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Imagine a text file where each csv record may have different numbers of fields. The task is to write code to output how many fields there are in each record of the file. You can assume there is no header line in the file and can read in from a file or standard input, as you choose.

You can assume a version of rfc4180 for the csv rules which I will explain below for the definition of each line of the file. Here is a lightly edited version of the relevant part of the spec:

Definition of the CSV Format

  1. Each record is located on a separate line, delimited by a line break (CRLF). For example:

    aaa,bbb,ccc CRLF
    

zzz,yyy,xxx CRLF

  1. The last record in the file may or may not have an ending line break. For example:

    aaa,bbb,ccc CRLF
    

zzz,yyy,xxx

(Rule 3. does not apply in this challenge)

  1. Within each record, there may be one or more fields, separated by commas. Spaces are considered part of a field and should not be ignored.

  2. Each field may or may not be enclosed in double quotes. If fields are not enclosed with double quotes, then double quotes may not appear inside the fields. For example:

    "aaa","bbb","ccc" CRLF
    

zzz,yyy,xxx

  1. Fields containing line breaks (CRLF), double quotes, and commas should be enclosed in double-quotes. For example:

    "aaa","b CRLF
    

bb","ccc" CRLF zzz,yyy,xxx

  1. If double-quotes are used to enclose fields, then a double-quote appearing inside a field must be escaped by preceding it with another double quote. For example:

    "aaa","b""bb","ccc"

Example

Input:

,"Hello, World!"
"aaa","b""bb","ccc"
zzz,yyy,
"aaa","b 
bb","ccc","fish",""

Should give the output:

2, 3, 3, 5

Your can give the output values in any way you find most convenient.

Libraries

You can use any library you like.


Awesome answers so far but we are missing a command line/bash answer which would be particularly cool.

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10 Answers 10

5
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Stax, 19 12 bytes

èJ§3‼}vAà○L>

Run and debug it

Unpacked, ungolfed, and commented, it looks like this.

_'"/    split *all* of standard input by double quote characters
2::     keep only the even numbered elements
|j      split on newlines (implicitly concatenates array of "strings")
m       for each line, execute the rest of the program and output
  ',#^  count the number of commas occurring as substrings, and increment

Run this one

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2
  • 1
    \$\begingroup\$ How does it work? \$\endgroup\$
    – user9207
    Jun 10, 2018 at 10:03
  • 1
    \$\begingroup\$ @Anush: I've added some more information. \$\endgroup\$
    – recursive
    Jun 10, 2018 at 15:27
4
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R, 40 bytes

(x=count.fields(stdin(),","))[!is.na(x)]

Try it online!

Per the documentation of count.fields, fields with line breaks get a field count of NA for the initial line, so we filter them out.

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3
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JavaScript (ES2018), 42 59 bytes

s=>s.replace(/".+?"/sg).split`\n`.map(c=>c.split`,`.length)

f=
s=>s.replace(/".+?"/sg).split`\n`.map(c=>c.split`,`.length)

console.log(f(
`,"Hello, World!"
"aaa","b""bb","ccc"
zzz,yyy,
"aaa","b 
bb","ccc","fish",""`))

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4
  • \$\begingroup\$ Technically this is ES2018 due to the s flag on the regex. Not that it matters that much ;-) And nice use of it, btw! \$\endgroup\$ Jun 10, 2018 at 2:07
  • 2
    \$\begingroup\$ This function only appears to work on one record at a time. I think the problem description requires handling an entire file of multiple records. \$\endgroup\$
    – recursive
    Jun 10, 2018 at 3:46
  • \$\begingroup\$ @ETHproductions, good point, will update. \$\endgroup\$ Jun 10, 2018 at 11:07
  • \$\begingroup\$ @recursive, you're right, I misunderstood the inputs. Now updated, at the loss of many many bytes. \$\endgroup\$ Jun 10, 2018 at 12:17
3
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Jelly, 12 bytes

ṣ”"m2FỴ=”,§‘

A port of recursive's Stax answer - go give credit!

Try it online!

How?

ṣ”"m2FỴ=”,§‘ - Link: list of characters, V
 ”"          - a double quote character = '"'
ṣ            - split (V) at ('"')
   m2        - modulo slice with two (1st, 3rd, 5th, ... elements of that)
     F       - flatten list of lists to a list
      Ỵ      - split at newlines
        ”,   - comma character = ','
       =     - equal? (vectorises)
          §  - sum each
           ‘ - increment (vectorises)
             - (as a full program implicit print)

Maybe you prefer ṣ”"m2ẎỴċ€”,‘ - is tighten and ċ€ counts the commas in each.

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2
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Python, 63 bytes

import csv
def f(s):return map(len,csv.reader(s.split("\n"))

Returns the output in an iterable map object.

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1
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    \$\begingroup\$ Using a lambda function you can get this down to 54 bytes \$\endgroup\$
    – ovs
    Jun 9, 2018 at 22:38
2
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Wolfram Language (Mathematica), 30 bytes

Length/@ImportString[#,"CSV"]&

Try it online!

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2
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Perl 5.10.0, 55 53 bytes

$_=shift;s/"(""|[^"])*"//g;s/^.*$/1+$&=~y:,::/gem;say

Try it online!

Explanation:

$_=shift;          # first command-line arg
s/"(""|[^"])*"//g; # remove quoted fields
s/^.*$/            # replace each line       
  1+$&=~y:,::      # by the number of commas plus 1
/gem;
say                # print
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2
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Java 10, 101 bytes

s->{for(var p:s.replaceAll("\"[^\"]*\"","x").split("\n"))System.out.println(p.split(",",-1).length);}

Try it online.

Explanation:

s->{                                    // Method with String parameter and no return-type
  for(var p:s.replaceAll("\"[^\"]*\"","x") 
                                        //  Replace all words within quotes with an "x"
             .split("\n"))              //  Then split by new-line and loop over them:
    System.out.println(p.split(",",-1)  //   Split the item by comma's
                        .length);}      //   And print the length of this array
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1
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Jelly, 17 bytes

=”"ÄḂżṣ⁷Ż¤ṣ€0,”,Ẉ

Try it online!

-1 thanks to Jonathan Allan. duh duh duh...

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0
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POSIX shell (ShellShoccar-jpn/Parsrs + usp-engineers-community/Open-usp-tukubai), 19 bytes

Dependencies are

parsrc.sh|count 1 1

Output format

For each line, the following line is output:

<row number> <number of columns>

How it works

parsrc.sh is a parser for CSV who converts such text into list of cells and their value. Open-usp-tukubai's count takes a range of field number from parameters and space-separated values to count in such range to summarize. Here are some comments:

# raw CSV
parsrc.sh |
# 1: row number 2: column number 3: value where LFs are represented as "\n" while real backslashes as "\\"
count 1 1
# 1: row number 2: number of columns in the row

Example run on Termux

Because Termux is not a completely POSIX-compatible so command -p getconf PATH fails, I am dropping the boilerplate to set PATH environment variable so the shell calls completely POSIX-compatible utilities first. Also because I am lazy to prepare Python 2, I am doing with COMMANDS.SH/count.

Example run on Termux but had some modification

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