title: Python Using List/Multiple Arguments in Pool Map
body: <p>I am trying to pass a list as a parameter to the <code>pool.map(co_refresh, input_list)</code>. However, <code>pool.map</code> didn't trigger the function <code>co_refresh</code>. And also no error returned. It looks like the process hung in there.</p>
  
  <p><strong>Original Code:</strong></p>
  
  <pre><code>from multiprocessing import Pool
  import pandas as pd
  import os
  
  account='xxx'
  password='xxx'
  threads=5
  co_links='file.csv'
  
  input_list=[]
  
  pool = Pool(processes=threads)
  def co_refresh(url, account, password, outputfile):
  
      print(url + ' : ' + account + ' : ' + password + ' : ' + outputfile)
  
      return;
  
  link_pool = pd.read_csv(co_links, skipinitialspace = True)
  
  for i, row in link_pool.iterrows():
  
      ln = (row.URL, account, password, os.path.join('e:/', row.File_Name.split('.')[0] + '.csv'))
  
      input_list.append(ln)
  
  pool.map(co_refresh, input_list)
  
  pool.close()
  </code></pre>
  
  <p>However, it never triggered the function <code>co_refresh</code>. How can I use the list as a parameter to be passed to my function?</p>
  
  <p><strong>Old Question (Simplified):</strong></p>
  
  <p>I have below input_list, which is a <code>list</code> of <code>list</code>:</p>
  
  <pre><code>[a1, b1, c1, d1]
  [a2, b2, c2, d2]
  [a3, b3, c3, d3]
  </code></pre>
  
  <p>I have the function as below:</p>
  
  <pre><code>def func(a, b, c, d)
     ###
      return;
  </code></pre>
  
  <p>I would like to use multiprocess for this function <code>func</code>:</p>
  
  <pre><code>from multiprocessing import Pool
  pool = Pool(processes=5)
  pool.map(func, input_list)
  pool.close()
  </code></pre>
  
  <p>However, it never triggered the function <code>func</code>. How can I use the list as a parameter to be passed to my function?</p>