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Seperating CSV rows into new, seperate files

P: n/a
Hi,
I've searched the group and need more information and guidance on this
issue I need to resolve next week. I work for the local school system
and I am working on a way to parse a CSV file of class lists from MS
Excel. It is a ~2MB file with all teachers and all their classes in
it. I thought I would use Python to do this since many people I know
tell me how great it is. The real sticking point is there are
duplicates of each teacher's classes embedded in the file (don't ask
why). I want to break up the source file into the seperate class
files without duplication and use the teachers name, coursecode and
section in the filename.

Example Data:
Last Name First Name Grade Period Teacher Name
SMITH JOHN 8 1 JONES SALLY

Student ID Course Code Course Title
12345678 1234 ALGEBRA I

Course Section Session
1 0
The course code and section number are the same in the duplicate
classes. The difference is that the session number changes. I'm
thinking that I will need to somehow iterate through the lines and
break the class when the course code changes and/or section change
(course codes can be the same but section numbers change with each
class). Then I have to monitor the session number to see if there is
a duplicate course code and section but a different session number
would indicate that the class is a duplicate. Essentially, the session
number will be 0, 1, or 2 for a total of three lists of the same
class. Hopefully that makes sense. Again don't ask why the data is
like this.

My humble attempts have not been very successful. I've been trying
the csv modules to read the file but I am not sure how to procede
after that.

Any guidance is greatly appreciated.
Jul 18 '05 #1
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5 Replies


P: n/a
TonyB wrote:
I've searched the group and need more information and guidance on this
issue I need to resolve next week. I work for the local school system
and I am working on a way to parse a CSV file of class lists from MS
Excel. It is a ~2MB file with all teachers and all their classes in
it. I thought I would use Python to do this since many people I know
tell me how great it is. The real sticking point is there are
duplicates of each teacher's classes embedded in the file (don't ask
why). I want to break up the source file into the seperate class
files without duplication and use the teachers name, coursecode and
section in the filename.

Example Data:
Last Name First Name Grade Period Teacher Name
SMITH JOHN 8 1 JONES SALLY

Student ID Course Code Course Title
12345678 1234 ALGEBRA I

Course Section Session
1 0
The course code and section number are the same in the duplicate
classes. The difference is that the session number changes. I'm
thinking that I will need to somehow iterate through the lines and
break the class when the course code changes and/or section change
(course codes can be the same but section numbers change with each
class). Then I have to monitor the session number to see if there is
a duplicate course code and section but a different session number
would indicate that the class is a duplicate. Essentially, the session
number will be 0, 1, or 2 for a total of three lists of the same
class. Hopefully that makes sense. Again don't ask why the data is
like this.

My humble attempts have not been very successful. I've been trying
the csv modules to read the file but I am not sure how to procede
after that.

Any guidance is greatly appreciated.


From the above I think you can use the (student id, course code, course
section) tuple as the unique key when reading the data via the cvs module
into a dictionary instead of a list. (For larger data you would need a
database - the humble MS Access could have saved you from the trouble with
duplicates in the first place, btw.)

#untested
STUDENT_ID = 5
COURSE_CODE = 6
COURSE_SECTION = 8
data = {}
for row in csv.reader(instream):
# you could do more processing here,
# e. g. with nested course/student
# dictionaries, but let's keep it simple
data[row[STUDENT_ID], row[COURSE_CODE], row[COURSE_SECTION]] = row

Subsequent sessions will then just overwrite data already in the dictionary.
Note that you are throwing away some information as I am pretty sure (don't
ask why :-) that the duplicates will not be completely identical.

You can split this raw data into classes like so:

#untested
klasses = {}
for row in data.values():
key = row[COURSE_CODE], row[COURSE_SECTION]
if key in klasses:
klasses[key].append(row)
else:
klasses[key] = [row]

If you feel comfortable with (Python) classes you can make the dictionary
values instances of a Row class that lets you access attributes by name, e.
g. row.studentID instead of row[STUDENT_ID].

If these hints aren't sufficient to get you started it would help if you
showed the code you already have to avoid duplicate effort.

Peter

PS: Who am I to talk about orthography, but it's "separate".
Jul 18 '05 #2

P: n/a
Hi TobyB,
Hi,
I've searched the group and need more information and guidance on this
issue I need to resolve next week. I work for the local school system
and I am working on a way to parse a CSV file of class lists from MS
Excel. It is a ~2MB file with all teachers and all their classes in
it. I thought I would use Python to do this since many people I know
tell me how great it is.
Pyhton is a good choice for treating texts.
The real sticking point is there are
duplicates of each teacher's classes embedded in the file (don't ask
why). I want to break up the source file into the seperate class
files without duplication and use the teachers name, coursecode and
section in the filename.

Example Data:
Last Name First Name Grade Period Teacher Name
SMITH JOHN 8 1 JONES SALLY

Student ID Course Code Course Title
12345678 1234 ALGEBRA I

Course Section Session
1 0
The course code and section number are the same in the duplicate
classes. The difference is that the session number changes. I'm
thinking that I will need to somehow iterate through the lines and
break the class when the course code changes and/or section change
(course codes can be the same but section numbers change with each
class). Then I have to monitor the session number to see if there is
a duplicate course code and section but a different session number
would indicate that the class is a duplicate. Essentially, the session
number will be 0, 1, or 2 for a total of three lists of the same
class. Hopefully that makes sense. Again don't ask why the data is
like this.

My humble attempts have not been very successful. I've been trying
the csv modules to read the file but I am not sure how to procede
after that.

Any guidance is greatly appreciated.


Use Python lists and dictionaries.

Best regards,

Maik Röder

Jul 18 '05 #3

P: n/a
Hi TobyB,
Hi,
I've searched the group and need more information and guidance on this
issue I need to resolve next week. I work for the local school system
and I am working on a way to parse a CSV file of class lists from MS
Excel. It is a ~2MB file with all teachers and all their classes in
it. I thought I would use Python to do this since many people I know
tell me how great it is.
Pyhton is a good choice for treating texts.
The real sticking point is there are
duplicates of each teacher's classes embedded in the file (don't ask
why). I want to break up the source file into the seperate class
files without duplication and use the teachers name, coursecode and
section in the filename.

Example Data:
Last Name First Name Grade Period Teacher Name
SMITH JOHN 8 1 JONES SALLY

Student ID Course Code Course Title
12345678 1234 ALGEBRA I

Course Section Session
1 0
The course code and section number are the same in the duplicate
classes. The difference is that the session number changes. I'm
thinking that I will need to somehow iterate through the lines and
break the class when the course code changes and/or section change
(course codes can be the same but section numbers change with each
class). Then I have to monitor the session number to see if there is
a duplicate course code and section but a different session number
would indicate that the class is a duplicate. Essentially, the session
number will be 0, 1, or 2 for a total of three lists of the same
class. Hopefully that makes sense. Again don't ask why the data is
like this.

My humble attempts have not been very successful. I've been trying
the csv modules to read the file but I am not sure how to procede
after that.

Any guidance is greatly appreciated.


Use Python lists and dictionaries.

Best regards,

Maik Röder
Jul 18 '05 #4

P: n/a
OK,
With some off post help I was able to come up with this little ditty
of a script but it still has one more problem. When I run the script
it creates new files for each specific class. While talking through
the logic with a friend, I realized that the gradebook software that
will import the list will ignore duplicate rows. Not the best
solution but I need it to work this week. In any case, it appears
that the new files have some sort of additional line terminator that
creates a blank row in the outputted file making the importing of the
list impossible. This is based on the fact that when I try to open
the new files in MS Excel, they have blank rows after each row of
data. If I open them in a text editor such as Notepad, they look
identical to the source file (which can be imported to the gradbook
software).

Is there a way to SEE the newline terminators?
How can I use the csv.writer() to make sure there are no extra lines?

My Script:
**************************************
import csv

TEACHER_NAME = 4
COURSE_TITLE = 9
COURSE_NUMBER = 8
SECTION = 10

# Open the input file and read the file to memory (may be too big a
file? ~ 2MB?).
reader = csv.reader(file("sample.csv"))

def createFilename(teacher,title,number,section):
'''
We need to remove spaces from the fields for better formatting of
the file name
'''
import re
regex = re.compile('[^.A-Za-z0-9-_]')
filename = '%s_%s_%s_section%s.txt' % (teacher, title, number,
section)
return regex.sub('_', filename)

for row in reader:
filename = createFilename(row[TEACHER_NAME], row[COURSE_TITLE],
row[COURSE_NUMBER],

row[SECTION])
fileobj = file(filename, 'a')
newfile = csv.writer(fileobj)
newfile.writerow(row)
fileobj.close()
**************************************

Thanks to those who have helped!

Maik Röder <ro****@berg.net> wrote in message news:<ma**************************************@pyt hon.org>...
Hi TobyB,
Hi,
I've searched the group and need more information and guidance on this
issue I need to resolve next week. I work for the local school system
and I am working on a way to parse a CSV file of class lists from MS
Excel. It is a ~2MB file with all teachers and all their classes in
it. I thought I would use Python to do this since many people I know
tell me how great it is.


Pyhton is a good choice for treating texts.
The real sticking point is there are
duplicates of each teacher's classes embedded in the file (don't ask
why). I want to break up the source file into the seperate class
files without duplication and use the teachers name, coursecode and
section in the filename.

Example Data:
Last Name First Name Grade Period Teacher Name
SMITH JOHN 8 1 JONES SALLY

Student ID Course Code Course Title
12345678 1234 ALGEBRA I

Course Section Session
1 0
The course code and section number are the same in the duplicate
classes. The difference is that the session number changes. I'm
thinking that I will need to somehow iterate through the lines and
break the class when the course code changes and/or section change
(course codes can be the same but section numbers change with each
class). Then I have to monitor the session number to see if there is
a duplicate course code and section but a different session number
would indicate that the class is a duplicate. Essentially, the session
number will be 0, 1, or 2 for a total of three lists of the same
class. Hopefully that makes sense. Again don't ask why the data is
like this.

My humble attempts have not been very successful. I've been trying
the csv modules to read the file but I am not sure how to procede
after that.

Any guidance is greatly appreciated.


Use Python lists and dictionaries.

Best regards,

Maik Röder

Jul 18 '05 #5

P: n/a
TonyB wrote:
In any case, it appears
that the new files have some sort of additional line terminator that
creates a blank row in the outputted file making the importing of the
list impossible.
When writing to a file using csv.writer on Windows open the file in
binary format.
row[SECTION])
fileobj = file(filename, 'a')
newfile = csv.writer(fileobj)
newfile.writerow(row)
fileobj.close()

so
fileobj = file(filename, 'a')
becomes
fileobj = file(filename, 'ab')

That should fix it.

Waldek
Jul 18 '05 #6

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