python Traceback (most recent call last): & TypeError: can only concatenate tuple (not "str") to tuple

Question

im having trouble Modifying the script so that the data structure shared between the producer and the consumer is a list of 2-tuples instead of a list of strings and i cant seem to figure out whats going wrong.

   #!/usr/bin/env python 
   # demonstrate coroutines in Python 
    """
   +  implements a typical producer/consumer algorithm 
   +  the consumer is a subroutine and main() is the producer
   +  producer sends a job request to consumer; waits for consumer to receive it
   +  the consumer waits for job request, does job, waits again
   +  keywords: 
   +  yield waits on producer - passes argument to producer at handoff
   +  next() sends job to consumer w/o msg
   +  send() sends job to consumer with msg 
   """
   import sys 
   def printjob(name):
   name += " "
   sys.stdout.write(name)
   """
+  CONSUMER 
+  'yield stuff' passes stuff back to the producer; when control resumes a 
+  message (it may be empty) is available from the producer as the return 
+  value from yield; note: cannot remove everything from the list since
+  the dereference to jobs[i] in yield is invalid
"""
def consumer(jobs):
  i = -1
# as long as something is in the jobs list keep processing requests
  while jobs:
      i = (i + 1) % len(jobs)
      # yield passes control back to producer with the ith job name
      getRequest = yield jobs[i]    # waits for request from producer 
      if getRequest:    # if getRequest is not empty process it
          request,name,num = getRequest
          if request == "add":
              jobs.append(name)
              jobs.append(num)
              sys.stdout.write("\nADD ")
          elif request == "remove" and name in jobs:
              jobs.remove(name)
              buf = "\nREMOVE " + name + "\n"
              sys.stdout.write(buf) 
   print "\nNo jobs left to do!\n" 
def producer(jobs):
   con = consumer(jobs)                   # start the consumer 
   buf = "Initial job list (" + str(len(jobs)) + "): "
   sys.stdout.write(buf)
   for i in range(len(jobs)):
      printjob(con.next())            # next sends job to consumer w/ no msg  
   printjob(con.send(("add", "iron",44)))  # send sends job to consumer w/ msg
   sys.stdout.write("\n")
   for i in range(len(jobs)):
      printjob(con.next())
   con.send(("remove","fold",33))
   for i in range(len(jobs)):
      printjob(con.next()) 
   con.send(("remove","wash",11))
   for i in range(len(jobs)):
      printjob(con.next()) 
   print "\nProducer Done."
"""
+ MAIN 
+ acts as the producer coroutine
+ next passes a job to the consumer with no message passing
+ send passes a job to the consumer with a message 
"""
if __name__ == "__main__":             # this means initialize once only
   jobs = [("wash",11),("dry",22),("fold",33)]        # tuble list
   pro = producer(jobs)

Any help would be greatly appreciated!

Answer 1

The error is, I suspect, pointing to this line:

name += " "

...because you're (exactly as the error says) attempting to concatenate a string " " to a tuple ("wash",11) . What exactly are you trying to do with that line? If you're trying to just print some string form of the tuple, use the str function:

sys.stdout.write(str(name) + '\n')