download log - modify and use last line - python-2.7

Question

I'm trying to shorten or simplify my code.
I want to download a log file from an internal server which is updated every 10 seconds, but I'm only running my script every 10 or 15 minutes.
The log file is semicolon seperated and has many rows in it I don't use. So my workflow is as following.
get current date in YYYYMMDD format
download the file
delay for waiting that the file is finished downloading
trim the file to the rows I need
only process last line of the file
delete the files
I'm new to python and if you could help me to shorten/simplify my code in less steps I would be thankful.
import urllib
import time
from datetime import date
today = str(date.today())
import csv
url = "http://localserver" + today + ".log"
urllib.urlretrieve (url, "output.log")
time.sleep(15)
with open("output.log","rb") as source:
rdr= csv.reader(source, delimiter=';')
with open("result.log","wb") as result:
wtr= csv.writer( result )
for r in rdr:
wtr.writerow( (r[0], r[1], r[2], r[3], r[4], r[5], r[15], r[38], r[39], r[42], r[54], r[90], r[91], r[92], r[111], r[116], r[121], r[122], r[123], r[124]) )
with open('result.log') as myfile:
print (list(myfile)[-1]) #how do I access certain rows here?

Answer 1

You could probably make use of the advanced module, requests as below. The timeout can be increased depending on the time it takes for the download to complete successfully. Furthermore, the two with open statements can be consolidated in a single line. What is more, in order to load the line one by one in to the memory, we can make use of iter_lines generator. Note that stream=True should be set in order to load line one at a time.
from datetime import date
import csv
import requests
# Declare variables
today = str(date.today())
url = "http://localserver" + today + ".log"
outfile = 'output.log'
# Instead of waiting for 15 seconds explicitly consider using requests module
# with timeout parameter
response = requests.get(url, timeout=15, stream=True)
if response.status_code != 200:
print('Failed to get data:', response.status_code)
with open(outfile, 'w') as dest:
writer = csv.writer(dest)
# Walk through the request response line by line w/o loadin gto memory
line = list(response.iter_lines())[-1]
# Decode the response to string and split line by line
reader = csv.reader(line.decode('utf-8').splitlines(), delimiter=';')
# Read line by line for the splitted content and write to file
for r in reader:
writer.writerow((r[0], r[1], r[2], r[3], r[4], r[5], r[15], r[38], r[39], r[42], r[54], r[90], r[91], r[92],
r[111], r[116], r[121], r[122], r[123], r[124]))
print('File written successfully: ' + outfile)