Convert CSV file to a dictionary of lists

Question

My csv file looks like this:

Name,Surname,Fathers_name
Prakash,Patel,sudeep
Rohini,Dalal,raghav
Geeta,vakil,umesh

I want to create a dictionary of lists which should be like this:

dict = {Name: [Pakash,Rohini,Geeta], Surname: [Patel,Dalal,vakil], Fathers_name: [sudeep,raghav,umesh]}

This is my code:

with open(ram_details, 'r') as csv_file:
csv_content = csv.reader(csv_file,delimiter=',')
header = next(csv_content)
if header != None:
    for row in csv_content:
        dict['Name'].append(row[0])

It is throwing an error that key does not exists? Also, if there is any better way to get the desired output?!! Can someone help me with this?

Answer 1

Your code looks fine. It should work, still if you are getting into any trouble you can always use defaultdict .

from collections import defaultdict 
# dict = {'Name':[],'Surname':[],'FatherName':[]}
d = defaultdict(list)
with open('123.csv', 'r') as csv_file:
    csv_content = csv.reader(csv_file,delimiter=',')
    header = next(csv_content)
    if header != None:
        for row in csv_content:
            # dict['Name'].append(row[0])
            # dict['Surname'].append(row[1])
            # dict['FatherName'].append(row[2])
            d['Name'].append(row[0])
            d['Surname'].append(row[1])
            d['FatherName'].append(row[2])

Answer 2

Please don't name a variable similar to a build in function or type (such as dict ).

The problem is that you haven't initialized a dictionary object yet. So you try to add a key and value to an object which is not known to be dict yet. In any case you need to do the following:

result = dict()  # <-- this is missing
result[key] = value

Since you want to create a dictionary and want to append to it directly you can also use python's defaultdict .

A working example would be:

import csv
from collections import defaultdict
from pprint import pprint

with open('details.csv', 'r') as csv_file:
    csv_content = csv.reader(csv_file, delimiter=',')
    headers = list(map(str.strip, next(csv_content)))
    result = defaultdict(list)

    if headers != None:
        for row in csv_content:
            for header, element in zip(headers, row):
                result[header].append(element)

pprint(result)

Which leads to the output:

defaultdict(<class 'list'>,
            {'Fathers_name': ['sudeep', 'raghav', 'umesh'],
             'Name': ['Prakash', 'Rohini ', 'Geeta  '],
             'Surname': ['Patel  ', 'Dalal  ', 'vakil  ']})

Note 1) my csv file had some extra trailing spaces, which can be removed using strip() , as I did for the headers .

Note 2) I am using the zip function to iterate over the elements and headers at the same time (this saves me to index the row).

Possible alternative is using pandas to_dict method ( docs )

Answer 3

You may try to use pandas to achieve that:

import pandas as pd


f = pd.read_csv('todict.csv')
d = f.to_dict(orient='list')

Or if you like a one liner:

f = pd.read_csv('todict.csv').to_dict('orient='list')

First you read your csv file to a pandas data frame (I saved your sample to a file named todict.csv). Then you use the dataframe to dict method to convert to dictionary, specifying that you want lists as your dictinoary values, as explained in the documentation.