“不会slice,绝不能说会python”,slice的重要性不言而喻。

Basis

  • index start with 0
  • support negtive index
  • [included:excluded:step] eg: [:], [::-1]
  • work with list, tuple and string

step

Ipython 中的示例
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In [1]: e = range(6)
In [2]: e
Out[2]: [0, 1, 2, 3, 4, 5]
In [3]: e[:]
Out[3]: [0, 1, 2, 3, 4, 5]
In [4]: e[6]
IndexError
In [5]: e[5]
Out[5]: 5
In [6]: e[:5]
Out[6]: [0, 1, 2, 3, 4]
In [7]: e[:6]
Out[7]: [0, 1, 2, 3, 4, 5]
In [8]: e[::-1]
Out[8]: [5, 4, 3, 2, 1, 0]
In [9]: e[6:0]
Out[9]: []
In [10]: e[6:0:-1]
Out[10]: [5, 4, 3, 2, 1]
In [11]: 0 in e[6:0:-1]
Out[11]: False
In [12]: e[5:0:-1]
Out[12]: [5, 4, 3, 2, 1]
In [13]: e[5:0:-1] == e[6:0:-1]
Out[13]: True
In [14]: e[-1:-7:-1]
Out[14]: [5, 4, 3, 2, 1, 0]
In [15]: e[-1:-7:-1] == e[::-1]
Out[15]: True
In [16]: e[-1:-9:-1]
Out[16]: [5, 4, 3, 2, 1, 0]
In [17]: e[::-2] == e[-1:-7:-2]
Out[17]: True
In [18]: e[::-2] == e[-1:-8:-2]
Out[18]: 'Just do IT'
  • e[::-1] == e[-1:-7:-1]
  • slice切片中索引可以超出实际范围
  • 带有步长的切片,索引顺序和步长方向一致
  • 切片总是新产生一个对象,而不是改变原有对象

总结

Just do IT