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please is in ruby possible to get information from example name "Doe,Jon" (exact format) to get only the name "Jon"? Of course the name can be always different, I was thinking if is not possible to get the value from end of string to "," separator. If is it possible, how?
Thanks for your help.
So lets examine some of the solutions that are given to you in the comments
Split
"Doe,Jon".split(',').last
# or a bit more verbose
parts = "Doe,Jon".split(',') # ["Doe", "Jon"]
name = parts.last # "Jon"
String#split splits a sting into an array. It uses the parameter "," as separator. Array#last returns the last item from an array.
Gsub
"Doe,Jon".gsub(/.*,/, '')
String#gsub substitutes the part that matches the Regular Expression (/.*,/) with the substitution value ("").
The regexp matches everything (.*) up to (and including) the comma. And the replacement is an empty string, essentially deleting the part that matches the regexp.
Note that you could/should probably have an anchor to make the regexp more strict (/\A.*,/)
Slice
String#slice creates a substring given a range. -1 is a shortcut for the last element.
String#index finds the index of a character inside a String.
"Doe,Jon".slice(("Doe,Jon".index(',')+1)..-1)
# or more verbose
full = "Doe,Jon"
index_of_comma = full.index(',') # => 3
index_after_comma = index + 1
name = full.slice(index_after_comma..full.size)
CSV
CSV (Comma Separated Values) is a format where multiple values are separated by a comma (or other separation character).
require "csv"
CSV.parse("John,Doe")[0][1]
This will treat the name as CSV data and then access the first row of data (´[0]´). And from that row accesses the second element ([1]) which is the name.
Now what?
There are usually multiple ways to reach a goal. And it's up to you to pick a way. I'd go with the first one. To me it is easy to read and understand its purpose.
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I want to write a simple program to collect data from pieces of texts by creating regular expressions to identify values through the phrases of the texts.
I want to start from something simple:
The car is red
I´m looking for a expression that let me to store the value red, or other possibles values such as blue, yellow, green if phrase changes. I want to do that from the interpreter or from a .txt file.
So my questions has two parts. One is to specify the value I want save. In this case "red", So I imagine a piece of code like {"The car is 'value'"} => value #color...Whatever be the regular expression that capture the syntax pattern of the language, Sorry I am not yet very familiar with the syntax of ruby , that's about precisely my question.
And the other part is about creating a variable to store the string "red" or whatever would be the case: yellow, green, brown...
I hope the question be clear.
It's pretty simple using a match group:
string = "The car is red. The car is blue"
regex = /The car is (\w+)/
matches = string.scan(regex)
print matches
# => [["red"], ["blue"]]
print matches.flatten(1)
# => ["red", "blue"]
(\w+) in the regex is the match group. The parenthesis are the start and end bounds of the match. The match is what will be returned by scan. You can use multiple match groups if you want.
\w in regex is a non-word-boundary character. \w+ effectively captures one word.
cucumber makes use of this approach
You need to build a regular expression that will extract desired word from the input. You can read about it in the official documentation about Regexp class. You can also use rubular.com to test and play with expressions on sample data. You can assign match result to a variable in Ruby in the following way:
match = "The car is red".match(/red/)
color = match[0] unless match.nil?
or in a single line:
color, *_ = "The car is red".match(/red/).to_a
# color => "red"
color, *_ = "The car is red".match(/blue/).to_a
# color => nil
match method can extract multiple variables at once. In the sample code above, we've used only one (color). The method returns MatchData object as the result. Calling to_a will convert it to the array (note that empty match will produce an empty array so it is safe in this case). At the end you can assign it to a variable and forget the rest of results (they will be single variable in array anyway).
I didn't provide you a regexp, because this is a topic that you can learn your self depending on the use case (for your simple example, there is an example in the another answer).
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i am constructing a program in Ruby which requires the value to be extracted between the 2nd and 3rd full-stop in a string.
I have searched online for various related solutions, including truncation and this prior Stack-Overflow question: Get value between 2nd and 3rd comma, however no answer illustrated a solution in the Ruby language.
Thanks in Advance.
list = my_string.split(".")
list[2]
That will do it I think. First command splits it into a list. Second gets the bit you want
You could split the string on full stops (aka periods), but that creates an array with one element for each substring preceding a full stop. If the document had, say, one million such substrings, that would be a rather inefficient way of getting just the third one.
Suppose the string is:
mystring =<<_
Now is the time
for all Rubiests
to come to the
aid of their
bowling team.
Or their frisbee
team. Or their
air guitar team.
Or maybe something
else...
_
Here are a couple of approaches you could take.
#1 Use a regular expression
r = /
(?: # start a non-capture group
.*?\. # match any character any number of times, lazily, followed by a full stop
){2} # end non-capture group and perform operation twice
\K # forget everything matched before
[^.]* # match everything up to the next full stop
/xm # extended/free-spacing regex definition mode and multiline mode
mystring[r]
#=> " Or their\nair guitar team"
You could of course write the regex:
r = /(?:.*?\.){2}\K[^.]*/m
but the extended form makes it self-documenting.
The regex engine will step through the string until it finds a match or concludes that there can be no match, and stop there.
#2 Pretend a full stop is a newline
First suppose we were looking for the third line, rather than the third substring followed by a full stop. We could write:
mystring.each_line.take(3).last.chomp
# => "to come to the"
Enumerable#take determines when a line ends by examining the input record separator, which is held by the global variable $/. By default, $/ equals a newline. We therefore could do this:
irs = $/ # save old value, normally \n
$/ = '.'
mystring.each_line.take(3).last[0..-2]
#=> " Or their\nair guitar team"
Then leave no footprints:
$/ = irs
Here String#each_line returns an enumerator (in effect, a rule for determining a sequence of values), not an array.
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I'm looking to modify a string as follows:
"one hundred forty-four".sub(/(\w+)(\s)([a-z\-]+)$/){$2 = "test"}
say.rb:78: Can't set variable $2
How can I do that?
edit: one hundredtestforty-four is what i want.
It is not allowed. It is a read only global variable.
Using another global variable name it works fine.
Of course, using global variables bring concerns of clobbering other parts of your program.
I believe you want:
"one hundred forty-four".sub(/\s+([a-z-]+)$/, 'test\1')
#=> "one hundredtestforty-four"
or
"one hundred forty-four".sub(/\s+([a-z-]+)$/, "test\\1")
#=> "one hundredtestforty-four"
or
"one hundred forty-four".sub(/\s+([a-z-]+)$/, "test"+$1)
#=> "one hundredtestforty-four"
or
"one hundred forty-four".sub(/\s+([a-z-]+)$/, "test#{$1}")
#=> "one hundredtestforty-four"
The regex looks for a string that starts with one or more spaces, then any number of lowercase letters or hypens, followed by an end-of-line. (Note the hypen is not escaped within a character class, and it must be appear first or last within the class). It therefore matches " forty-four", with capture group 1 containing "forty-four". Ergo, " forty-four" is replaced with "testforty-four". Notice that you retrieve the contents of capture group 1 by writing \1 if the string is written with single quotes, \\1 if double-quotes are used. Alternatively, you can use the global variable in one of two ways shown.
Note that, if desired, you can use $1 to reference the contents of capture group 1 in subsequent statements.
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I would like to start a new line after every 66 characters for any file that is input into a Ruby script.
some_string.insert( 66, "\n" )
puts some_string
shows that a new line starts after the 66th character but I need it to happen after each 66th character. In other words, each line should be 66 characters long (except possibly the last).
I'm sure it involves a regex but I've tried various with insert, scan, gsub and cannot get it to work.
I'm new to Ruby and programming and this is the first thing I've tried outside of a tutorial. Thanks for the information, all.
You could do something like this:
<your_string>.scan(/.{1,66}/).join("\n")
It will basically split <your_string> at every 66th character and then re-join it by adding the \n between each part.
Or this variation to not split words in half:
<your_string>.scan(/.{1,66} /).join("\n")
some_string.gsub(/.{66}/, "\n")
If you're interested in exploring an answer that doesn't use RegEx, try something like:
a = "Your string goes here"
d = 66
Array(0..a.length/d).collect {|j| a[j*d..(j+1)*d-1]}.join("\n")
The RegEx is likely faster, but this uses the Array Constructor, .collect and .join so it might be an interesting learning exercise. The first part generates an array of numbers based on the number of chunks (a.length/d). The collect gathers the substrings in to an array. The body of the collect generates substrings by ranges on the original string, and the join puts it back together with '\n' separators.
Use the following to split the string into an array of strings of length 66 and join those strings with a newline character.
some_string.scan(/.{1,66}/).join("\n")
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I'm having some problems coming up with a regexp that matches class1, class2, and class3 in the following string (ideally I could have n number of words separated by pipes, as the number of classes passed to my method is not constant)
class1|class2|class3 path/to/resource
I have the following matcher which returns only class1. Bonus points to whomever can find me a matcher for the resource path as well.
Edit
Thank you very much for all the help - points all around!
Assuming you are confident that your input will be well formed, my advice would be to split your string by both the pipe character and space. For example:
components = "class1|class2|class3 path/to/resource".split(/[ \|]/)
You would then have access to an array containing n components followed by the path to your resource which you can manipulate to access.
resourcePath = components.pop()
classes = components
EDIT: The original topic of this was suggested the OP is using Ruby, hence my answer.
\w+(\|\w+)*\s+\w+(\/\w+)*
I assumed that the names of your classes consist of one or more word characters. Adjust if they're more restricted than that. For instance, use class\d+ for numbered classes only.
We have a class name, followed by any number of [a pipe followed by a class name]. Then we have one or more spaces, followed by basically the same thing, but this time using slashes instead of pipes.
I've escaped both the pipe and the slash with a backslash.
string = "class1|class2|class3 path/to/resource".split(%r{[| ]})
=> ["class1", "class2", "class3", "path/to/resource"]
I would just do two splits:
string = 'class1|class2|class3 path/to/resource'
p string.split.first.split('|') #=> ["class1", "class2", "class3"]
If you want to use regex with the input you provided, this will extract your classes and path:
([\w/]+)\|? ?
INPUT
class1|class2|class3 path/to/resource
OUTPUT
class1
class2
class3
path/to/resource