How to delete specific characters from a string in Ruby?

Question

I have several strings that look like this:

"((String1))"

They are all different lengths. How could I remove the parentheses from all these strings in a loop?

Remove parentheses, or remove first two and last two characters from a "random" string? (Actually random?) — Reinstate Monica -- notmaynard, Oct 28 '13 at 14:42
You are asking for a loop to change many string, how are the strings stored? — hirolau, Oct 28 '13 at 15:01
I know how to make a loop through all the strings i just wanted the string manipulation part, sorry i worded that weird — Cristiano, Oct 28 '13 at 15:31
Here's a solution a chef might like: `def chop_chop(s) chop_one_way(chop_one_way(s,')').reverse,'(').reverse end` and `def chop_one_way(s,c); s.chop! while s[-1] == c; s; end chop_chop "(((abc)))" # => "abc"`. — Cary Swoveland, Oct 28 '13 at 18:07

score 196 · Accepted Answer · edited Jun 03 '15 at 17:34

196

Do as below using String#tr :

 "((String1))".tr('()', '')
 # => "String1"

edited Jun 03 '15 at 17:34

Nakilon

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answered Oct 28 '13 at 14:42

Arup Rakshit

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There's also a destructive version `tr!` that will modify a string in-place, like `my_string.tr!(')(','')` – bonh May 19 '15 at 20:01
11

Note that this function is not trimming from the beginning or end, but a full replacement on all text within the string. – Jordan Dec 21 '17 at 19:41
3

Misleading and incorrect. Tr is not a trimming function, it is a replacement function. The two are very different operations. – Zane Claes May 10 '18 at 15:41
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@ZaneClaes Yes. OP used wrong term to explain what actually the OP wants. The answer has shown how to achieve the output. – Arup Rakshit May 10 '18 at 18:50
AttributeError: 'str' object has no attribute 'tr' – Nathan B Sep 23 '22 at 06:47
@NathanB Ruby version? – Arup Rakshit Sep 24 '22 at 16:28

jbr · Answer 2 · 2013-10-28T15:07:10.153

49

If you just want to remove the first two characters and the last two, then you can use negative indexes on the string:

s = "((String1))"
s = s[2...-2]
p s # => "String1"

If you want to remove all parentheses from the string you can use the delete method on the string class:

s = "((String1))"
s.delete! '()'
p s #  => "String1"

edited Oct 28 '13 at 15:07

answered Oct 28 '13 at 14:44

jbr

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This will delete all parentheses, even those in the middle of the string as well, which (seemingly) is not what OP wants. If that is what is wanted this is the most elegant solution. – Reinstate Monica -- notmaynard Oct 28 '13 at 14:47

score 30 · Answer 3 · answered Aug 18 '15 at 17:59

30

For those coming across this and looking for performance, it looks like #delete and #tr are about the same in speed and 2-4x faster than gsub.

text = "Here is a string with / some forwa/rd slashes"
tr = Benchmark.measure { 10000.times { text.tr('/', '') } }
# tr.total => 0.01
delete = Benchmark.measure { 10000.times { text.delete('/') } }
# delete.total => 0.01
gsub = Benchmark.measure { 10000.times { text.gsub('/', '') } }
# gsub.total => 0.02 - 0.04

answered Aug 18 '15 at 17:59

daino3

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Four years later... :-) I find if I up your benchmarking by a couple orders of magnitude (1_000_000 runs), that with the same code you use above, I do get delete running slightly faster than tr, with delete at about a 0.92 ratio of tr, and gsub a little less than 1.5x of delete (actually ~ 1.46 of delete, and ~ 1.39 of tr). ymmv of course. This is on Ruby 2.6.3 on a 2018 MBP 13. Thanks for benchmarking these three methods! – likethesky Aug 18 '19 at 22:00

score 22 · Answer 4 · answered Oct 28 '13 at 14:41

22

Using String#gsub with regular expression:

"((String1))".gsub(/^\(+|\)+$/, '')
# => "String1"
"(((((( parentheses )))".gsub(/^\(+|\)+$/, '')
# => " parentheses "

This will remove surrounding parentheses only.

"(((((( This (is) string )))".gsub(/^\(+|\)+$/, '')
# => " This (is) string "

answered Oct 28 '13 at 14:41

falsetru

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+1 for the second example (remove surrounding parentheses only). – Bhavneet Singh Bajwa Oct 21 '14 at 11:05

score 1 · Answer 5 · answered Jul 08 '17 at 18:22

1

Here is an even shorter way of achieving this:

1) using Negative character class pattern matching

irb(main)> "((String1))"[/[^()]+/]
=> "String1"

^ - Matches anything NOT in the character class. Inside the charachter class, we have ( and )

Or with global substitution "AKA: gsub" like others have mentioned.

irb(main)> "((String1))".gsub(/[)(]/, '')
=> "String1"

answered Jul 08 '17 at 18:22

z atef

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Your two answers have different results on `((a))b`. The first will only return `a`, the second will return `ab` – Ulysse BN Oct 01 '18 at 12:59

score 1 · Answer 6 · answered Aug 05 '22 at 21:22

1

Use String#delete:

"((String1))".delete "()"
=> "String1"

answered Aug 05 '22 at 21:22

Pavel Chuchuva

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How to delete specific characters from a string in Ruby?

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