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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!

kmario23
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FurtiveFelon
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7 Answers7

123

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]
Angela
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123

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

 start = 4
 end = None
 test[start:end]
recursive
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    Oh thank you! i was looking for this, but didn't know how to search for it :). I feel the accepted answer is sort of incomplete without this, because leaving an end index is trivial and has enough documentation. – Anubis May 05 '18 at 14:02
  • This same technique is also very useful to do the same thing with slice(4, None), where the colon approach does not work. – mightypile Mar 04 '23 at 19:17
18

Simply omit the end.

test[n:]
Matthew
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5

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

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

Return a slice of the list after a starting value:

my_list = ['a','b','c','d']
start_from = 'b' # value you want to start with
slice = my_list[my_list.index(start_from):] # returns slice from starting value to end
MarMat
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3

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)
kmario23
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1

What you are looking for is to use something like:

inputs = "ababbbaAab"
for i in range(n):
    print(i, inputs[:i] + inputs[i:i+1])

The output:

0 a
1 ab
2 aba
3 abab
4 ababb
5 ababbb
6 ababbba
7 ababbbaA
8 ababbbaAa
9 ababbbaAab

See that if i == 0

then inputs[:i] == [] and inputs[i:i+1] == a

and if i == len(inputs) - 1

then inputs[:i] == [ababbbaAa] and inputs[i:i+1] == b

Otieno Rowland
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