Ruby Gsub Multiple Characters in String

Ruby gsub multiple characters in string

String#gsub and Hash#fetch will be the good choice for this.

a = "every good boy does fine"
h = {"every" => "all","boy" => "girl", "fine" =>"well" }
a.gsub(/\w+/) { |m| h.fetch(m,m)}
# => "all good girl does well"

or,

a = "every good boy does fine"
h = {"every" => "all","boy" => "girl", "fine" =>"well" }
Regexp.new("^#{h.keys.join('|')}$") # => /^every|boy|fine$/
a.gsub(Regexp.new("^#{h.keys.join('|')}$"),h)
# => "all good girl does well"

How to replace multiple substrings with same string using `gsub`

to|an|a|the is pattern, you are using it as String. Here:

str.gsub('to|an|a|the', '')   # passing string argument
#=> "How to chop an onion?"

str.gsub(/to|an|a|the/, '')   # passing pattern argument
#=> "How  chop  onion?"

Ruby multiple string replacement

Since Ruby 1.9.2, String#gsub accepts hash as a second parameter for replacement with matched keys. You can use a regular expression to match the substring that needs to be replaced and pass hash for values to be replaced.

Like this:

'hello'.gsub(/[eo]/, 'e' => 3, 'o' => '*')    #=> "h3ll*"
'(0) 123-123.123'.gsub(/[()-,. ]/, '')    #=> "0123123123"

In Ruby 1.8.7, you would achieve the same with a block:

dict = { 'e' => 3, 'o' => '*' }
'hello'.gsub /[eo]/ do |match|
   dict[match.to_s]
 end #=> "h3ll*"

Replacing multiple characters in Ruby string with one character

The easiest I can think of is:

string.tr!("aeiou", "*")

Replace multiple strings in one gsub() or chartr() statement in R?

You can use gsubfn

library(gsubfn)
gsubfn(".", list("'" = "", " " = "_"), x)
# [1] "ab_c"

Similarly, we can also use mgsub which allows multiple replacement with multiple pattern to search

mgsub::mgsub(x, c("'", " "), c("", "_"))
#[1] "ab_c"

How to have gsub handle multiple patterns and replacements

Well, as you can read from the docs, gsub does not handle multiple patterns and replacements at once. That's what causing your error, quite explicit otherwise (you can read that as "give me a String, not an Array!!1").

You can write that like this:

def twitterize(text)
  patterns = [/((([A-Za-z]{3,9}:(?:\/\/)?)(?:[-;:&=\+\$,\w]+@)?[A-Za-z0-9.-]+|(?:www.|[-;:&=\+\$,\w]+@)[A-Za-z0-9.-]+)((?:\/[\+~%\/.\w-_]*)?\??(?:[-\+=&;%@.\w_]*)#?(?:[\w]*))?)/, /(?<=^|(?<=[^a-zA-Z0-9-\.]))@([A-Za-z_]+[A-Za-z0-9_]+)/, /(?<=^|(?<=[^a-zA-Z0-9-\.]))#([A-Za-z_]+[A-Za-z0-9_]+)/]
  replacements =  ["<a href='\\0' target='_blank'>\\0</a>",
            "<a href='http://twitter.com/\\1' target='_blank'>\\0</a>",
            "<a href='http://twitter.com/search?q=\\1&src=hash' target='_blank'>\\0</a>"]

  patterns.each_with_index do |pattern, i|
    text.gsub!(pattern, replacements[i])
  end

  text
end

This can be refactored into more elegant rubyish code, but I think it'll do the job.

Using gsub to strip multiple characters

You should do it in once:

string[/yyyy(.*)zzzz\z/, 1]  

GSUB replace 3 or more repeating characters

When you enclose the whole pattern inside square brackets, you make it match a single char.

Your regexps mean:

• [\/\\1{3,}] - a single char, /, \, 1, {, 3, , or }
• [\/\2+] - /, \u0002 char or +
• [\/{3,}] - /, {, 3, , or }

You can use

s.gsub(/\/{3,}/, '//')

See the Ruby demo online.

Regex for multiple string operations in a single pass?

This uses String#tr to do the substitution in a single pass. This assumes the string consists of printable ASCII characters.

string.tr " \t\nB-DF-HJ-NP-TV-Zb-df-hj-np-tv-z!-@[-`{-~", '&&&*'
# => "*a*e&a**&**e&**a**e*&*i**i*&a&*i***e&*a**"

For tr, - is the range operator. So for the letters B, C, D, since these are consecutive, it can be written as B-D. So B-DF-HJ-NP-TV-Z is basically all the capital letters minus the vowels. Same with lowercase, followed by all printable punctuation on the ASCII chart. These all get replaced by a *. The only 3 whitespace characters that match \s are space, tab, and newline, and these are listed explicitly at the front of the string and are each replaced by &.

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If 2 passes are allowed, then it can be written more concisely as

string.tr(' ','&').tr('^AEIOUaeiou&','*')

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