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Given two lists of string elements list1 and list2:

list1 = {"stel", "segw", "ma7", "str1"};
list2 = {
   "agr: Agriculture, hunting, forestry, fishing", 
   "min: Mining and quarrying", "ma1: Food, beverages, tobacco", 
   "ma2: Textiles, textile products", 
   "ma3: Leather, leather products, footwear", 
   "ma4: Wood & products of wood and cork", 
   "ma5: Pulp, paper, paper products, printing, publishing", 
   "ma6: Coke, refined petroleum, nuclear fuel", 
   "ma7: Chemicals & chemical products", 
   "ma8: Rubber-plastics products", 
   "ma9: Other non-metallic mineral products", 
   "ma10: Manufacture of basic metals", 
   "ma11: Machinery-equipment n.e.c", 
   "ma12: Electrical equipment", 
   "ma13: Transport equipment", 
   "ma14: Manufacturing, nec; recycling",
   "segw: Electricity, gas, water supply",
   "scst: Construction", 
   "ma15: Sale-maintenance; repair-install. of mach. equip.", 
   "swhl: Wholesale trade, except motor vehicles", 
   "srtl: Retail trade, except of motor vehicles", 
   "shot: Hotels & restaurants", "str1: Inland transport", 
   "str2: Water transport", 
   "str3: Air transport", 
   "str4: Other supporting-transport act. of travel agencies", 
   "stel: Post & telecommunications", 
   "sfin: Financial intermediation", 
   "sest: Real estate activities", 
   "sbus: Renting of M&Eq and other business activities", 
   "sadm: Public adm.-defence;compulsory social security", 
   "sedu: Education", 
   "shlt: Human health-social work", 
   "soth: Other community, social & personal services"
         };

I want to use list1 as the key to select the names after : in list2. The selection should be in the order of list1 as follows:

answer = {
  "Post & telecommunications",
  "Electricity, gas, water supply", 
  "Chemicals & chemical products",
  "Inland transport"
};
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7 Answers 7

5
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Use StringSplit to split values in list2, then use KeyTake to extract the indices you want.

Values@KeyTake[(Rule @@@ (StringSplit[#, ": "] & /@ list2)), list1]
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(Association@(MapApply[Rule]@StringSplit[list2,":"]))/@list1

(* { Post & telecommunications, 
     Electricity, gas, water supply, 
     Chemicals & chemical products, 
     Inland transport}  *)
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1
  • 2
    $\begingroup$ Seems the most intuitive for me. $\endgroup$ Commented Sep 26, 2023 at 12:07
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Lookup[list1] @ MapApply[Rule] @ StringSplit[list2, ":"]

{" Post & telecommunications", " Electricity, gas, water supply", "
Chemicals & chemical products", " Inland transport"}

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1
  • $\begingroup$ very easy to understand (for me) and remember... $\endgroup$ Commented Sep 26, 2023 at 12:52
4
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StringCases[StringJoin[Riffle[list2, "\n"]], 
   RegularExpression[# <> ": (.+)"] -> "$1"] & /@ list1

{{"Post & telecommunications"}, {"Electricity, gas, water supply"},
{"Chemicals & chemical products"}, {"Inland transport"}}

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3
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My attempt using Select and StringStartsQ:

getDescriptions[code_List, descriptions_List] := 
Module[{order}, 
order = PositionIndex[code];
StringSplit[#, ": "][[2]] & /@ 
SortBy[Select[descriptions, StringStartsQ[#, Alternatives @@ code] &], 
order[First[StringSplit[#, ":"]]] &]]

Testing getDescriptions:

getDescriptions[list1, list2] === answer

(*True*)
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2
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A default clause is provided with the Lookup command, should you want to exploit it. Assuming:

list1 = {"stel", "segw", "ma7", "str1", "xyz"};
lut = Rule @@@ StringSplit[list2, ":"];
Lookup[lut, #, Framed@StringJoin[#, ":", "Not found"]] & /@ list1

enter image description here

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(*Make a rule list*)
ruleList = Rule @@@ (StringSplit[#, ":"] & /@ list2);

(*Apply rules to list1*)
answer = list1 /. ruleList;

(*Remove leading and trailing white spaces*)
answer = StringTrim /@ answer;
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