[::- 'ollehreversing items with negative stridethe meanings of the first two bounds are essentially reversed that isthe slice [ : :- fetches the items from to in reverse order (the result contains items from offsets and ) 'abcedfgs[ : :- 'fdecbounds roles differ skipping and reversing like this are the most common use cases for three-limit slicesbut see python' standard library manual for more details (or run few experiments interactivelywe'll revisit three-limit slices again later in this bookin conjunction with the for loop statement later in the bookwe'll also learn that slicing is equivalent to indexing with slice objecta finding of importance to class writers seeking to support both operations'spam'[ : 'pa'spam'[slice( )'pa'spam'[::- 'maps'spam'[slice(nonenone- )'mapsslicing syntax slice objects with index syntax object why you will careslices throughout this booki will include common use-case sidebars (such as this oneto give you peek at how some of the language features being introduced are typically used in real programs because you won' be able to make much sense of realistic use cases until you've seen more of the python picturethese sidebars necessarily contain many references to topics not introduced yetat mostyou should consider them previews of ways that you may find these abstract language concepts useful for common programming tasks for instanceyou'll see later that the argument words listed on system command line used to launch python program are made available in the argv attribute of the builtin sys modulefile echo py import sys print(sys argvpython echo py - - - ['echo py''- ''- ''- 'usuallyyou're only interested in inspecting the arguments that follow the program name this leads to typical application of slicesa single slice expression can be used to return all but the first item of list heresys argv[ :returns the desired list string fundamentals