First time attempting to thread using concurrent.futures-Why do I get no output?

Question

I'm very new to python, so there could be multiple things wrong with my code. But I can't debug because I literally get no output, including no error. Would love some help. I'm in python 3.5. Cheers!

print('starting')
def simple_function(comic_start, comic_end):  
    for urlNumber in range(comic_start, comic_end):
        print('Downloading page http://xkcd.com/%s...' % (urlNumber))       
        driver = selenium.webdriver.PhantomJS()
        driver.get('http://xkcd.com/%s' % (urlNumber))
        print('finding page')
        form= driver.title
        print(driver.title)   
    driver.quit()
with concurrent.futures.ThreadPoolExecutor(max_workers=10) as executor:
    executor.map(simple_function, (1, 100))

Output:

runfile('/Users/Seansmac/Desktop/Python/my_classroom/threading_training/concurrent.f1.py', wdir='/Users/Seansmac/Desktop/Python')
starting

EDIT: This is a similar Q to this, Concurrent.futures usage guide - a simple example of using both threading and processing, but like the OP said, the answer there is too complicated!

Answer 1

You were mapping a tuple with two values to the function. On each mapping it was sending a single argument, but your function takes two arguements comic_start and comic_end

To see this, you could take out your other arguement and do:

def simple_function(first_arg):
    print(first_arg)

with cf.ThreadPoolExecutor(max_workers=10) as executor:
     executor.map(simple_function, (1, 100))

Result:

1
100

Modified Code:

import concurrent.futures as cf

def simple_function(_range):

    #fill with driver stuff etc
    for num in _range:
        print('Downloading page http://xkcd.com/%s...' % (num))       

_max = 200 #max range you want
workers = 10
with cf.ThreadPoolExecutor(max_workers=workers) as e:

    cs= _max // workers #chunksize to split across threads

    #we chunk the range to be split across the threads so you can iterate
    #over the chunked range in the mapped function.

    #x + cs if x + cs <= _max else _max next upper bound by chunksize but 
    #we don't want to exceed the maximum range you want, so we default to _max
    #if the next upper bound exceeds this

    #x - 1 if x!= 0 else x, start initial range at 0, and last upper
    #bound is exclusive so x - 1 if were not at the initial range.
    ranges = [range(x - 1 if x != 0 else x, x + cs if x + cs <= _max else _max) 
              for x in range(0, _max, cs)]

    e.map(simple_function, ranges)