Simple Example of Externalizing Data

Externalize the name of the file containing student data.

Requires: python-decouple (pip3 install python-decouple)

First: run gitstudents.py. It works, but the filename is hardcoded. Not very maintainable.

Let's improve it:

1. create a file named .env containing this:

   # name of file containing student data
   CSVFILE = "students.csv"
   

2. In gitstudents.py, add:

   from decouple import config

3. And read the filename from the configuration file (.env):

   datafile = config('CSVFILE')
   data = open(datafile)

4. Run the code. It should still work.

   • You can rename the file (and change .env) and it still works -- no need to modify code.

5. Externalize the number of students to print (10). In .env add:

   count = 10
   

   In the Python code:

   count = config('count', default=10, cast=int)  

   cast=int means to convert the value to int; the default is to return the value as a string.

6. Run it. It should still work. But now you want to print 20 students.

7. In .env change the value of count to 20. Run the code again. Does it work?

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Python-decouple Doc: https://pypi.org/project/python-decouple/

How to Use Decouple: https://simpleisbetterthancomplex.com/2015/11/26/package-of-the-week-python-decouple.html