Recently, I was required to process bunch of huge CSV and perform the output. I wrote a simple python program but it was dreadfully slow.
I thought why not make it process through multiple threads. Python is notorious for not having a good support for concurrency. Some of it is because of its Global Interpreter lock
Recent versions of python > 3.x , do have multiprocessing and multithreading modules built in.
Honestly, I find the whole world of multiprocessing / multithreading very confusing in python world.
Below is a sample program, which reads the CSV line by line and submits it to a pool of 50 workers, running concurrently.
from multiprocessing import Pool from random import randint from time import sleep import csv import requests import json def orders_v4(order_number): response = requests.request("GET", url, headers=headers, params=querystring, verify=False) return response.json() newcsvFile=open('gom_acr_status.csv', 'w') writer = csv.writer(newcsvFile) def process_line(row): ol_key = row['ORDER_LINE_KEY'] order_number=row['ORDER_NUMBER'] orders_json = orders_v4(order_number) oms_order_key = orders_json['oms_order_key'] order_lines = orders_json["order_lines"] for order_line in order_lines: if ol_key==order_line['order_line_key']: print(order_number) print(ol_key) ftype = order_line['fulfillment_spec']['fulfillment_type'] status_desc = order_line['statuses']['status_description'] print(ftype) print(status_desc) listrow = [ol_key, order_number, ftype, status_desc] writer.writerow(listrow) newcsvFile.flush() def get_next_line(): with open("gom_acr.csv", 'r') as csvfile: reader = csv.DictReader(csvfile) for row in reader: yield row f = get_next_line() t = Pool(processes=50) for i in f: results = t.map_async(process_line, (i,)) results.get()