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Date: Thu, 06 Feb 2014 00:34:57 +0000
From: MRAB <python@mrabarnett.plus.com>
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Subject: Re: parse a csv file into a text file
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On 2014-02-06 00:10, 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])
>
> [/code]
>
> This is not working for me, 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.
>
% is an operator. When used with a format string on its left, its
arguments go on its right. In the general case, those arguments should
be put in a tuple, although if there's only one argument and it's not a
tuple, you can write just that argument:

     f.write("%s %s" % (line[1], line[5]))

> 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).
>
Use find to tell you the index of the "(" (if there isn't one then
it'll return -1) and then slice the string to get the part preceding it.

Another way is to use the "partition" method.

Also, have a look at the "strip"/"lstrip"/"rstrip" methods.

> 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
>