I have the following pattern that I could parse using pandas in Python, but struggle with translating the code into Scala.

grade string_column    
 85   (str:ann smith,14)(str:frank chase,15)
 86   (str:john foo,15)(str:al more,14)

In python I used:

df.set_index('grade')['string_column']\
.str.extractall(r'\((str:[^,] ),(\d )\)')\
.droplevel(1)

with the output:

 grade       0                1
 85      str:ann smith       14
 85      str:frank chase     15
 86      str:john foo        15
 86      str:al more         14

In Scala I tried to duplicate the approach, but it's failing:

import scala.util.matching.Regex

val pattern = new Regex("((str:[^,] ),(\d )\)")
val str = "(str:ann smith,14)(str:frank chase,15)"

println(pattern findAllIn(str)).mkString(","))

CodePudding user response：

There are a few notes about the code:

• There is an unmatched parenthesis for a group, but that one should be escaped
• The backslashes should be double escaped
• In the println you don't have to use all the parenthesis and the dot
• findAllIn returns a MatchIterator, and looping those will expose a matched string. Joining those matched strings with a comma, will in this case give back the same string again.

For example

import scala.util.matching.Regex

val pattern = new Regex("\\((str:[^,] ),(\\d )\\)")
val str = "(str:ann smith,14)(str:frank chase,15)"

println(pattern findAllIn str mkString ",")

Output

(str:ann smith,14),(str:frank chase,15)

But if you want to print out the group 1 and group 2 values, you can use findAllMatchIn that returns a collection of Regex Matches:

import scala.util.matching.Regex

val pattern = new Regex("\\((str:[^,] ),(\\d )\\)")
val str = "(str:ann smith,14)(str:frank chase,15)"
pattern findAllMatchIn str foreach(m => {
    println(m.group(1))
    println(m.group(2))
  }
)

Output

str:ann smith
14
str:frank chase
15

CodePudding user response：

In Python, Series.str.extractall only returns captured substrings. In Scala, findAllIn returns the matched values if you do not query its matchData property that in its turn contains a subgroups property.

So, to get the captures only in Scala, you need to use

val pattern = """\((str:[^,()] ),(\d )\)""".r
val str = "(str:ann smith,14)(str:frank chase,15)"
(pattern findAllIn str).matchData foreach {
    m => println(m.subgroups.mkString(","))
}

Output:

str:ann smith,14
str:frank chase,15

See the Scala online demo.

Here, m.subgroups accesses all subgroups (captures) of each match (m).

Also, note you do not need to double backslashes in triple-quoted string literals. \((str:[^,()] ),(\d )\) matches

• \( - a ( char
• (str:[^,()] ) - Group 1: str: and one or more chars other than ,, ( and )
• , - a comma
• (\d ) - Group 2: one or more digits
• \) - a ) char.

If you just want to get all matches without captures, you can use

val pattern = """\((str:[^,] ),(\d )\)""".r
println((pattern findAllIn str).matchData.mkString(","))

Output:

(str:ann smith,14),(str:frank chase,15)

See the online demo.