of the end index. (Python provides two indexes: 0 from left to right... index-1 and -1 from right to left... -index). The key is the meaning of this step.

Let me introduce to you the meaning of step (step length):

>>>s = ‘abcdefgh’  
>>>s[::-1]   
 ’hgfedcba’  
>>>s[::2]   
 ’aceg’

>>>s = 'abcdefgh'
>>>s[::-1]
 'hgfedcba'
>>>s[::2] 
 'aceg'

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Actually, step here represents the step size of the slice (step cannot be 0, the default is 1):

If step > 0, it means from left to right Make slices. At this time, start must be less than end to have a result, otherwise it will be empty. For example: the result of s[0,: 5: 2] is 'ace'

If step

Then, s[::-1] means slicing from right to left with a step size of 1; s[: :2] means slicing from left to right with a step size of 2

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