Slicing the second last character

Question

I have this string here '[2,3,1,1,]'

Im new to slicing and I only know how to slice from the start and from the end but not somewhere between, not even sure if that is possible.

could someone tell me how I can slice this '[2,3,1,1,]' to this '[2,3,1,1]' So removing the second last character only.

See also: https://stackoverflow.com/questions/38066836/python-best-way-to-remove-char-from-string-by-index — Chris, Sep 03 '22 at 15:34

Rahul K P · Accepted Answer · 2022-09-03T15:40:23.223

4

If you just want to delete the second last character, your can do like this,

s = "[2,3,1,1,]"

s[:-2] + s[-1]
# '[2,3,1,1]'

s[:-2] -> Will slice the string from 0 to -2 index location (without -2 index)

s[-1] -> Will fetch the last element

s[:-2] + s[-1] -> concatenation of the strigs

edited Sep 03 '22 at 15:40

answered Sep 03 '22 at 15:23

Rahul K P

15,740
4
35
52

This answer would be improved by explaining what you're doing. – Chris Sep 03 '22 at 15:36
@Chris Make sense, updated it. – Rahul K P Sep 03 '22 at 15:40

ti7 · Answer 2 · 2022-09-03T15:21:43.940

1

If you're sure you have that string, slice both characters and add the ] back on!

source_string = "[2,3,1,1,]"
if source_string.endswith(",]"):
    source_string = source_string[:-2] + "]"

However, often lists stored as strings are not very useful - you may really want to convert the whole thing to a collection of numbers (perhaps manually removing the "[]" and splitting by ,, or using ast.literal_eval()), potentially converting it back to a string to display later

>>> source_string = "[2,3,1,1,]"
>>> import ast
>>> my_list = ast.literal_eval(source_string)
>>> my_list
[2, 3, 1, 1]
>>> str(my_list)
'[2, 3, 1, 1]'

edited Sep 03 '22 at 15:21

answered Sep 03 '22 at 15:17

ti7

16,375
6
40
68

Thank you, did not know that endswith() even existed. – ili Sep 03 '22 at 15:19
Note that this changes the spacing. maybe `f"[{','.join(map(str, my_list))}]"` – Chris Sep 03 '22 at 15:28

Mohamed Darwesh · Answer 3 · 2022-09-03T16:18:57.017

You can use this for this one case

txt = "[2,3,1,1,]"
print(f"{txt[:-2]}{txt[-1]}")

Even tho storing lists as string is a bit weird

txt[:-2] will get the characters from 0 index to -2 index

txt[-1] will get the last character which is "]"

then I concatenate both with an f"" string

You can use this if you don't wanna use an f string

print(txt[:-2], txt[-1], sep="")

the "sep" argument is so there won't be space between the two prints

cards · Answer 4 · 2022-09-03T19:42:25.277

Using built-in functions such as str.rstrip

l = '[2,3,1,1,]'

l_new = f"{l.rstrip('],')}]" # it doesn't matter the order!
print(l_new)

or str.rpartition

a, _, b = l.rpartition(',')
l_new = a + b
print(l_new)

you can avoid an explicit slicing. See doc for details.

The 1st approach is universal, hence doesn't produce any side-effects. The 2nd may give rise to side-effects if the final last character is not a ,. If necessary use a check, i.e. str.endswith, to fix it.

Slicing the second last character

4 Answers4