python - 使用没有停止值的 slice() 进行切片

Question

[:] 是否有使用 python 内置的 slice 类的等效项？

In [8]: 'abcdef'[:3]
Out[8]: 'abc'

In [9]: 'abcdef'[slice(3)]
Out[9]: 'abc'

In [10]: 'abcdef'[:]
Out[10]: 'abcdef'

In [11]: 'abcdef'[slice()]
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-11-9afb03fec62a> in <module>()
----> 1 'abcdef'[slice()]

TypeError: slice expected at least 1 arguments, got 0

Answer 1

可以使用None，默认:

>>> 'abcdef'[:]
'abcdef'
>>> 'abcdef'[None:]
'abcdef'
>>> 'abcdef'[None:None]
'abcdef'
>>> 'abcdef'[None:None:None]
'abcdef'
>>> 'abcdef'[slice(None)]
'abcdef'
>>> 'abcdef'[slice(None, None)]
'abcdef'
>>> 'abcdef'[slice(None, None, None)]
'abcdef'