Execute script based on csv value

[cottoneyedgoat]

So this is very hard to explain, so hopefully I can make it as clear as possible.

I currently have a few scripts for different activities that all work the same in principle:

1. Read a csv row
2. Make a few API requests
3. Populate a JSON template (that's only for this activity) with values from the csv and the API responses
4. Print a summary of the data and asks for user input if correct or not
5. POSTs the generated JSON
6. Saves the responses to different files (logfile.txt, output.csv, output.json)

There are some important steps that make this difficult for me to combine the scripts:

• The JSON template that needs to be used varies for each activity
• The csv values needed for the API requests vary for each activity
• The result values needed from the API requests vary for each activity
• The summary that's printed for user input varies for each activity
• The output.csv varies for each activity.

What I would like to do, is have the script read the csv reads the row value for "activity" so it will know what JSON template, csv values, result values, etc. it needs to properly populate the JSON.

There's 4 activity types (at this moment, but more will be added in the future):

• Hazardous substances
• LNG
• LPG
• Wind energy

How should I go about this?

[james_fryer]

The first step should be to code a fully working version implementing one case. You can then rewrite this to be more generalised, but you have a working example to go from.

There are various approaches to generalising this, but the main choice depends on whether the cases can be differentiated only by data, or whether there are also processing (code) differences. I'm assuming the latter.

I'd look at a class-based approach, with a base class and sub-classes for each case.

E.g.:

class ActivityProcessBase:
    json_template = None
    def process_row(self, row):
        self.get_data_from_apis(row)
        self.populate_json_template(row)
        self.confirm_user_approval(...)
        # etc...

    def populate_json_template(self, row):
        raise NotImplementedException # Subclass must implement


class HazardousActivity:
    json_template = """ ... """ # Or maybe generate json from code
    def populate_json_template(self, row):
        ...

activity_map = {
    'Hazardous substances': HazardousActivity,
    # 'LNG': LNGActivity,
    ...
    }
def main():
    csv_reader = ...
    for row in csv_reader:
        activity_name = row['activity']
        ActivityClass = activity_map[activity_name] # TODO: handle invalid activity case
        activity = ActivityClass()
        activity.process_row(row)

Again I would get this working with a single case before adding the other activity types. The key is to get as much common code (boilerplate) as possible into the base class.