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parse a csv file into a text file

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  parse a csv file into a text file Zhen Zhang <zhen.zhang.uoft@gmail.com> - 2014-02-05 16:10 -0800
    Re: parse a csv file into a text file Asaf Las <roegltd@gmail.com> - 2014-02-05 16:17 -0800
      Re: parse a csv file into a text file Zhen Zhang <zhen.zhang.uoft@gmail.com> - 2014-02-05 23:56 -0800
    Re: parse a csv file into a text file Roy Smith <roy@panix.com> - 2014-02-05 19:33 -0500
      Re: parse a csv file into a text file Zhen Zhang <zhen.zhang.uoft@gmail.com> - 2014-02-05 23:52 -0800
        Re: parse a csv file into a text file Asaf Las <roegltd@gmail.com> - 2014-02-06 00:15 -0800
          Re: parse a csv file into a text file Asaf Las <roegltd@gmail.com> - 2014-02-06 00:48 -0800
        Re: parse a csv file into a text file MRAB <python@mrabarnett.plus.com> - 2014-02-06 13:16 +0000
          Re: parse a csv file into a text file Rustom Mody <rustompmody@gmail.com> - 2014-02-06 05:20 -0800
    Re: parse a csv file into a text file MRAB <python@mrabarnett.plus.com> - 2014-02-06 00:34 +0000
      Re: parse a csv file into a text file Zhen Zhang <zhen.zhang.uoft@gmail.com> - 2014-02-06 00:01 -0800
    Re: parse a csv file into a text file Tim Chase <python.list@tim.thechases.com> - 2014-02-05 18:46 -0600
      Re: parse a csv file into a text file Asaf Las <roegltd@gmail.com> - 2014-02-05 19:59 -0800
        Re: parse a csv file into a text file Tim Chase <python.list@tim.thechases.com> - 2014-02-05 22:09 -0600
          Re: parse a csv file into a text file Asaf Las <roegltd@gmail.com> - 2014-02-05 20:17 -0800
      Re: parse a csv file into a text file Zhen Zhang <zhen.zhang.uoft@gmail.com> - 2014-02-06 00:07 -0800
        Re: parse a csv file into a text file Tim Chase <python.list@tim.thechases.com> - 2014-02-06 12:49 -0600
    Re: parse a csv file into a text file Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-02-06 00:50 +0000
    Re:parse a csv file into a text file Dave Angel <davea@davea.name> - 2014-02-05 19:57 -0500
      Re: parse a csv file into a text file Zhen Zhang <zhen.zhang.uoft@gmail.com> - 2014-02-06 00:12 -0800
        Re: parse a csv file into a text file Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2014-02-06 10:49 +0200
        Re: parse a csv file into a text file Dave Angel <davea@davea.name> - 2014-02-06 06:35 -0500
        Re: parse a csv file into a text file Dave Angel <davea@davea.name> - 2014-02-06 06:53 -0500
    Re: parse a csv file into a text file Terry Reedy <tjreedy@udel.edu> - 2014-02-05 22:01 -0500
    Re: parse a csv file into a text file Neil Cerutti <neilc@norwich.edu> - 2014-02-06 14:02 +0000
    Re: parse a csv file into a text file Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-02-06 17:40 +0000
    Re: parse a csv file into a text file Tim Chase <python.list@tim.thechases.com> - 2014-02-06 11:51 -0600
    Re: parse a csv file into a text file Tim Golden <mail@timgolden.me.uk> - 2014-02-06 18:05 +0000
    Re: parse a csv file into a text file Neil Cerutti <neilc@norwich.edu> - 2014-02-06 18:34 +0000
    Re: parse a csv file into a text file Tim Chase <python.list@tim.thechases.com> - 2014-02-06 12:51 -0600

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#65523

Zhen Zhang writes:
...
> I am currently running python 2.7.
> 
> Yes, i thought there must be a print function in python like fprint
> in C++ that allows you to print into a file directly.
>
> But i google about "print string into text file" I got answers using
> f.write() instead. :)

Indeed. The first Python hit for me with that query was the tutorial
page on I/O in Python 2, and it does exactly that.
<http://docs.python.org/2/tutorial/inputoutput.html>

That page does refer to the spec of the print statement, where you can
find the way to redirect the output to a file, but you need to be able
to read formal syntax specifications like this:

print_stmt ::=  "print" ([expression ("," expression)* [","]]
                | ">>" expression [("," expression)+ [","]])

The relevant pattern is the second alternative, after the vertical
bar, which can be instantiated this way:

  print >> f, e0, e1

There is one object f with a .write method, and one or more
expressions whose values get written using f.write; the effect of an
optional comma at end is also specified there. Not tutorial-level.
<http://docs.python.org/2/reference/simple_stmts.html#print>

But I use the newer print function even if I have to use 2.7,
something like this:

  from __future__ import print_function
  f = open("test.txt", "w")
  print("hello?", "see me?", file=f)
  f.close()

It does a modest amount of formatting: the value of the keyword
argument sep is written between the values, and the value of end is
written at end.

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#65530

 Zhen Zhang <zhen.zhang.uoft@gmail.com> Wrote in message:
> 

> I am currently running python 2.7.
> 
> Yes, i thought there must be a print function in python like fprint in C++ that allows you to print into a file directly.
> But i google about "print string into text file" I got answers using f.write() instead. :)
> -- 
> 
> 
In python 2.x,
 
Instead of 
       f.write (a + " " + b)
you can use
       print >> f, a, b



-- 
DaveA

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#65531

 Dave Angel <davea@davea.name> Wrote in message:
>  Zhen Zhang <zhen.zhang.uoft@gmail.com> Wrote in message:
>> 
> 
>> I am currently running python 2.7.
>> 
>> Yes, i thought there must be a print function in python like fprint in C++ that allows you to print into a file directly.
>> But i google about "print string into text file" I got answers using f.write() instead. :)
>> -- 
>> 
Oops. Forgot the newline. 

> In python 2.x,
>  
> Instead of 
>        f.write (a + " " + b)
         f.write (a  + " " + b + "\n")
> you can use
>        print >> f, a, b
> 

print will add in the space and newline,  just as it does to
 sys.stdout.


-- 
DaveA

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#65505

On 2/5/2014 7:10 PM, Zhen Zhang wrote:
> Hi, every one.
>
> I am a second year EE student.
> I just started learning python for my project.
>
> I intend to parse a csv file with a format like
>
> 3520005,"Toronto (Ont.)",C  ,F,2503281,2481494,F,F,0.9,1040597,979330,630.1763,3972.4,1
> 2466023,"Montréal (Que.)",V  ,F,1620693,1583590,T,F,2.3,787060,743204,365.1303,4438.7,2
> 5915022,"Vancouver (B.C.)",CY ,F,578041,545671,F,F,5.9,273804,253212,114.7133,5039.0,8
> 3519038,"Richmond Hill (Ont.)",T  ,F,162704,132030,F,F,23.2,53028,51000,100.8917,1612.7,28
>
> into a text file like the following
>
> Toronto 2503281
> Montreal 1620693
> Vancouver 578041
>
> I am extracting the 1st and 5th column and save it into a text file.
>
> This is what i have so far.
>
>
> [code]
>
> import csv
> file = open('raw.csv')
> reader = csv.reader(file)
>
> f = open('NicelyDone.text','w')
>
> for line in reader:
>        f.write("%s %s"%line[1],%line[5])
   f.write("%s %s\n" % (line[1], line[5])) should do better.
>
> [/code]
>
> This is not working for me,

Always say how something is not working. If there is a traceback, cut 
and paste after reading it carefully.


  I was able to extract the data from the csv file as line[1],line[5]. 
(I am able to print it out)
> But I dont know how to write it to a .text file in the format i wanted.
>
> Also, I have to process the first column eg, "Toronto (Ont.)" into "Toronto".
> I am familiar with the function find(), I assume that i could extract Toronto out of Toronto(Ont.) using "(" as the stopping character,
> but based on my research , I have no idea how to use it and ask it to return me the string(Toronto).
>
> Here is my question:
> 1:What is the data format for line[1], if it is string how come f.write()does not work. if it is not string, how do i convert it to a string?
> 2:How do i extract the word Toronto out of Toronto(Ont) into a string form using find() or other methods.
>
> My thinking is that I could add those 2 string together like c=a+' ' +b, that would give me the format i wanted.
> So i can use f.write() to write into a file  ;)
>
> Sorry if my questions sounds too easy or stupid.
>
> Thanks ahead
>
> Zhen
>


-- 
Terry Jan Reedy

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#65539

On 2014-02-06, Zhen Zhang <zhen.zhang.uoft@gmail.com> wrote:
> Hi, every one.
>
> I am a second year EE student.
> I just started learning python for my project.
>
> I intend to parse a csv file with a format like 
>
> 3520005,"Toronto (Ont.)",C > ,F,2503281,2481494,F,F,0.9,1040597,979330,630.1763,3972.4,1
[...]
 into a text file like the following
>
> Toronto 2503281
[...]
> This is what i have so far.
>
>
> [code]
>
> import csv
> file = open('raw.csv')

You must open the file in binary mode, as that is what the csv
module expects in Python 2.7. newline handling can be enscrewed
if you forget.

file = open('raw.csv', 'b')

-- 
Neil Cerutti

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#65544

On 06/02/2014 14:02, Neil Cerutti wrote:
>
> You must open the file in binary mode, as that is what the csv
> module expects in Python 2.7. newline handling can be enscrewed
> if you forget.
>
> file = open('raw.csv', 'b')
>

I've never opened a file in binary mode to read with the csv module 
using any Python version.  Where does it state that you must do this?

-- 
My fellow Pythonistas, ask not what our language can do for you, ask 
what you can do for our language.

Mark Lawrence

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#65545

On 2014-02-06 17:40, Mark Lawrence wrote:
> On 06/02/2014 14:02, Neil Cerutti wrote:
> >
> > You must open the file in binary mode, as that is what the csv
> > module expects in Python 2.7. newline handling can be enscrewed
> > if you forget.
> >
> > file = open('raw.csv', 'b')
> >
> 
> I've never opened a file in binary mode to read with the csv module 
> using any Python version.  Where does it state that you must do
> this?

While the docs don't currently say anything about it, all the
examples at [1] use 'rb' or 'wb' when opening the file.  I've long
wondered about that.  Especially as I've passed non-file objects like
lists/iterators to the csv.reader/csv.DictReader and had them work
just fine (and would be a little perturbed if they broke).

-tkc

[1] http://docs.python.org/2/library/csv.html

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#65547

On 06/02/2014 17:40, Mark Lawrence wrote:
> On 06/02/2014 14:02, Neil Cerutti wrote:
>>
>> You must open the file in binary mode, as that is what the csv
>> module expects in Python 2.7. newline handling can be enscrewed
>> if you forget.
>>
>> file = open('raw.csv', 'b')
>>
>
> I've never opened a file in binary mode to read with the csv module
> using any Python version.  Where does it state that you must do this?
>

If you don't, you tend to get interleaved blank lines. (Presumably 
unless your .csv is using \n-only linefeeds).

TJG

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#65549

On 2014-02-06, Tim Chase <python.list@tim.thechases.com> wrote:
> On 2014-02-06 17:40, Mark Lawrence wrote:
>> On 06/02/2014 14:02, Neil Cerutti wrote:
>> >
>> > You must open the file in binary mode, as that is what the csv
>> > module expects in Python 2.7. newline handling can be enscrewed
>> > if you forget.
>> >
>> > file = open('raw.csv', 'b')
>> >
>> 
>> I've never opened a file in binary mode to read with the csv module 
>> using any Python version.  Where does it state that you must do
>> this?
>
> While the docs don't currently say anything about it, all the
> examples at [1] use 'rb' or 'wb' when opening the file.  I've
> long wondered about that.  Especially as I've passed non-file
> objects like lists/iterators to the csv.reader/csv.DictReader
> and had them work just fine (and would be a little perturbed if
> they broke).

They do actually mention it.

From: http://docs.python.org/2/library/csv.html

  csv.reader(csvfile, dialect='excel', **fmtparams)

  Return a reader object which will iterate over lines in the
  given csvfile. csvfile can be any object which supports the
  iterator protocol and returns a string each time its next()
  method is called — file objects and list objects are both
  suitable. If csvfile is a file object, it must be opened with
  the ‘b’ flag on platforms where that makes a difference. 

So it's stipulated only for file objects on systems where it
might make a difference.

-- 
Neil Cerutti

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#65551

On 2014-02-06 18:34, Neil Cerutti wrote:
> They do actually mention it.
> 
> From: http://docs.python.org/2/library/csv.html
> 
>   If csvfile is a file object, it must be opened with
>   the ‘b’ flag on platforms where that makes a difference. 
> 
> So it's stipulated only for file objects on systems where it
> might make a difference.

Ah, I *knew* I'd read that somewhere but my searches in firefox (for
"binary", "rb" and "wb") didn't manage to catch that particular
instance.  Thanks for disinterring that.

-tkc

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