Execute multiple inner functions

Question

I'm currently working on an ETL process where I have all the separate functions working, however, I'm still having troubles to get it work in a main function.

def etl(url):

    def extract(url):
        return url_json_file
    extract()

    def transform(url_json_file):
        return json_transformed
    transform()

    def load(json_transformed):
        load_json_to_db
    load()
    
pass

This is the ETL schema. My objective is, that I pass the outter function etl() a URL string, and from that point the process goes like this:

• extract(): Takes in that URL string, scrape it and performs a json.loads() and returns it.
• transform(): Takes in the loaded json file, transforms it and returns a clean new dictionary with the data on that previous JSON.
• load(): Takes in the clean JSON dict. and loads it to X database

PROBLEM: I'm probably doing a wrong return action, even if I set those return values to global, the process DOES NOT END. It usually returns this error: [WinError 6] The handle is invalid

My question, therefore, is, how can I make an inner function take the returned value or operation from a previous function. I would appreciate any hint or tip.

Answer 1

def etl(url):
    def extract(url):
        url_json_file = url   ## Do smt.
        print("first step")
        return url_json_file

    def transform(url_json_file):
        json_transformed = url_json_file ## Do smt.
        print("second step")
        return json_transformed

    def load(json_transformed):
        ###do some db insert operations
        print("third step")
        db_send = json_transformed
        return db_send
    return "ETL: " + load(transform(extract(url)))

print(etl(url="https://www.google.com"))

The result should be :

first step
second step
third step
ETL: https://www.google.com