CSV to dictionary

Question

I need some help with an assiment:

Write a function that opens the file Exports2012.csv and returns a map for the 10-top products among the Estonian exports. The map should associate the name of the product with its corresponding value in USD.

For convenience, you should covert the string '$2,268,911,208.49' into a float value.

Example of CSV:

#,HS,Name,Value (USD),Percent
1,8517,Telephones,"$2,823,450,843.60",15.38%
2,2710,Refined Petroleum,"$2,124,413,818.52",11.57%
3,8703,Cars,"$371,092,090.84",2.02%
4,7204,Scrap Iron,"$331,463,406.48",1.81%
5,8544,Insulated Wire,"$319,352,873.32",1.74%
6,4011,Rubber Tires,"$242,977,533.70",1.32%
7,8708,Vehicle Parts,"$241,059,109.78",1.31%
8,8429,Large Construction Vehicles,"$239,589,588.65",1.31%
9,4407,Sawn Wood,"$238,358,904.17",1.30%
10,4418,Wood Carpentry,"$237,521,163.59",1.29%
11,7210,Coated Flat-Rolled Iron,"$213,137,606.81",1.16%
12,9404,Mattresses,"$208,042,615.08",1.13%
13,4403,Rough Wood,"$206,112,209.11",1.12%
14,9403,Other Furniture,"$202,900,185.49",1.11%
15,8504,Electrical Transformers,"$202,856,149.28",1.10%

I know how to extract 2. and 3. columns, but I'm stuck at this point.

import csv
f= open('EstonianExports2011.csv', 'rb')
archive = csv.reader(f, delimiter=',')
arch_dict = {}
arch_dict = {row[2]: row[3]for row in archive}
print arch_dict

I'd appreciate any help.

Not related, but the assignment says "write a function". You should eventually write this as a function, not a plain script ;o) — heltonbiker, Oct 27 '14 at 23:08
Have a look here: http://stackoverflow.com/questions/20304824/sort-dict-by-highest-value — thefragileomen, Oct 27 '14 at 23:19

Padraic Cunningham · Accepted Answer · 2014-10-27T23:43:38.020

Your file is already sorted from highest to lowest so you need only take the first ten lines after the header, you also need to strip the $ sign and replace the ,'s:

import csv
with open('EstonianExports2011.csv', 'rb')as f:
    archive = list(csv.reader(f, delimiter=','))[1:11] # get lines 1 to 10
    arch_dict = {row[2]: float(row[3].strip("$").replace(",","")) for row in archive}

arch_dict
{'Rubber Tires': 242977533.7, 'Cars': 371092090.84, 'Vehicle Parts': 241059109.78, 'Insulated Wire': 319352873.32, 'Scrap Iron': 331463406.48, 'Telephones': 2823450843.6, 'Sawn Wood': 238358904.17, 'Large Construction Vehicles': 239589588.65, 'Wood Carpentry': 237521163.59, 'Refined Petroleum': 2124413818.52}

In [2]: s = "$213,137,606.81"

In [3]: s.strip("$") # strips from the ends of a string
Out[3]: '213,137,606.81'

In [5]: s.strip("$").replace(",","") # combine with replace to remove the commas
Out[5]: '213137606.81'

Making it a function should be pretty straight forward.

score 0 · Answer 2 · answered Oct 27 '14 at 23:22

Since this is an assignment, I won't (at least initially) provide explicit code, but rather a suggestion for an algorithm:

Let product = row[2] and valuestring = row[3] in your file;
Take only the part of valuestring between first and last characters;
Remove commas from the trimmed valuestring;
Convert to float;
Save this to a list of pairs (product and value), probably using zip function;
Make your dictionary using the function sorted(zipped_list, key=lambda l:l[1] in a dictionary comprehension like your current one.

CSV to dictionary

2 Answers2