How to slice a list from an element n to the end in python?
Question:
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!
Answers:
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]
Simply omit the end.
test[n:]
If you’re using a variable as the range endpoint, you can use None.
start = 4
end = None
test[start:end]
Leaving out the end still works when you want to skip some:
range(10)[3::2] => [3, 5, 7, 9]
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
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)
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
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!
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]
Simply omit the end.
test[n:]
If you’re using a variable as the range endpoint, you can use None.
start = 4
end = None
test[start:end]
Leaving out the end still works when you want to skip some:
range(10)[3::2] => [3, 5, 7, 9]
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
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)
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