Python for non programmers, part 1

A good friend of mine (not an engineer) recently faced a problem. Customers sent in data samples (usually as comma-separated files) that needed to be processed and/or validated for conformance to a specification. My friend spent hours importing the files into spreadsheets and going through them manually. The data was large for a human (a few thousand rows), but small for a computer. My friend had some basic programming skills from college and early jobs, but over the years, those had become a bit rusty. I wondered if I could help, so here goes...

The objective:

• Getting my friend all the information needed with as little theory as possible
• Focus on the specific use case
• Keep it simple (no list comprehensions, or any of that stuff)
• Must work on windows machines with minimal system modifcations.

The final result will hopefully be a chain of simple exercises to get this person up to speed.

Lesson 1: Install python, read and write a csv file:

• Install python, version 2, from http://python.org/download/. Currently, the latest installer can be found here. Remember the folder of where python was installed.
• Optionally, install an editor like Notepad++ (otherwise, use regular notepad)
• Create a folder, for example c:\example
• Add a file called data.txt with the following three lines of content:

Row A,Row B,Row C
Hello,1,2
World,3,4

• Add a file called csvcopy.py with the following content (the leading whitespace in the last line is important):

import csv
infile = open('data.txt', 'rb')
in_csv = csv.reader(infile, delimiter=',')
outfile = open('data2.txt', 'wb')
out_csv = csv.writer(outfile, delimiter=',')
for row in in_csv:
  out_csv.writerow(row)

• Open a command prompt and switch to the folder that contains data.txt and csvcopy.py.
• Run "C:\Python\python.exe csvcopy.py" (path needs to be adjusted depending on where you installed python).
• Open the newly created file "data2.txt" and look at its content.
• Exercise: rename data.txt to data.csv and modify the program to write the result into data2.csv