title: Iterate through a list, and convert string “numbers” to integers
body: <p>I am trying to convert the numbers in the list from strings to integers, while leaving other strings unchanged. </p>
  
  <p>I have prepared the following code, however I am receiving an error saying, “argument of type ‘int’ is not iterable”.</p>
  
  <p>Why is this not working, or what would be a better way of going about this?</p>
  
  <pre><code>test_list = ['the','dog','ran','down','984','47','the','chicken','4','77']
  numSet = '0123456789'
  
  
  for i in range(0, len(test_list)):
      for j in numSet:
          if j in test_list[i]:
              test_list[i]=int(test_list[i])
  
  print(test_list)
  </code></pre>