[kwlug-disc] Any Python Experts?

John Driezen jdriezen at sympatico.ca
Thu Sep 13 10:15:25 EDT 2018


I am trying to write a program to plot scrap copper prices using python, 
sqlite3 and plotly.  I have run into a bit of a snag.  The plotly 
library only works with Python 2.7, and I wrote a scraper to work with 
Python 3.5.  When I read the data from the sql database using Python 
2.7.2 I get an unexpected 'u' in front of my date values.  Using the 
Python 3.5.2 interpreter produces the correct results.

john at LinuxMint18 ~/scrap_prices_scraper $ cat read_data.py
import sqlite3
import os

DB_FILE = '/home/john/scrap_prices_scraper/scrapmetalprices.db'

# check for existing database file
if os.path.isfile(DB_FILE):
     connection = sqlite3.connect(DB_FILE)

     cursor = connection.execute ("SELECT * from PRICES WHERE 
MATERIAL='#1 Bright Copper'")

     price=[]
     dates=[]
     for row in cursor:
         dates.append(row[4])    # store date in list
         price.append(row[2])     # store price in list
         print (dates, price)

     connection.close
else:
     print("Database does not exist.")

raise SystemExit
john at LinuxMint18 ~/scrap_prices_scraper $ python --version
Python 2.7.12
john at LinuxMint18 ~/scrap_prices_scraper $ python3 --version
Python 3.5.2

The incorrect results with the Python 2.7 interpreter:

john at LinuxMint18 ~/scrap_prices_scraper $ python read_data.py
([u'2018-08-31'], [3.13])
([u'2018-08-31', u'2018-09-04'], [3.13, 3.03])
([u'2018-08-31', u'2018-09-04', u'2018-09-10'], [3.13, 3.03, 3.03])
([u'2018-08-31', u'2018-09-04', u'2018-09-10', u'2018-09-12'], [3.13, 
3.03, 3.03, 3.03])

The correct results with the Python3 interpreter:

john at LinuxMint18 ~/scrap_prices_scraper $ python3 read_data.py
['2018-08-31'] [3.13]
['2018-08-31', '2018-09-04'] [3.13, 3.03]
['2018-08-31', '2018-09-04', '2018-09-10'] [3.13, 3.03, 3.03]
['2018-08-31', '2018-09-04', '2018-09-10', '2018-09-12'] [3.13, 3.03, 
3.03, 3.03]
john at LinuxMint18 ~/scrap_prices_scraper $ exit
exit

Script done on Thu 13 Sep 2018 09:57:20 AM EDT

Does anyone have any suggestions?

John Driezen




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