[NEWB] Dictionary instantiation?

[Shane Geiger]

#!/usr/bin/python
"""
EXAMPLE USAGE OF PYTHON'S CSV.DICTREADER FOR PEOPLE NEW TO PYTHON

Python - Batteries Included(tm)

This file will demonstrate that when you use the python CSV module, you
don't have to remove the newline characters, as between "acorp_ Ac" and
"orp Foundation" and other parts of the data below.

It also demonstrates python's csv.DictReader, which allows you to read a
CSV record into a dictionary.

This will also demonstrate the use of lists ([]s) and dicts ({}s).

If this doesn't whet your appetite for getting ahold of a powertool
instead of sed for managing CSV data, I don't know what will.

"""

####  FIRST: CREATE A TEMPORARY CSV FILE FOR DEMONSTRATION PURPOSES
mycsvdata = """
"Category","0","acorp_ Ac
orp Foundation","","","Acorp Co","(480) 905-1906","877-462-5267 toll
free","800-367-2228","800-367-2228","info at acorp.or
g","7895 East Drive","Scottsdale","AZ","85260-6916","","","","","","Pres
Fred & Linda ","0","0","1","3","4","1"

"Category","0","acorp_ Bob and Margaret Schwartz","","","","317-321-6030
her","317-352-0844","","","","321 North Butler Ave.","In
dianapolis","IN","46219","","","","","","Refrigeration
man","0","1","2","3","4","0"

"Category","0","acorp_ Elschlager,
Bob","","","","","702-248-4556","","","TropBob at aol.com","7950 W.
Flamingo Rd. #2032","Las Vega
s","NV","89117","","","","","","guy I met","0","1","2","3","4","1"

"""

##  NOTE:  IF YOU HAVE A RECORD SEPARATOR WITHIN QUOTES, IT WILL NOT BE
TREATED LIKE A RECORD SEPARATOR!
##   Beef|"P|otatos"|Dinner Roll|Ice Cream


import os, sys
def writefile(filename, filedata, perms=750):
        f = open(filename, "w")
        f.write(filedata)
        os.system("chmod "+str(perms)+" "+filename)
        f.close()

file2write = 'mycsvdata.txt'
writefile(file2write,mycsvdata)

# Check that the file exists
if not os.path.exists(file2write):
    print "ERROR: unable to write file:", file2write," Exiting now!"
    sys.exit()

#   ...so everything down to this point merely creates the
# temporary CSV file for the code to test (below).



####  SECOND:  READ IN THE CSV FILE TO CREATE A LIST OF PYTHON
DICTIONARIES, WHERE EACH
#  DICTIONARY CONTAINS THE DATA FROM ONE ROW.  THE KEYS OF THE
DICTIONARY WILL BE THE FIELD NAMES
#  AND THE VALUES OF THE DICTIONARY WILL BE THE VALUES CONTAINED WITHIN
THE CSV FILE'S ROW.

import csv

### NOTE: Modify this list to match the fields of the CSV file.
header_flds =
['cat','num','name','blank1','blank2','company','phone1','phone2', \
          
'phone3','phone4','email','addr1','city','state','zip','blank3', \
          
'blank4','blank5','blank6','blank7','title','misc1','misc2','misc3', \
           'mics4','misc5','misc6']

file2open = 'mycsvdata.txt'

reader = csv.DictReader(open(file2open), [], delimiter=",")
data = []
while True:
    try:
        # Read next "header" line (if there isn't one then exit the loop)
        reader.fieldnames = header_flds
        rdr = reader.next()
        data.append(rdr)
    except StopIteration: break


def splitjoin(x):
    """ This removes any nasty \n that might exist in a field
    (of course, if you want that in the field, don't use this)
    """
    return ''.join((x).split('\n'))


####  THIRD: ITERATE OVER THE LIST OF DICTS (IN WHICH EACH DICT IS A
ROW/RECORD FROM THE CSV FILE)

# example of accessing all the dictionaries once they are in the list
'data':
import string
for rec in data:   # for each CVS record
    itmz = rec.items()  # get the items from the dictionary
    print "- = " * 20
    for key,val in itmz:
        print key.upper()+":  \t\t",splitjoin(val)
                # Note: splitjoin() allows a record to contain fields
with newline characters




Matt_D wrote:
> Hello there, this is my first post to the list. Only been working with
> Python for a few days. Basically a complete newbie to programming.
>
> I'm working with csv module as an exercise to parse out a spreadsheet
> I use for work.(I am an editor for a military journalism unit) Not
> trying to do anything useful, just trying to manipulate the data.
> Anyway, here's the code I've got so far:
>
> import csv
> import string
> import os
>
> #Open the appropriate .csv file
> csv_file = csv.reader(open("D:\\Python25\\BNSR.csv"))
>
> #Create blank dictionary to hold {[author]:[no. of stories]} data
> story_per_author = {}
>
> def author_to_dict(): #Function to add each author to the dictionary
> once to get initial entry for that author
>     for row in csv_file:
>         author_count = row[-1]
>         story_per_author[author_count] = 1
>
> #Fetch author names
> def rem_blank_authors(): #Function to remove entries with '' in the
> AUTHOR field of the .csv
>     csv_list = list(csv_file) #Convert the open file to list format
> for e-z mode editing
>     for row in csv_list:
>         author_name = row[-1]
>         if author_name == '': #Find entries where no author is listed
>             csv_list.remove(row) #Remove those entries from the list
>
> def assign_author_to_title(): #Assign an author to every title
>     author_of_title = {}
>     for row in csv_file:
>         title = row[3]
>         author = row[-1]
>         author_of_title[title] = author
>
>
> assign_author_to_title()
> print author_of_title
>
> --
>
> Ok, the last two lines are kind of my "test the last function" test.
> Now when I run these two lines I get the error:
>
> Traceback (most recent call last):
>   File "D:\Python25\Lib\SITE-P~1\PYTHON~1\pywin\framework
> \scriptutils.py", line 310, in RunScript
>     exec codeObject in __main__.__dict__
>   File "D:\Python25\csv_read.py", line 33, in <module>
>     print author_of_title
> NameError: name 'author_of_title' is not defined
>
> I am guessing that the author_of_title dict does not exist outside of
> the function in which it is created? The concept of instantiation is
> sort of foreign to me so I'm having some trouble predicting when it
> happens.
>
> If I call the assign_author_to_title function later, am I going to be
> able to work with the author_of_title dictionary? Or is it best if I
> create author_of_title outside of my function definitions?
>
> Clearly I'm just stepping through my thought process right now,
> creating functions as I see a need for them. I'm sure the code is
> sloppy and terrible but please be gentle!
>   


-- 
Shane Geiger
IT Director
National Council on Economic Education
sgeiger at ncee.net  |  402-438-8958  |  http://www.ncee.net

Leading the Campaign for Economic and Financial Literacy


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