Using '' with open, reader '' functions

Question

I got a problem with this code:

import csv
with open('gios-pjp-data.csv', 'r') as data:
    l = []
    reader = csv.reader(data, delimiter=';') 
    next(reader) 
    next(reader)  # I need to skip 2 lines here and dont know how to do it in other way
    l.append(# here is my problem that I will describe below)

So this file contains about 350 lines with 4 columns and each one is built like this:

Date ; float number ; float number ; float number

Something like this:

2017-01-01;56.7;167.2;236.9

Now, I dont know how to build a function that would append first float number and third float number to the list on condition that its value is >200. Do you have any suggestions?

Can you provide your expected output?

Sociopath
– Sociopath

2018-01-20 11:27:23 +00:00
Commented Jan 20, 2018 at 11:27 — Sociopath
– Sociopath, Commented Jan 20, 2018 at 11:27
output : l= [236.9]

Piotrek Wcisło
– Piotrek Wcisło

2018-01-20 14:57:53 +00:00
Commented Jan 20, 2018 at 14:57 — Piotrek Wcisło
– Piotrek Wcisło, Commented Jan 20, 2018 at 14:57

C14L · Accepted Answer · 2018-01-20 11:28:02Z

2

List comprehentions if you don't have too many items in the file.

l = [x[1], x[3] for x in reader if x[1] > 200]

Or a similar function that would yield each line, if you have a huge number of entries.

def getitems():
    for x in reader:
        if x[1] > 200:
            yield x[1], x[3]

l = getitems()  # this is now an iterator, more memory efficient.
l = list(l)  # now its a list

answered Jan 20, 2018 at 11:28

C14L

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1 Comment

Jean-François Fabre Over a year ago

you can do a gencomp as well no need for yield: l = (x[1], x[3] for x in reader if x[1] > 200)

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