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10.5: List slices

  • Page ID
    40784
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    The slice operator also works on lists:

    >>> t = ['a', 'b', 'c', 'd', 'e', 'f']
    >>> t[1:3]
    ['b', 'c']
    >>> t[:4]
    ['a', 'b', 'c', 'd']
    >>> t[3:]
    ['d', 'e', 'f']
    

    If you omit the first index, the slice starts at the beginning. If you omit the second, the slice goes to the end. So if you omit both, the slice is a copy of the whole list.

    >>> t[:]
    ['a', 'b', 'c', 'd', 'e', 'f']
    

    Since lists are mutable, it is often useful to make a copy before performing operations that modify lists.

    A slice operator on the left side of an assignment can update multiple elements:

    >>> t = ['a', 'b', 'c', 'd', 'e', 'f']
    >>> t[1:3] = ['x', 'y']
    >>> t
    ['a', 'x', 'y', 'd', 'e', 'f']
    

    10.5: List slices is shared under a CC BY-NC 3.0 license and was authored, remixed, and/or curated by Allen B. Downey.

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