csv format - Import vs ReadList CSV file with Currency Values

A testing file with the specified format can be downloaded from here

Let's read a few lines from this file

(recLines = ReadList[csvFileName, Record, 3]) // TableForm

SalesOrderID,ProductID,ProductName,OrderDate,ShipDate,Revenue
51217,779,Soft Cushion,5/7/2014,11/7/2014,"$2,400"
51217,788,Soft Cushion,5/7/2014,11/7/2014,"$2,400"

ls[[2]] // FullForm

"51217,779,Soft Cushion,5/7/2014,11/7/2014,\"$2,400\""

Had I used the Import I would have got

recData = Import[csvFileName];
recDate[[1;;3]]//TableForm

SalesOrderID    ProductID   ProductName OrderDate   ShipDate    Revenue
51217   779 Soft Cushion    5/7/2014    11/7/2014   2400
51217   788 Soft Cushion    5/7/2014    11/7/2014   2400


Head /@ csvData[[3]]
{Integer, Integer, String, String, String, Integer}

This is exactly the output I would like to get, but instead of using Import I want to use ReadList.

I have read various posts related to ReadList and this is the closest I have found to an answer that will use ReadList

rl = ReadList[csvFileName, Word, WordSeparators->{","}, RecordSeparators->{"\n"}, RecordLists->True]

rl[[1 ;; 3]] // TableForm

 SalesOrderID   ProductID   ProductName OrderDate   ShipDate    Revenue 

  51217 779     Soft Cushion    5/7/2014        11/7/2014       "$2     400"
  51217 788     Soft Cushion    5/7/2014        11/7/2014       "$2      400"

rl[[3]] // FullForm

List["51217","788","Soft Cushion","5/7/2014","11/7/2014","\"$2","400\""]

Head /@ rl[[3]]
{String, String, String, String, String, String, String}

Could you please continue this to a full answer or perhaps share a better solution with ReadList ? For example, is it possible to read and transform at the same time with ReadList, by specifying the header, i.e. types of the record items, and get exactly the same result as that of Import ?

I also have this challenge question for the experts of the language:

ReadList is a memory efficient and fast method of reading and parsing CSV files. But it cannot detect automatically the data types of the record items, something that Import does AUTOMAGICALLY. Wouldn't be possible to implement somehow a ReadList that can also detect the header format?

If not, suppose we do know what is the format of the records, and suppose it does not change. There are all these cryptic types and options of ReadList to assist you in getting the parsing of data items right. Can somebody explain me in the file I specified how I can use these types and options to achieve reading lists same way like Import function ?

Answer

As long as you are using ReadList to read in the entire file, and then acting on each line, you may as well just feed the result of ReadLine into ImportString.

test = ImportString[
    StringJoin[
     Riffle[ReadList["shoes_revenue.csv", String], "\n"]
     ],

    "CSV"]; // AbsoluteTiming
(*{2.7918, Null}*)

which is marginally faster than this answer

conv = {ToExpression@#[[1]], 
    ToExpression@#[[2]], #[[3]], #[[4]], #[[5]], 
    ToExpression@StringTake[StringJoin@#[[6 ;;]], {3, -2}]} &;
(wrdlst = 
   conv /@ (ReadList["shoes_revenue.csv", Word, 
       WordSeparators -> {","}, RecordSeparators -> {"\n"}, 

       RecordLists -> True])[[2 ;;]];
  PrependTo[wrdlst, 
   Flatten@StringSplit[ReadList["shoes_revenue.csv", Record, 1], ","]];
  ) // AbsoluteTiming
(* {3.00567, Null} *)