Read in the first column of a CSV in Python

Question

I have a CSV (mylist.csv) with 2 columns that look similar to this:

jfj840398jgg     item-2f
hd883hb2kjsd     item-9k
jie9hgtrbu43     item-12
fjoi439jgnso     item-3i

I need to read the first column into a variable so I just get:

jfj840398jgg
hd883hb2kjsd
jie9hgtrbu43
fjoi439jgnso

I tried the following, but it is only giving me the first letter of each column:

import csv
list2 = []
with open("mylist.csv") as f:
    for row in f:
        list2.append(row[0])

So the results of the above code are giving me list2 as:

['j', 'h', 'j', 'f']

Answer 1

You should split the row and then append the first item

list2 = []
with open("mylist.csv") as f:
    for row in f:
        list2.append(row.split()[0])

You could also use a list comprehension which are pretty standard for creating lists:

with open("mylist.csv") as f:
    list2 = [row.split()[0] for row in f]

Answer 2

You can also use pandas here:

import pandas as pd
df = pd.read_csv(mylist.csv)

Then, getting the first column is as easy as:

matrix2 = df[df.columns[0]].as_matrix()
list2 = matrix2.tolist()

This will return only the first column in list. You might want to consider leaving the data in numpy, if you're conducting further data operation on the result you get.