drbunsen drbunsen - 4 months ago 32
Python Question

Creating a dictionary from a csv file?

I am trying to create a dictionary from a csv file. The first column of the csv file contains unique keys and the second column contains values. Each row of the csv file represents a unique key, value pair within the dictionary. I tried to use the

and
csv.DictWriter
classes, but I could only figure out how to generate a new dictionary for each row. I want one dictionary. Here is the code I am trying to use:

import csv

with open('coors.csv', mode='r') as infile:
reader = csv.reader(infile)
with open('coors_new.csv', mode='w') as outfile:
writer = csv.writer(outfile)
for rows in reader:
k = rows[0]
v = rows[1]
mydict = {k:v for k, v in rows}
print(mydict)


When I run the above code I get a
ValueError: too many values to unpack (expected 2)
. How do I create one dictionary from a csv file? Thanks.

Answer

I believe the syntax you were looking for is as follows:

with open('coors.csv', mode='r') as infile:
    reader = csv.reader(infile)
    with open('coors_new.csv', mode='w') as outfile:
        writer = csv.writer(outfile)
        mydict = {rows[0]:rows[1] for rows in reader}

Alternately, for python <= 2.7.1, you want:

mydict = dict((rows[0],rows[1]) for rows in reader)
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