How to make a python list from a .csv list?

Question

I want to know how to make a .csv list into a python list which I can do plotting and calculating:

I used:

    fpath = r'C:112017\temp\tT.csv'
    with open(fpath,'r') as csvfile:
         reader = csv.reader(csvfile, delimiter=',')
         for row in reader:
             print(list(reader))

it gives me lists like this (which I dont' want):

    [['2014-12-30', '18.34244791666665'], ['2014-12-31', '18.540224913494818'], ['2015-01-01', '18.15729166666666'],......

If I use

    print(row)

it gives me lists like this (looks better but I still can not use it for calculating):

    ...        
    ['2016-07-27', '20.434809022479584']
    ['2016-07-28', '21.395138886239796']
    ['2016-07-29', '20.81571181284057']
    ['2016-07-30', '20.565711801250778']
    ...

How can I use panda to make a list? Or is there any easier way to achieve this? Is that possible to use something like:

    date = row[0]
    temp = row[1]
    lis = pd.DataFrame(date,temp)

I guess there are some basic mistakes, but I can't fix it by myself. Thank you for your time to help.

`list(reader)` in the loop is strange, as it stops immediately... what is the expected output? because the code you tried works as designed. — Jean-François Fabre, Nov 15 '17 at 10:07
The output from list(reader) was just like the first output, [['2014-12-30', '18.34244791666665'], ['2014-12-31', '18.540224913494818'], ...] — Jenny, Nov 15 '17 at 10:37

score 4 · Accepted Answer · answered Nov 15 '17 at 10:08

4

There is pandas.read_csv() method which will read the csv file and return a dataframe

Eg:

fpath = r'C:112017\temp\tT.csv'
df = pd.read_csv(fpath, delimiter=',', names=['date', 'temp'])

answered Nov 15 '17 at 10:08

Arun

1,933
2
28
46

Don't know why I got this error: OSError: Initializing from file failed – Jenny Nov 15 '17 at 10:32
@Jenny: Try this solution: https://stackoverflow.com/a/16952651/6619424 – Arun Nov 15 '17 at 10:45
The link is very useful! Thank you! – Jenny Nov 15 '17 at 11:41

Sagun Shrestha · Answer 2 · 2017-11-15T10:52:07.080

1

I guess you are trying to get the columns as list i.e. a list of dates and temperatures.

fpath = r'C:112017\temp\tT.csv'
with open(fpath,'r') as csvfile:
    reader = csv.reader(csvfile, delimiter=',')
    data = list(reader)

date, temp = list(map(list, zip(*data)))
# for python 2 use map(list,zip(*data))
# converting temp to float
temp = list(map(float,temp))

edited Nov 15 '17 at 10:52

answered Nov 15 '17 at 10:15

Sagun Shrestha

1,188
10
23

nice, but a conversion to float for `temp` list would be even better. – Jean-François Fabre Nov 15 '17 at 10:39
@Jean-FrançoisFabre Thanks for the suggestion, I have updated my answer. Also you can use list comprehension if you want. – Sagun Shrestha Nov 15 '17 at 10:53

score 0 · Answer 3 · answered Nov 15 '17 at 14:40

in my opinion if you want to perform calculations with data from a .csv file you should consider using pandas and numpy.

import pandas as pd
import numpy as np

# importing dataframe
df = pd.read_csv('filename.csv', delimiter=',')
# check the dataframe
print (df)

How to make a python list from a .csv list?

3 Answers3