Format of string is any of the following... language is ruby
#word > subcategory
#word word > sub / category
#word > sub category
#word word > subcategory
I just want to match the "word" or "word word" (two words with a space)
So far I have this but its not matching the space
scan(/#([^ ]*)/)[0]
Also, for the second one it appears to be working however certain phrases arent matching even though they're identical. I have no idea why. Is there something wrong with the following? (this is to match "subcategory" or "sub category"
scan(/.* > (.*)$/)[0]
The first portion is letters only, the second portion can have any number of spaces, words, characters like / or _
Try this:
^#([^>]*)
[^>]* will match anything until the first > (or the end of the text).
^ is not really needed, but it may protect you from mistakes (for example, if the category contains another hash sign)
Working example: http://rubular.com/r/LO6T9AV3rp
Note that you can match both the word and the category on the same match, for example, using the pattern:
^#([^>]*)>(.*)$
You can capture both groups, and use them:
s = "#word word > sub / category"
m = s.scan(/^#([^>]*)>(.*)$/)
puts m[0]
puts m[1]
Working example: http://ideone.com/SPlvm
I don't quite understand your question.
Do you want to retrive XXX and YYY in the form of "#XXX > YYY"?
In that case, following regular expression will help:
scan(/#([^>]*?) *> *(.*)$/)
For example:
> "#world world > sub / category".scan(/#([^>]*?) *> *(.*)$/)
=> [["world world", "sub / category"]]
Related
Assuming I have 2 array of strings
position1 = ['word1', 'word2', 'word3']
position2 = ['word4', 'word1']
and I want inside a text/string to check if the substring #{target} which exists in text is followed by either one of the words of position1 or following one of the words of the position2 or even both at the same time. Similarly as if I am looking left and right of #{target}.
For example in the sentence "Writing reports and inputting data onto internal systems, with regards to enforcement and immigration papers" if the target word is data I would like to check if the word left (inputting) and right (onto) are included in the arrays or if one of the words in the arrays return true for the regex match. Any suggestions? I am using Ruby and I have tried some regex but I can't make it work yet. I also have to ignore any potential special characters in between.
One of them:
/^.*\b(#{joined_position1})\b.*$[\s,.:-_]*\b#{target}\b[\s,.:-_\\\/]*^.*\b(#{joined_position2})\b.*$/i
Edit:
I figured out this way with regex to capture the word left and right:
(\S+)\s*#{target}\s*(\S+)
However what could I change if I would like to capture more than one words left and right?
If you have two arrays of strings, what you can do is something like this:
matches = /^.+ (\S+) #{target} (\S+) .+$/.match(text)
if matches and (position1.include?(matches[1]) or position2.include?(matches[2]))
do_something()
end
What this regex does is match the target word in your text and extract the words next to it using capture groups. The code then compares those words against your arrays, and does something if they're in the right places. A more general version of this might look like:
def checkWords(target, text, leftArray, rightArray, numLeft = 1, numRight = 1)
# Build the regex
regex = "^.+"
regex += " (\S+)" * numLeft
regex += " #{target}"
regex += " (\S+)" * numRight
regex += " .+$"
pattern = Regexp.new(regex)
matches = pattern.match(text)
return false if !matches
for i in 1..numLeft
return false if (!leftArray.include?(matches[i]))
end
for i in 1..numRight
return false if (!rightArray.include?(matches[numLeft + i]))
end
return true
end
Which can then be invoked like this:
do_something() if checkWords("data", text, position1, position2, 2, 2)
I'm pretty sure it's not terribly idiomatic, but it gives you a general sense of how you would do what you in a more general way.
I'm just learning Ruby and have been tackling small code projects to accelerate the process.
What I'm trying to do here is read only the alphabetic words from a text file into an array, then delete the words from the array that are less than 5 characters long. Then where the stdout is at the bottom, I'm intending to use the array. My code currently works, but is very very slow since it has to read the entire file, then individually check each element and delete the appropriate ones. This seems like it's doing too much work.
goal = File.read('big.txt').split(/\s/).map do |word|
word.scan(/[[:alpha:]]+/).uniq
end
goal.each { |word|
if word.length < 5
goal.delete(word)
end
}
puts goal.sample
Is there a way to apply the criteria to my File.read block to keep it from mapping the short words to begin with? I'm open to anything that would help me speed this up.
You might want to change your regex instead to catch only words longer than 5 characters to begin with:
goal = File.read('C:\Users\bkuhar\Documents\php\big.txt').split(/\s/).flat_map do |word|
word.scan(/[[:alpha:]]{6,}/).uniq
end
Further optimization might be to maintain a Set instead of an Array, to avoid re-scanning for uniqueness:
goal = Set.new
File.read('C:\Users\bkuhar\Documents\php\big.txt').scan(/\b[[:alpha:]]{6,}\b/).each do |w|
goal << w
end
In this case, use the delete_if method
goal => your array
goal.delete_if{|w|w.length < 5}
This will return a new array with the words of length lower than 5 deleted.
Hope this helps.
I really don't understand what a lot of the stuff you are doing in the first loop is for.
You take every chunk of text separated by white space, and map it to a unique value in an array generated by chunking together groups of letter characters, and plug that into an array.
This is way too complicated for what you want. Try this:
goal = File.readlines('big.txt').select do |word|
word =~ /^[a-zA-Z]+$/ &&
word.length >= 5
end
This makes it easy to add new conditions, too. If the word can't contain 'q' or 'Q', for example:
goal = File.readlines('big.txt').select do |word|
word =~ /^[a-zA-Z]+$/ &&
word.length >= 5 &&
! word.upcase.include? 'Q'
end
This assumes that each word in your dictionary is on its own line. You could go back to splitting it on white space, but it makes me wonder if the file you are reading in is written, human-readable text; a.k.a, it has 'words' ending in periods or commas, like this sentence. In that case, splitting on whitespace will not work.
Another note - map is the wrong array function to use. It modifies the values in one array and creates another out of those values. You want to select certain values from an array, but not modify them. The Array#select method is what you want.
Also, feel free to modify the Regex back to using the :alpha: tag if you are expecting non-standard letter characters.
Edit: Second version
goal = /([a-z][a-z']{4,})/gi.match(File.readlines('big.txt').join(" "))[1..-1]
Explanation: Load a file, and join all the lines in the file together with a space. Capture all occurences of a group of letters, at least 5 long and possibly containing but not starting with a '. Put all those occurences into an array. the [1..-1] discards "full match" returned by the MatchData object, which would be all the words appended together.
This works well, and it's only one line for your whole task, but it'll match
sugar'
in
I'd like some 'sugar', if you know what I mean
Like above, if your word can't contain q or Q, you could change the regex to
/[a-pr-z][a-pr-z']{4,})[ .'",]/i
And an idea - do another select on goal, removing all those entries that end with a '. This overcomes the limitations of my Regex
Lets say I have the following string and I want the below output without requiring csv.
this, "what I need", to, do, "i, want, this", to, work
this
what i need
to
do
i, want, this
to
work
This problem is a classic case of the technique explained in this question to "regex-match a pattern, excluding..."
We can solve it with a beautifully-simple regex:
"([^"]+)"|[^, ]+
The left side of the alternation | matches complete "quotes" and captures the contents to Group1. The right side matches characters that are neither commas nor spaces, and we know they are the right ones because they were not matched by the expression on the left.
Option 2: Allowing Multiple Words
In your input, all tokens are single words, but if you also want the regex to work for my cat scratches, "what I need", your dog barks, use this:
"([^"]+)"|[^, ]+(?:[ ]*[^, ]+)*
The only difference is the addition of (?:[ ]*[^, ]+)* which optionally adds spaces + characters, zero or more times.
This program shows how to use the regex (see the results at the bottom of the online demo):
subject = 'this, "what I need", to, do, "i, want, this", to, work'
regex = /"([^"]+)"|[^, ]+/
# put Group 1 captures in an array
mymatches = []
subject.scan(regex) {|m|
$1.nil? ? mymatches << $& : mymatches << $1
}
mymatches.each { |x| puts x }
Output
this
what I need
to
do
i, want, this
to
work
Reference
How to match (or replace) a pattern except in situations s1, s2, s3...
Article about matching a pattern unless...
I have a string named "string" that contains six lines.
I want to remove an "Z" from the end of each line (which each has) and capitalize the first character in each line (ignoring numbers and white space; e.g., "1. apple" -> "1. Apple").
I have some idea of how to do it, but have no idea how to do it in Ruby. How do I accomplish this? A loop? What would the syntax be?
Using regular expression (See String#gsub):
s = <<EOS
1. applez
2. bananaz
3. catz
4. dogz
5. elephantz
6. fruitz
EOS
puts s.gsub(/z$/i, '').gsub(/^([^a-z]*)([a-z])/i) { $1 + $2.upcase }
# /z$/i - to match a trailing `z` at the end of lines.
# /^([^a-z]*)([a-z])/i - to match leading non-alphabets and alphabet.
# capture them as group 1 ($1), group 2 ($2)
output:
1. Apple
2. Banana
3. Cat
4. Dog
5. Elephant
6. Fruit
I would approach this by breaking your problem into smaller steps. After we've solved each of the smaller problems, you can put it all back together for a more elegant solution.
Given the initial string put forth by falsetru:
s = <<EOS
1. applez
2. bananaz
3. catz
4. dogz
5. elephantz
6. fruitz
EOS
1. Break your string into an array of substrings, separated by the newline.
substrings = s.split(/\n/)
This uses the String class' split method and a regular expression. It searches for all occurrences of newline (backslash-n) and treats this as a delimiter, splitting the string into substrings based on this delimiter. Then it throws all of these substrings into an array, which we've named substrings.
2. Iterate through your array of substrings to do some stuff (details on what stuff later)
substrings.each do |substring|
.
# Do stuff to each substring
.
end
This is one form for how you iterate across an array in Ruby. You call the Array's each method, and you give it a block of code which it will run on each element in the array. In our example, we'll use the variable name substring within our block of code so that we can do stuff to each substring.
3. Remove the z character at the end of each substring
substrings.each do |substring|
substring.gsub!(/z$/, '')
end
Now, as we iterate through the array, the first thing we want to do is remove the z character at the end of each string. You do this with the gsub! method of String, which is a search-and-replace method. The first argument for this method is the regular expression of what you're looking for. In this case, we are looking for a z followed by the end-of-string (denoted by the dollar sign). The second argument is an empty string, because we want to replace what's been found with nothing (another way of saying - we just want to remove what's been found).
4. Find the index of the first letter in each substring
substrings.each do |substring|
substring.gsub!(/z$/, '')
index = substring.index(/[a-zA-Z]/)
end
The String class also has a method called index which will return the index of the first occurrence of a string that matches the regular expression your provide. In our case, since we want to ignore numbers and symbols and spaces, we are really just looking for the first occurrence of the very first letter in your substring. To do this, we use the regular expression /[a-zA-Z]/ - this basically says, "Find me anything in the range of small A to small Z or in big A to big Z." Now, we have an index (using our example strings, the index is 3).
5. Capitalize the letter at the index we have found
substrings.each do |substring|
substring.gsub!(/z$/, '')
index = substring.index(/[a-zA-Z]/)
substring[index] = substring[index].capitalize
end
Based on the index value that we found, we want to replace the letter at that index with that same letter, but capitalized.
6. Put our substrings array back together as a single-string separated by newlines.
Now that we've done everything we need to do to each substring, our each iterator block ends, and we have what we need in the substrings array. To put the array back together as a single string, we use the join method of Array class.
result = substrings.join("\n")
With that, we now have a String called result, which should be what you're looking for.
Putting It All Together
Here is what the entire solution looks like, once we put together all of the steps:
substrings = s.split(/\n/)
substrings.each do |substring|
substring.gsub!(/z$/, '')
index = substring.index(/[a-zA-Z]/)
substring[index] = substring[index].capitalize
end
result = substrings.join("\n")
The quiz problem:
You are given the following short list of movies exported from an Excel comma-separated values (CSV) file. Each entry is a single string that contains the movie name in double quotes, zero or more spaces, and the movie rating in double quotes. For example, here is a list with three entries:
movies = [
%q{"Aladdin", "G"},
%q{"I, Robot", "PG-13"},
%q{"Star Wars","PG"}
]
Your job is to create a regular expression to help parse this list:
movies.each do |movie|
movie.match(regexp)
title,rating = $1,$2
end
# => for first entry, title should be Aladdin, rating should be G,
# => WITHOUT the double quotes
You may assume movie titles and ratings never contain double-quote marks. Within a single entry, a variable number of spaces (including 0) may appear between the comma after the title and the opening quote of the rating.
Which of the following regular expressions will accomplish this? Check all that apply.
regexp = /"([^"]+)",\s*"([^"]+)"/
regexp = /"(.*)",\s*"(.*)"/
regexp = /"(.*)", "(.*)"/
regexp = /(.*),\s*(.*)/
Would someone explain why the answer was (1) and (2)?
Would someone explain why the answer was (1) and (2)?
The resulting strings will be similar to "Aladdin", "G" let's take a look at the correct answer #1:
/"([^"]+)",\s*"([^"]+)"/
"([^"]+)" = at least one character that is not a " surrounded by "
, = a comma
\s* = a number of spaces (including 0)
"([^"]+)" = like first
Which is exactly the type of strings you will get. Let's take a look at the above string:
"Aladdin", "G"
#^1 ^2^3^4
Now let's take at the second correct answer:
/"(.*)",\s*"(.*)"/
"(.*)" = any number (including 0) of almost any character surrounded by ".
, = a comma
\s* = any number of spaces (including 0)
"(.*)" = see first point
Which is correct as well as the following irb session (using Ruby 1.9.3) shows:
'"Aladdin", "G"'.match(/"([^"]+)",\s*"([^"]+)"/) # number 1
# => #<MatchData "\"Aladdin\", \"G\"" 1:"Aladdin" 2:"G">
'"Aladdin", "G"'.match(/"(.*)",\s*"(.*)"/) # number 2
# => #<MatchData "\"Aladdin\", \"G\"" 1:"Aladdin" 2:"G">
Just for completeness I'll tell why the third and fourth are wrong as well:
/"(.*)", "(.*)"/
The above regex is:
"(.*)" = any number (including 0) of almost any character surrounded by "
, = a comma
= a single space
"(.*)" = see first point
Which is wrong because, for example, Aladdin takes more than one character (the first point) as the following irb session shows:
'"Aladdin", "G"'.match(/"(.*)", "(.*)"/) # number 3
# => nil
The fourth regex is:
/(.*),\s*(.*)/
which is:
(.*) = any number (including 0) of almost any character
, = a comma
\s* = any number (including 0) of spaces
(.*) = see first point
Which is wrong because the text explicitly says that the movie titles do not contain any number of " character and that are surrounded by double quotes. The above regex does not checks for the presence of " in movie titles as well as the needed surrounding double quotes, accepting strings like "," (which are not valid) as the following irb session shows:
'","'.match(/(.*),\s*(.*)/) # number 4
# => #<MatchData "\",\"" 1:"\"" 2:"\"">