Python – Nested Loops

I am having a problem with a loop in python to get the desired result. Here is my issue.

First, I have 1 text file: urls.txt. This file has multiple URLs. Second, I have multiple json files. Lets say there are 5 json files.

I want to process first n lines of the urls.txt file with 1.json file and then next n lines of urls.txt file with 2.json file and so on. After all the 5 json files are used, I want to start from 1.json file again and repeat the process until all the lines in urls.txt files are processed.

In my case I wanted to rotate the json files after each 100 lines of urls.txt

I have written some code to do that but unfortunately, I am not able to figure out how to repeat the operation once all the json files are used.

batch_size = 100

JSON_KEY_FILE_PATH = "json_files/"
JSON_FILENAME = '*.json'
json_file_list = glob.glob(JSON_KEY_FILE_PATH + JSON_FILENAME, recursive=True)
itr_length = len(json_file_list)

from itertools import count
def UrlCall(URL_FILE):   
    with open(URL_FILE, mode='r') as urllist:   
        for j in range(0,itr_length): 
            for i in count():  
                line = urllist.readlines(20)                         
                print ('===>' + str(i) + '===>' + str(line))
                if (i/batch_size).is_integer() and line != '' and i != 0 and j != itr_length:
                    # #define the json message
                    print ("Value of J" + str(j))    
                    print ("JSON FILE IN USE:" + str(json_file_list[j]))        
                    if j == itr_length-1:
                        print ("====>RESTARTING JSON EXECUTION")
                        time.sleep(10)
                        print ("Value of J" + str(j))   
                        print ('===>' + str(i) + '===>' + str(line)) 
                        print ("JSON FILE IN USE:" + str(json_file_list[j]))
                        return  
                    break

This code is existing after after all the json files are used. But I want to restart using the json files range again and process the next n line in urls.txt file.

Answer

You can use itertools.cycle(json_file_list) to loop through the list repeatedly.

You can use one of the techniques in What is the most “pythonic” way to iterate over a list in chunks? to iterate over the file in groups of N lines.

Then you can zip them to process them together.

from itertools import cycle, zip_longest

def grouper(iterable, n, fillvalue=None):
    args = [iter(iterable)] * n
    return zip_longest(*args, fillvalue=fillvalue)

def url_call(url_file, json_file_list):
    with open(url_file) as f:
        for json_file, lines in zip(cycle(json_file_list), grouper(f, batch_size)):
            json_data = json.load(open(json_file))
            for line in lines:
                if line:
                    # do something with line and json_data