I need to create a regular expression to identify key value pairs which are separated by commas. Key and value can have letters (both upper case and lower case), digits, special characters (- _ , / .). Following regular expression works when special characters follow alphanumeric characters but when the special character comes before alphanumeric characters, it does not work. For example "key1.=value1-;key2/=value2-" works but ".key1=value1-;key2/=value2-" does not work.
import scala.util.matching.Regex
object TestReges {
def main(args: Array[String]): Unit = {
//val inputPattern : String= "1one-=1;two=2"
//val inputPattern : String = "-"
//val inputPattern : String= "two"
val inputPattern : String= "key1-=value1;key2=,value2."
val tagValidator: Regex = "(?:(\\w*\\d*-*_*,*/*\\.*)=(\\w*\\d*-*_*,*/*\\.*)(?=;|$))".r
//Pattern p = Pattern.compile("(?:(^[a-z]+)=(^[a-z]+)(?=&|$))");
//Matcher m = p.matcher(input);
//System.out.println(m.groupCount());
println(tagValidator.findAllMatchIn(inputPattern).size)
// while (m.find()) {
// System.out.println("key="+m.group(1));
// System.out.println("value="+m.group(2));
// }
} }
Why not split on the separator and then just match everything on either side of the = that isn't an =?
//Scala code
val kvPair = "([^=]+)=([^=]+)".r
List("key1.=value1-;key2/=value2-",".key1=value1-;key2/=value2-")
.flatMap(_.split(";"))
.collect{case kvPair(k,v) => k -> v}
//res0: List[(String, String)] = List((key1.,value1-)
// , (key2/,value2-)
// , (.key1,value1-)
// , (key2/,value2-))
Why do you want to do it with regex as #shmosel specified why can't you just split it on ; and then on = ? like this
val inputPattern : String= "key1-=value1;key2=,value2."
inputPattern.split(";").map{ kvStr => kvStr.split("=") match
case Array(k, v) => (k, v)
}.toMap
Related
Lets assume I have a string as such:
val a = "aaaabbbcccss"
and I want to group only the a's and b's as such:
"a4b3cccss"
I have tries a.toList.groupBy(identity).mapValues(_.size) but that returns a map with no ordering so I cannot convert it into the form I want. I was wondering if there is a function in scala that can achieve what I want?
You may use
val a = "aaaabbbcccss"
val p = """([ab])\1*""".r
println(p replaceAllIn (a, m => s"${m.group(1)}${m.group(0).size}") )
See Scala demo
The regex matches:
([ab]) - Group 1: a or b
\1* - zero or more occurrences of the char captured into Group 1.
In the replacement part, m.group(1) is the char captured into Group 1 and m.group(0).size is the size of the whole match.
As an alternative, you might create a function which you can give your string and a list of characters and use a recursive approach where you could take consecutive characters from the list using takeWhile.
Then drop from the list using the length of the result from takewhile and add to the accumulator what you want to concatenate to the acc string which will be returned when the list will be empty.
def countSimilar(str: String, ch: List[Char]): String = {
def process(l: List[Char], acc: String = ""): String = {
l match {
case Nil => acc
case h :: _ =>
val tw = l.takeWhile(_ == h)
acc + process(
l.drop(tw.length),
if (ch.contains(h)) h + tw.length.toString else tw.mkString("")
)
}
}
process(str.toList)
}
println(countSimilar("aaaabbbcccss", List('a', 'b')))
println(countSimilar("aaaabbbcccssaaaabb", List('a', 'b', 'c')))
That will give you:
a4b3cccss
a4b3c3ssa4b2
See the Scala demo
My program is:
val pattern = "[*]prefix_([a-zA-Z]*)_[*]".r
val outputFieldMod = "TRASHprefix_target_TRASH"
var tar =
outputFieldMod match {
case pattern(target) => target
}
println(tar)
Basically, I try to get the "target" and ignore "TRASH" (I used *). But it has some error and I am not sure why..
Simple and straight forward standard library function (unanchored)
Use Unanchored
Solution one
Use unanchored on the pattern to match inside the string ignoring the trash
val pattern = "prefix_([a-zA-Z]*)_".r.unanchored
unanchored will only match the pattern ignoring all the trash (all the other words)
val result = str match {
case pattern(value) => value
case _ => ""
}
Example
Scala REPL
scala> val pattern = """foo\((.*)\)""".r.unanchored
pattern: scala.util.matching.UnanchoredRegex = foo\((.*)\)
scala> val str = "blahblahfoo(bar)blahblah"
str: String = blahblahfoo(bar)blahblah
scala> str match { case pattern(value) => value ; case _ => "no match" }
res3: String = bar
Solution two
Pad your pattern from both sides with .*. .* matches any char other than a linebreak character.
val pattern = ".*prefix_([a-zA-Z]*)_.*".r
val result = str match {
case pattern(value) => value
case _ => ""
}
Example
Scala REPL
scala> val pattern = """.*foo\((.*)\).*""".r
pattern: scala.util.matching.Regex = .*foo\((.*)\).*
scala> val str = "blahblahfoo(bar)blahblah"
str: String = blahblahfoo(bar)blahblah
scala> str match { case pattern(value) => value ; case _ => "no match" }
res4: String = bar
This will work, val pattern = ".*prefix_([a-z]+).*".r, but it distinguishes between target and trash via lower/upper-case letters. Whatever determines real target data from trash data will determine the real regex pattern.
I am new to Scala and want to create a function to split Hello123 or Hello 123 into two strings as follows:
val string1 = 123
val string2 = Hello
What is the best way to do it, I have attempted to use regex matching \\d and \\D but I am not sure how to write the function fully.
Regards
You may replace with 0+ whitespaces (\s*+) that are preceded with letters and followed with digits:
var str = "Hello123"
val res = str.split("(?<=[a-zA-Z])\\s*+(?=\\d)")
println(res.deep.mkString(", ")) // => Hello, 123
See the online Scala demo
Pattern details:
(?<=[a-zA-Z]) - a positive lookbehind that only checks (but does not consume the matched text) if there is an ASCII letter before the current position in the string
\\s*+ - matches (consumes) zero or more spaces possessively, i.e.
(?=\\d) - this check is performed only once after the whitespaces - if any - were matched, and it requires a digit to appear right after the current position in the string.
Based on the given string I assume you have to match a string and a number with any number of spaces in between
here is the regex for that
([a-zA-Z]+)\\s*(\\d+)
Now create a regex object using .r
"([a-zA-Z]+)\\s*(\\d+)".r
Scala REPL
scala> val regex = "([a-zA-Z]+)\\s*(\\d+)".r
scala> val regex(a, b) = "hello 123"
a: String = "hello"
b: String = "123"
scala> val regex(a, b) = "hello123"
a: String = "hello"
b: String = "123"
Function to handle pattern matching safely
pattern match with extractors
str match {
case regex(a, b) => Some(a -> b.toInt)
case _ => None
}
Here is the function which does Regex with Pattern matching
def matchStr(str: String): Option[(String, Int)] = {
val regex = "([a-zA-Z]+)\\s*(\\d+)".r
str match {
case regex(a, b) => Some(a -> b.toInt)
case _ => None
}
}
Scala REPL
scala> def matchStr(str: String): Option[(String, Int)] = {
val regex = "([a-zA-Z]+)\\s*(\\d+)".r
str match {
case regex(a, b) => Some(a -> b.toInt)
case _ => None
}
}
defined function matchStr
scala> matchStr("Hello123")
res41: Option[(String, Int)] = Some(("Hello", 123))
scala> matchStr("Hello 123")
res42: Option[(String, Int)] = Some(("Hello", 123))
I have a string like this:
val str = "3.2.1"
And I want to do some manipulations based on it.
I will share also what I want to do and it will be nice if you can share your suggestions:
im doing automation for some website, and based on this string I need to do some actions.
So:
the first digit - I will need to choose by value: value="str[0]"
the second digit - I will need to choose by value: value="str[0]+"."+str[1]"
the third digit - I will need to choose by value: value="str[0]+"."+str[1]+"."+str[2]"
as you can see the second field i need to choose is the name firstdigit.seconddigit and the third field is firstdigit.seconddigit.thirddigit
You can use pattern matching for this.
First create regex:
# val pattern = """(\d+)\.(\d+)\.(\d+)""".r
pattern: util.matching.Regex = (\d+)\.(\d+)\.(\d+)
then you can use it to pattern match:
# "3.4.342" match { case pattern(a, b, c) => println(a, b, c) }
(3,4,342)
if you don't need all numbers you can for example do this
"1.2.0" match { case pattern(a, _, _) => println(a) }
1
if you want to for example to take just first two numbers you can do
# val twoNumbers = "1.2.0" match { case pattern(a, b, _) => s"$a.$b" }
twoNumbers: String = "1.2"
Can only add to #Lukasz's answer one more variant with the values extration:
# val pattern = """(\d+)\.(\d+)\.(\d+)""".r
pattern: scala.util.matching.Regex = (\d+)\.(\d+)\.(\d+)
# val pattern(firstdigit, seconddigit, thirddigit) = "3.2.1"
firstdigit: String = "3"
seconddigit: String = "2"
thirddigit: String = "1"
This way all the values can be treated as regular vals further in the code.
val str="vaquar.khan"
val strArray=str.split("\\.")
strArray.foreach(println)
Try the following:
scala> "3.2.1".split(".")
res0: Array[java.lang.String] = Array(string1, string2, string3)
This one:
object Splitter {
def splitAndAccumulate(string: String) = {
val s = string.split("\\.")
s.tail.scanLeft(s.head){ case (acc, elem) =>
acc + "." + elem
}
}
}
passes this test:
test("Simple"){
val t = Splitter.splitAndAccumulate("1.2.3")
val answers = Seq("1", "1.2", "1.2.3")
t.zip(answers).foreach{ case (l, r) =>
assert(l == r)
}
}
I have a list of words as a list an I would like to extract words that are maybe of lengths between 5 and 10, I am using the following code but doesn't seem to work. Also i can use only val and not var.
val sentence = args(0)
val words = sentence.split(" ")
val fullsort = words.sortBy(w => w.length -> w)
val med = fullsort.map(x => if(x.length>3 && x.length<11) x)
val sentence = args(0)
val words = sentence.split(" ")
val results = words.filter(word => word.length >= 5 && word.length <= 10)
Try this
val sentence = args(0)
val words = sentence.split(" ")
val fullsort = words.sortBy(w => w.length -> w)
val med = fullsort collect {case x:String if (x.length >= 5 && x.length <= 10) => x}
Another alternative is to let a regex do more of the work for you:
val wordLimitRE = "\\b\\w{5,10}\\b".r
val wordIterator = wordLimitRE.findAllMatchIn(sentence).map {_.toString}
This particular regex starts with a word boundary pattern \b then a range limited match for a number of word characters \w{lower, upper} then finally another word boundary pattern \b
The method findAllMatchIn returns an Iterator[Regex.Match] for each match (matches don't overlap because of the word boundary patterns). The map {_.toString} returns an Iterator[String]