title: TypeError: must be str, not datetime.timedelta
body: <p>here is my code it works fine for the first print and the give me this error 
  TypeError: must be str, not datetime.timedelta</p>
  
  <pre><code>import datetime
  hour = datetime.datetime.now().hour
  tomorrow = datetime.datetime.now()
  for i in range(50):
      hour += 1
      print(hour)
      if hour &gt;= 23:
          tomorrow = tomorrow + datetime.timedelta(days=1)
          tomorrow = tomorrow.strftime('%d/%m/%Y')
          hour = 9
          print (tomorrow)
  </code></pre>
  
  <p>here is the output : </p>
  
  <pre><code>13
  14
  15
  16
  17
  18
  19
  20
  21
  22
  23
  07/12/2017
  10
  11
  12
  13
  14
  15
  16
  17
  18
  19
  20
  21
  22
  23
  Traceback (most recent call last):
    File "C:\Users\hamza.salhi\Desktop\datetime test.py", line 8, in &lt;module&gt;
      tomorrow = tomorrow + datetime.timedelta(days=1)
  TypeError: must be str, not datetime.timedelta
  </code></pre>
  
  <p>please can someone tell me why it works fine at first then i get that error </p>