CSV Reader

[Mike P]

Hi All,

I want to read in a CSV file, but then write out a new CSV file from a
given line..

I'm using the CSV reader and have the the line where i want to start
writing the new file from begins with
"Transactio n ID",

i thought it should be something along the lines of below.. obvioulsy
this doesn't work but any help would be great.

import csv
f = file(working_CS V, 'rb')
new_data = 0 # a counter to find where the line starts with
"Transactio n ID"
reader = csv.reader(f)
for data in reader:
read data file

write new CSV

Cheers

Mike

[Larry Bates]

Re: CSV Reader

Mike P wrote:

Hi All,
>
I want to read in a CSV file, but then write out a new CSV file from a
given line..
>
I'm using the CSV reader and have the the line where i want to start
writing the new file from begins with
"Transactio n ID",
>
i thought it should be something along the lines of below.. obvioulsy
this doesn't work but any help would be great.
>
import csv
f = file(working_CS V, 'rb')
new_data = 0 # a counter to find where the line starts with
"Transactio n ID"
reader = csv.reader(f)
for data in reader:
read data file
>
write new CSV
>
Cheers
>
Mike
>

What part "obviously" doesn't work? Try something, post any tracebacks and we
will try to help. Don't ask others to write your code for you without actually
trying it yourself. It appears you are on the right track.

-Larry

[Mike P]

Re: CSV Reader

Cheers for the help, the second way looked to be the best in the end,
and thanks for the boolean idea

Mike



working_CSV = "//filer/common/technical/Research/E2C/Template_CSV/
DFAExposureToCo nversionQueryTo ol.csv"

save_file = open("//filer/common/technical/Research/E2C/Template_CSV/
CSV_Data2.csv", "w")

CSV_Data = open(working_CS V)
data = CSV_Data.readli nes()
flag=False
for record in data:
if record.startswi th('"Transactio n ID"'):
flag=True
if flag:
save_file.write (record)
save_file.close ()

[Gabriel Genellina]

Re: CSV Reader

En Mon, 11 Feb 2008 14:41:54 -0200, Mike P
<michael.pearma in@tangozebra.c omescribi�:

CSV_Data = open(working_CS V)
data = CSV_Data.readli nes()
flag=False
for record in data:
if record.startswi th('"Transactio n ID"'):
[...]

Files are already iterable by lines. There is no need to use readlines(),
and you can avoid the already menctioned potential slowdown problem. Just
remove the data=CSV_data.r eadlines() line, and change that for statement
to be:
for record in CSV_Data:

Reading the style guide may be beneficial:

http://www.python.org/dev/peps/pep-0008/

--
Gabriel Genellina

[Mike P]

Re: CSV Reader

I did just try to post, but it doesn't look like it has appeared?

I've used your advice Andrew and tried to use the CSV module, but now
it doesn't seem to pick up the startswith command?
Is this because of the way the CSV module is reading the data in?
I've looked into the module description but i can't find anything that
i hould be using?

Can anyone offer an advice?

Cheers again

Mike

working_CSV = "//filer/common/technical/Research/E2C/Template_CSV/
DFAExposureToCo nversionQueryTo ol.csv"

save_file = "//filer/common/technical/Research/E2C/Template_CSV/
CSV_Data2.csv"

start_line=Fals e
import csv
reader = csv.reader(open (working_CSV, "rb"))
writer = csv.writer(open (save_file, "wb"))
for row in reader:
if not start_line and record.startswi th("'Transactio n ID'"):
start_line=True
if start_line:
print row
writer.writerow s(rows)
#writer.close()

[Mike P]

Re: CSV Reader

just saw i needed to change record.startswi th to row.startswith
but i get hte following traceback error

Traceback (most recent call last):
File "C:\Python25\Li b\site-packages\python win\pywin\frame work
\scriptutils.py ", line 310, in RunScript
exec codeObject in __main__.__dict __
File "Y:\technical\R esearch\E2C\Tem plate_CSV\impor t CSV test.py",
line 10, in <module>
if not start_line and row.startswith( 'Transaction ID'):
AttributeError: 'list' object has no attribute 'startswith'

[Chris]

Re: CSV Reader

On Feb 12, 12:21 pm, Mike P <michael.pearm. ..@tangozebra.c omwrote:

I did just try to post, but it doesn't look like it has appeared?
>
I've used your advice Andrew and tried to use the CSV module, but now
it doesn't seem to pick up the startswith command?
Is this because of the way the CSV module is reading the data in?
I've looked into the module description but i can't find anything that
i hould be using?
>
Can anyone offer an advice?
>
Cheers again
>
Mike
>
working_CSV = "//filer/common/technical/Research/E2C/Template_CSV/
DFAExposureToCo nversionQueryTo ol.csv"
>
save_file = "//filer/common/technical/Research/E2C/Template_CSV/
CSV_Data2.csv"
>
start_line=Fals e
import csv
reader = csv.reader(open (working_CSV, "rb"))
writer = csv.writer(open (save_file, "wb"))
for row in reader:
if not start_line and record.startswi th("'Transactio n ID'"):
start_line=True
if start_line:
print row
writer.writerow s(rows)
#writer.close()

record won't have an attribute 'startswith' because record is a list
and startswith is a function of a string.
Also, your code isn't exactly clear on what you want to do, if it is
just "Find the first occurence of Transaction ID and pump the file
from then onwards into a new file" why not

output = open('output_fi le.csv','wb')
start_line = False
for each_line in open('input_fil e.csv','rb'):
if not start_line and each_line.start swith("'Transac tion ID'"):
start_line = True
if start_line:
output.write( each_line )
output.close()

also, if you need a line number for any purposes, take a look at
enumerate() and with that it will return a counter and your data, for
eg. 'for (line_num, each_line) in enumerate(input _file):'. Counting
starts @ zero though so you would need to add 1.

[Mike P]

Re: CSV Reader

Hi Chris that's exactley what i wanted to do,

Many thanks

[Mike P]

Re: CSV Reader

I was just trying to do it with the CSV module

[Gabriel Genellina]

Re: CSV Reader

En Tue, 12 Feb 2008 08:37:13 -0200, Mike P
<michael.pearma in@tangozebra.c omescribi�:

just saw i needed to change record.startswi th to row.startswith
but i get hte following traceback error
>
Traceback (most recent call last):
File "C:\Python25\Li b\site-packages\python win\pywin\frame work
\scriptutils.py ", line 310, in RunScript
exec codeObject in __main__.__dict __
File "Y:\technical\R esearch\E2C\Tem plate_CSV\impor t CSV test.py",
line 10, in <module>
if not start_line and row.startswith( 'Transaction ID'):
AttributeError: 'list' object has no attribute 'startswith'

The csv reader doesn't return complete lines, but a list of fields for
each line. If you want to check the first field, use:

if not start_line and row[0].startswith('Tr ansaction ID'):

--
Gabriel Genellina