python extract variable from a list

Question

I'm pretty new to python and I'm stacked on a simple problem: i have a list:

mylist = [1, 2, 3, 4]

if I extract one element like this:

print(my_list[1:2])

I get a list of one element, but i cannot compute any calculus by treating it as a variable :

print(my_list[1:2]+1)

because i get the error:

Traceback (most recent call last): File "C:\...\test_tuple.py", line XX, in <module> print(my_list[1:2]+1) TypeError: can only concatenate list (not "int") to list

how do I convert this single element list to a variable?

since you are doing slicing you are getting another list as a result, if you want to obtain the first variable from that list, you need to do something like this, print(my_list[1:2][0]+1) — Ishan Sahu
– Ishan Sahu, Commented Sep 9, 2022 at 12:46

Rik · Accepted Answer · 2023-05-01 15:10:07Z

3

What you are doing, with :, is slicing. This means grabbing a piece of a list as a new list. What you want is just one index, which you can do be using:

mylist = [1, 2, 3, 4]
print(mylist[2]+1)

You can also turn a one element list into a variable by using:

mylist = [1, 2, 3, 4]
new_list = mylist[1:2]
print(new_list[0]+1)

Lastly you can also use numpy arrays on which you can perform calculations as if it were a normal number as follows:

import numpy as np

mylist = [1, 2, 3, 4]
new_arr = np.array(mylist[1:2])
print(new_arr+1)

of course the first solution is the best in this case, but sometimes other solutions can fit your problem better.

edited May 1, 2023 at 15:10

answered Sep 9, 2022 at 12:32

Rik

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Comments

R. Baraiya · Accepted Answer · 2022-09-09 12:39:35Z

0

You're error is about, you are adding number to [],

you need to add number to number like below code;

print(my_list[1:2+1])

print(my_list[2+1])

print(my_list[2]+1) ##here youre adding to the value like (my_list[2])3+1 that it will not give you error

edited Sep 9, 2022 at 12:39

answered Sep 9, 2022 at 12:34

R. Baraiya

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