It's possible to slice a python list like this:
>>> list=['a', 'b']
>>> list[0:1]
['a']
However, when passing the index as a string, an error is thrown:
>>> index="0:1"
>>> list[index]
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: list indices must be integers, not str
How can I specify a list index as a string? What data type is 0:1 in list[0:1], really?
n:m is syntactic sugar for a slice. You could split your index string, convert its parts to integers, and create a slice from those.
>>> lst = list(range(10))
>>> index = "1:4"
>>> s = slice(*map(int, index.split(':')))
>>> lst[s]
[1, 2, 3]
Works just the same with three parts:
>>> index = "1:9:2"
>>> s = slice(*map(int, index.split(':')))
>>> lst[s]
[1, 3, 5, 7]
If you want to allow for "blank" parts, the conversion gets a little bit more involved:
>>> index = "::-1"
>>> s = slice(*[int(x) if x else None for x in index.split(':')])
>>> lst[s]
[9, 8, 7, 6, 5, 4, 3, 2, 1, 0]
range will produce a range and not a list in Python3, correct me if I'm wrong?
list so it works with both.Why not just convert your slicing string into integers by splitting on :, and then using them as slicing indices.
list=['a', 'b']
slicer_str = '0:1'
slicer_int = [int(i) for i in slicer_str.split(':')]
print(list[slicer_int[0]:slicer_int[1]])
You can use exec() for this.
l = ['a', 'b']
index="0:1"
exec('print(l[{}])'.format(index))
The print is needed only to see the output. You can assign it to a variable and call the variable afterwards instead.
print, i.e. to assign the result to some variable, you should use eval instead of exec. Also, never use eval (or exec) if it can be helped.
exec('a = l[{}]'.format(index)) would assign to a as wellUse the [ : ] where you specify the start point and end point ,so you can easily trace what you intend to slice
