I have a string like this:
Hi my name is John (aka Johnator).
What is the best way to get what comes between the parentheses (including the parentheses)?
You can use String#[] with a regular expression:
a = "Hi my name is John (aka Johnator)"
a[/\(.*?\)/]
# => "(aka Johnator)"
Use [^()]*? for select text in parenthese :
a = "Hi (a(b)c) ((d)"
# => "Hi (a(b)c) ((d)"
a.gsub(/\([^()]*?\)/) { |x| p x[1..-2]; "w"}
"b"
"d"
# => "Hi (awc) (w"
Try this:
str1 = ""
text = "Hi my name is John (aka Johnator)"
text.sub(/(\(.*?\))/) { str1 = $1 }
puts str1
Edit: Didn't read about leaving the parenthesis!
Related
I have two strings, and want to determine if the two string start with the same sub string.
str1 = "The cat is black. jkhdkjhdsjhd"
str2 = "The cat is black and white."
str1.starts_with_substring? str2
returns "The cat is black"
str1.starts_with_substring? "The cat"
returns "The cat"
str1.starts_with_substring? "Hello, World!""
returns nil
I think I could do this with an iterator, but I was hoping for something more built in.
You can use start_with? and all? for that:
str1 = "The cat is black. jkhdkjhdsjhd"
str2 = "The cat is black and white."
p [str1, str2].all? { |str| str.start_with?('The cat is') } # true
p [str1, str2].all? { |str| str.start_with?('The cat is not') } # false
And as from Ruby 2.5 Enumerable#any?, all?, none? and one? accept a pattern as argument, you can pass a regular expression to check if each string starts with that substring:
str1 = "The cat is black. jkhdkjhdsjhd"
str2 = "The cat is black and white."
str3 = "renuncia Piñera The cat is black and white."
p [str1, str2].all?(/\AThe cat is /) # true
p [str1, str2, str3].all?(/\AThe cat is /) # false
After seeing the question in comments, this might work:
str1 = "The cat is black."
str2 = "The cat is black and white."
str3 = "The cat"
def all_substring?(sentences)
length = sentences.min.length
sentences.map { |sentence| sentence[0...length] }.uniq == [sentences.sample[0...length]]
end
p all_substring?([str1, str2, str3]) # true
If you can't know beforehand if there's a substring which what to look for, I think you can use the smallest sentence as the substring.
def well_do_they?(str1, str2, str)
len = str.size
str == str1[0,len] && str == str2[0,len]
end
Any monkey patch to String Class?
module MyStringPatch
def starts_with_substring(other)
return nil if self[0] != other[0]
n = (0..self.size).each { |n| break n if self[0..n] != other[0..n] }
self[0..n-1]
end
end
String.include MyStringPatch
So you can call
str1 = "The cat is black. jkhdkjhdsjhd"
str2 = "The cat is black and white."
str1.starts_with_substring str2 #=> "The cat is black"
str1.starts_with_substring "The cat" #=> "The cat"
str1.starts_with_substring "Hello, World!" #=> nil
string = 'The cat is black.'
str1 = 'The cat is black and white.'
str2 = 'The cat'
str3 = 'The dog is white'
def matched_substrings(string, *substrings)
string = string.gsub('.', '')
substrings.select do |substring|
substring = substring.gsub('.', '')
string.start_with?(substring) || substring.start_with?(string)
end
end
matched_substrings(string, str1, str2, str3)
#=> ["The cat is black and white.", "The cat"]
How to replace a file in Ruby, but do not touch commented-out lines? To be more specific I want to change variable in configuration file. An example would be:
irb(main):014:0> string = "#replaceme\n\t\s\t\s# replaceme\nreplaceme\n"
=> "#replaceme\n\t \t # replaceme\nreplaceme\n"
irb(main):015:0> puts string.gsub(%r{replaceme}, 'replaced')
#replaced
# replaced
replaced
=> nil
irb(main):016:0>
Desired output:
#replaceme
# replaceme
replaced
I don't fully understand the question. To do a find and replace in each line, disregarding text following a pound sign, one could do the following.
def replace_em(str, source, replacement)
str.split(/(\#.*?$)/).
map { |s| s[0] == '#' ? s : s.gsub(source, replacement) }.
join
end
str = "It was known that # that dog has fleas, \nbut who'd know that that dog # wouldn't?"
replace_em(str, "that", "the")
#=> "It was known the # that dog has fleas, \nbut who'd know the the dog # wouldn't?"
str = "#replaceme\n\t\s\t\s# replaceme\nreplaceme\n"
replace_em(str, "replaceme", "replaced")
#=> "#replaceme\n\t \t # replaceme\nreplaced\n"
For the string
str = "It was known that # that dog has fleas, \nbut who'd know that that dog # wouldn't?"
source = "that"
replacement = "the"
the steps are as follows.
a = str.split(/(\#.*?$)/)
#=> ["It was known that ", "# that dog has fleas, ",
# "\nbut who'd know that that dog ", "# wouldn't?"]
Note that the body of the regular expression must be put in a capture group in order that the text used to split the string be included as elements in the resulting array. See String#split.
b = a.map { |s| s[0] == '#' ? s : s.gsub(source, replacement) }
#=> ["It was known the ", "# that dog has fleas, ",
# "\nbut who'd know the the dog ", "# wouldn't?"]
b.join
#=> "It was known the # that dog has fleas, \nbut who'd know the the dog # wouldn't?"
How about this?
puts string.gsub(%r{^replaceme}, 'replaced')
Is is possible to create/use a regular expression pattern in ruby that is based on the value of a variable name?
For instance, we all know we can do the following with Ruby strings:
str = "my string"
str2 = "This is #{str}" # => "This is my string"
I'd like to do the same thing with regular expressions:
var = "Value"
str = "a test Value"
str.gsub( /#{var}/, 'foo' ) # => "a test foo"
Obviously that doesn't work as listed, I only put it there as an example to show what I'd like to do. I need to regexp match based on the value of a variable's content.
The code you think doesn't work, does:
var = "Value"
str = "a test Value"
p str.gsub( /#{var}/, 'foo' ) # => "a test foo"
Things get more interesting if var can contain regular expression meta-characters. If it does and you want those matacharacters to do what they usually do in a regular expression, then the same gsub will work:
var = "Value|a|test"
str = "a test Value"
str.gsub( /#{var}/, 'foo' ) # => "foo foo foo"
However, if your search string contains metacharacters and you do not want them interpreted as metacharacters, then use Regexp.escape like this:
var = "*This*"
str = "*This* is a string"
p str.gsub( /#{Regexp.escape(var)}/, 'foo' )
# => "foo is a string"
Or just give gsub a string instead of a regular expression. In MRI >= 1.8.7, gsub will treat a string replacement argument as a plain string, not a regular expression:
var = "*This*"
str = "*This* is a string"
p str.gsub(var, 'foo' ) # => "foo is a string"
(It used to be that a string replacement argument to gsub was automatically converted to a regular expression. I know it was that way in 1.6. I don't recall which version introduced the change).
As noted in other answers, you can use Regexp.new as an alternative to interpolation:
var = "*This*"
str = "*This* is a string"
p str.gsub(Regexp.new(Regexp.escape(var)), 'foo' )
# => "foo is a string"
It works, but you need to use gsub! or assign the return to another variable
var = "Value"
str = "a test Value"
str.gsub!( /#{var}/, 'foo' ) # Or this: new_str = str.gsub( /#{var}/, 'foo' )
puts str
Yes
str.gsub Regexp.new(var), 'foo'
You can use regular expressions through variables in ruby:
var = /Value/
str = "a test Value"
str.gsub( /#{var}/, 'foo' )
str.gsub( Regexp.new("#{var}"), 'foo' )
Lets say i want to remove leading space from a string
a = " Hello world"
puts a.gsub!(/^ /,"") # => "Hello World"
But if there is no leading space in the string
b = "Hello World"
puts a.gsub!(/^ /,"") # => nil
Now if I use just gsub instead of gsub it returns the string:
puts b.gsub(/^ /,"") # => "Hello World"
puts a.gsub(/^ /,"") # => "Hello World" (works for both a and b)
So is it possible to get gsub! to perform like gsub as shown above?
the reason is because gsub would create a new object everytime which I would like to avoid because I will be using at least 4 or 5 gsubs on the string I need to manipulate.
thanks
Here are two ways of doing that.
Add || a to the gsub expression
a.gsub!(/\A\s/,"") || a
would give you the desired result, namely removing the space, if present, and returning the string after any change is made. If no change is made, this reduces to nil || a #=> a. If a change is made the expression reduces to a.gsub!(/\A\s/,""). For example,
a = " Hello"
a.gsub!(/\A\s/,"") || a #=> "Hello"
a #=> "Hello"
a ="Hello"
a.gsub!(/\A\s/,"") || a #=> "Hello"
a #=> "Hello"
Although it makes no difference here, I prefer to use the beginning of string anchor, \A, rather than the beginning of line anchor, ^, I also prefer using a whitespace character \s to a space (assuming it couldn't be a tab) to a space, as an inadvertent extra space might not be noticed.
Use String#replace and the non-destructive method String#gsub
a = " Hello"
a.replace(a.gsub(/\A\s/,"")) #=> "Hello"
a #=> "Hello"
a ="Hello"
a.replace(a.gsub(/\A\s/,"")) #=> "Hello"
a #=> "Hello"
Answer:
b.gsub!(/(^ )?/,"") => "Hello World"
Explanation:
(...) Capture everything enclosed
a? Zero or one of a
— via http://rubular.com
Example:
irb(main):008:0> a = " Hello World"
=> " Hello World"
irb(main):009:0> b = "Hello World"
=> "Hello World"
irb(main):010:0> a.gsub!(/(^ )?/,"")
=> "Hello World"
irb(main):011:0> b.gsub!(/(^ )?/,"")
=> "Hello World"
Alternative:
b.gsub!(/^ |/,"") # => "Hello World" using "OR" pipe char
The code below adds a method to the String class that simply calls gsub! and then returns the String object that it was called on. So if the gsub! was "successful" and something has been subbed it returns the subbed string. Otherwise it will return the original string.
class String
def filled_gsub!(oldsubstr, newsubstr)
gsub!(oldsubstr, newsubstr)
self
end
end
I'd like to replace/duplicate a substring, between two delimeters -- e.g.,:
"This is (the string) I want to replace"
I'd like to strip out everything between the characters ( and ), and set that substr to a variable -- is there a built in function to do this?
I would just do:
my_string = "This is (the string) I want to replace"
p my_string.split(/[()]/) #=> ["This is ", "the string", " I want to replace"]
p my_string.split(/[()]/)[1] #=> "the string"
Here are two more ways to do it:
/\((?<inside_parenthesis>.*?)\)/ =~ my_string
p inside_parenthesis #=> "the string"
my_new_var = my_string[/\((.*?)\)/,1]
p my_new_var #=> "the string"
Edit - Examples to explain the last method:
my_string = 'hello there'
capture = /h(e)(ll)o/
p my_string[capture] #=> "hello"
p my_string[capture, 1] #=> "e"
p my_string[capture, 2] #=> "ll"
var = "This is (the string) I want to replace"[/(?<=\()[^)]*(?=\))/]
var # => "the string"
str = "This is (the string) I want to replace"
str.match(/\((.*)\)/)
some_var = $1 # => "the string"
As I understand, you want to remove or replace a substring as well as set a variable equal to that substring (sans the parentheses). There are many ways to do this, some of which are slight variants of the other answers. Here's another way that also allows for the possibility of multiple substrings within parentheses, picking up from #sawa's comments:
def doit(str, repl)
vars = []
str.gsub(/\(.*?\)/) {|m| vars << m[1..-2]; repl}, vars
end
new_str, vars = doit("This is (the string) I want to replace", '')
new_str # => => "This is I want to replace"
vars # => ["the string"]
new_str, vars = doit("This is (the string) I (really) want (to replace)", '')
new_str # => "This is I want"
vars # => ["the string", "really, "to replace"]
new_str, vars = doit("This (short) string is a () keeper", "hot dang")
new_str # => "This hot dang string is a hot dang keeper"
vars # => ["short", ""]
In the regex, the ? in .*? makes .* "lazy". gsub passes each match m to the block; the block strips the parens and adds it to vars, then returns the replacement string. This regex also works:
/\([^\(]*\)/