Creating a dictionary from a csv file?

Question

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 rep

Answer 1

If you have:

1. Only 1 key and 1 value as key,value in your csv
2. Do not want to import other packages
3. Want to create a dict in one shot

Do this:

mydict = {y[0]: y[1] for y in [x.split(",") for x in open('file.csv').read().split('\n') if x]}

What does it do?

It uses list comprehension to split lines and the last "if x" is used to ignore blank line (usually at the end) which is then unpacked into a dict using dictionary comprehension.

Answer 2

You have to just convert csv.reader to dict:

~ >> cat > 1.csv
key1, value1
key2, value2
key2, value22
key3, value3

~ >> cat > d.py
import csv
with open('1.csv') as f:
    d = dict(filter(None, csv.reader(f)))

print(d)

~ >> python d.py
{'key3': ' value3', 'key2': ' value22', 'key1': ' value1'}

Answer 3

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

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)
        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)

Answer 4

You can also use numpy for this.

from numpy import loadtxt
key_value = loadtxt("filename.csv", delimiter=",")
mydict = { k:v for k,v in key_value }

Answer 5

Assuming you have a CSV of this structure:

"a","b"
1,2
3,4
5,6

And you want the output to be:

[{'a': '1', ' "b"': '2'}, {'a': '3', ' "b"': '4'}, {'a': '5', ' "b"': '6'}]

A zip function (not yet mentioned) is simple and quite helpful.

def read_csv(filename):
    with open(filename) as f:
        file_data=csv.reader(f)
        headers=next(file_data)
        return [dict(zip(headers,i)) for i in file_data]

Answer 6

Try to use a defaultdict and DictReader.

import csv
from collections import defaultdict
my_dict = defaultdict(list)

with open('filename.csv', 'r') as csv_file:
    csv_reader = csv.DictReader(csv_file)
    for line in csv_reader:
        for key, value in line.items():
            my_dict[key].append(value)

It returns:

{'key1':[value_1, value_2, value_3], 'key2': [value_a, value_b, value_c], 'Key3':[value_x, Value_y, Value_z]}