How to slice a list from an element n to the end i

问题:

I'm having some trouble figuring out how to slice python lists, it is illustrated as follows:

>>> test = range(10)
>>> test
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> test[3:-1]
[3, 4, 5, 6, 7, 8]
>>> test[3:0]
[]
>>> test[3:1]
[]
>>> test
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

To my understanding, python slice means lst[start:end], and including start, excluding end. So how would i go about finding the "rest" of a list starting from an element n?

Thanks a lot for all your help!

回答1:

You can leave one end of the slice open by not specifying the value.

test[3:] = [3, 4, 5, 6, 7, 8, 9]
test[:3] = [0, 1, 2]

回答2:

If you're using a variable as the range endpoint, you can use None.

 start = 4
 end = None
 test[start:end]

回答3:

Simply omit the end.

test[n:]

回答4:

Leaving out the end still works when you want to skip some:

range(10)[3::2] => [3, 5, 7, 9]

回答5:

Return a slice of the list after a starting value:

list = ['a','b','c','d']
start_from = 'b' # value you want to start with
slice = list[list.index(start_from):] # returns slice from starting value to end

回答6:

You can also use the None keyword for the end parameter when slicing. This would also return the elements till the end of the list (or any sequence such as tuple, string, etc.)

# for list
In [20]: list_ = list(range(10))    
In [21]: list_[3:None]
Out[21]: [3, 4, 5, 6, 7, 8, 9]

# for string
In [22]: string = 'mario'
In [23]: string[2:None]
Out[23]: 'rio'

# for tuple
In [24]: tuple_ = ('Rose', 'red', 'orange', 'pink', 23, [23, 'number'], 12.0)
In [25]: tuple_[3:None]
Out[25]: ('pink', 23, [23, 'number'], 12.0)