Re: [Tutor] newb help reading lines from csv
Dear Rob,
This caught me out as well for a long time.
As I understand it, csv.reader is a file-reader, which iterates ONCE
over the file. There may be more elegant solutions, but I do:
import csv
ifile = open('test.csv', "r")
reader = csv.reader(ifile)
inData = []
for row in reader:
inData.append[row]
ifile.close()
you can now loop through inData to your heart's desire.
HTH,
Matt
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Re: [Tutor] newb help reading lines from csv
Dewhirst, Rob wrote: > Thanks Matt and Lazlo. I knew I must have been missing some counter > not being reset. Both of those options work fine. > > You want to do ifile.seek(0) not reader.seek(0) at least from my testing. > > > On Mon, Oct 22, 2012 at 2:27 PM, Matt Williams wrote: [snip] Please do not top post. This list's etiquette is to write your response in-line or below the quoted text. Thank you. Ramit Prasad This email is confidential and subject to important disclaimers and conditions including on offers for the purchase or sale of securities, accuracy and completeness of information, viruses, confidentiality, legal privilege, and legal entity disclaimers, available at http://www.jpmorgan.com/pages/disclosures/email. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] newb help reading lines from csv
On Mon, Oct 22, 2012 at 3:35 PM, Dewhirst, Rob wrote:
>
>> import csv
>> ifile = open('test.csv', "r")
>> reader = csv.reader(ifile)
>> inData = []
>> for row in reader:
>> inData.append[row]
>> ifile.close()
>>
>> you can now loop through inData to your heart's desire.
Alternatively:
import csv
with open('test.csv', 'rb') as ifile:
inData = list(csv.reader(ifile))
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Re: [Tutor] newb help reading lines from csv
On Mon, Oct 22, 2012 at 3:35 PM, Dewhirst, Rob wrote:
> Thanks Matt and Lazlo. I knew I must have been missing some counter
> not being reset. Both of those options work fine.
>
> You want to do ifile.seek(0) not reader.seek(0) at least from my testing.
>
>
> On Mon, Oct 22, 2012 at 2:27 PM, Matt Williams wrote:
>> Dear Rob,
>>
>> This caught me out as well for a long time.
>>
>> As I understand it, csv.reader is a file-reader, which iterates ONCE over
>> the file. There may be more elegant solutions, but I do:
>>
>>
>> import csv
>> ifile = open('test.csv', "r")
>> reader = csv.reader(ifile)
>> inData = []
>> for row in reader:
>> inData.append[row]
>> ifile.close()
>>
>> you can now loop through inData to your heart's desire.
>>
>> HTH,
>>
>> Matt
If you want to learn more about python iterators this is a good place
to start: http://docs.python.org/howto/functional.html#iterators
or google python iterators. They are pretty cool to understand
--
Joel Goldstick
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Re: [Tutor] newb help reading lines from csv
On Mon, Oct 22, 2012 at 3:28 PM, LZAntal wrote:
> On Oct 22, 2012, at 12:20 PM, "Dewhirst, Rob" wrote:
>
>> import csv
>> ifile = open('test.csv', "r")
>> reader = csv.reader(ifile)
>
> I believe csv module uses iterator so you need to run reader.seek(0) between
> the for loops
You have to reset the file iterator with ifile.seek(0). You might also
want a new reader if you care about the line_num attribute, but
otherwise you can keep using the same reader.
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Re: [Tutor] newb help reading lines from csv
Thanks Matt and Lazlo. I knew I must have been missing some counter
not being reset. Both of those options work fine.
You want to do ifile.seek(0) not reader.seek(0) at least from my testing.
On Mon, Oct 22, 2012 at 2:27 PM, Matt Williams wrote:
> Dear Rob,
>
> This caught me out as well for a long time.
>
> As I understand it, csv.reader is a file-reader, which iterates ONCE over
> the file. There may be more elegant solutions, but I do:
>
>
> import csv
> ifile = open('test.csv', "r")
> reader = csv.reader(ifile)
> inData = []
> for row in reader:
> inData.append[row]
> ifile.close()
>
> you can now loop through inData to your heart's desire.
>
> HTH,
>
> Matt
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Re: [Tutor] newb help reading lines from csv
On Mon, Oct 22, 2012 at 3:20 PM, Dewhirst, Rob wrote:
> import csv
> ifile = open('test.csv', "r")
> reader = csv.reader(ifile)
> for row in reader:
> print row
> for row in reader:
> print row
> ifile.close()
>
> This is a simplified version of what I am trying to do - loop through
> a CSV file twice. Why does the second for loop not execute at all?
> The first one prints the rows of the file just fine.
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You need to close the file and re open to iterate again. You can't
reset the iterator back to the beginning without closing and
re-opening
--
Joel Goldstick
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Re: [Tutor] newb help reading lines from csv
Dewhirst, Rob wrote:
import csv
ifile = open('test.csv', "r")
reader = csv.reader(ifile)
for row in reader:
print row
for row in reader:
print row
ifile.close()
This is a simplified version of what I am trying to do - loop through
a CSV file twice. Why does the second for loop not execute at all?
The first one prints the rows of the file just fine.
The first pass also exhausts the input feed -- you'll need to rewind or
reposition the next line pointer to the start of the file and I suspect
the easiest way is to reopen the file.
Emile
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Re: [Tutor] newb help reading lines from csv
Hi,
On Oct 22, 2012, at 12:20 PM, "Dewhirst, Rob" wrote:
> import csv
> ifile = open('test.csv', "r")
> reader = csv.reader(ifile)
> for row in reader:
> print row
> for row in reader:
> print row
> ifile.close()
>
> This is a simplified version of what I am trying to do - loop through
> a CSV file twice. Why does the second for loop not execute at all?
> The first one prints the rows of the file just fine.
> _
I believe csv module uses iterator so you need to run reader.seek(0) between
the for loops
Laszlo
http://twitter.com/LZAntal
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[Tutor] newb help reading lines from csv
import csv
ifile = open('test.csv', "r")
reader = csv.reader(ifile)
for row in reader:
print row
for row in reader:
print row
ifile.close()
This is a simplified version of what I am trying to do - loop through
a CSV file twice. Why does the second for loop not execute at all?
The first one prints the rows of the file just fine.
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