Where am I going wrong with Sentinel or break in this Python code -

okay program done keeps running. need figure out sentinel or break needs go. have far in python. program suppose read pres on list , print them. there slice removing first 2 , last two.then prints list size 6 , proceeds give me 6 pres in alpha reverse order. have working other repeating end indefinitely. there has while loop display elements in list returned playlist.

pres = ['kennedy','johnson','nixon','ford','carter','reagan',\         'bush','clinton','bush','obama']  pres2 = pres[2:8]  def main():      names in pres:          print(names)       pr3=playlist(pres2)     while playlist !='6':             pr3 in pres2:                     print(pr3)   def playlist(pr):      size = len(pr)     print('list size now', size)      pr.sort()     pr.reverse()     return pr  main() 

now should when run it.

kennedy johnson nixon ford carter reagan bush clinton bush obama list size 6 reagan nixon ford clinton carter bush 

but instead after list size 6, last 6 presidents keeps repeating. , needs read vertically on own line.

it appears have problems understanding basics of programming. encourage read again courses had read.

nevertheless, here explanations:

• playlist function. while playlist !='6' loop verifying function object not string. different, so. if want compare result of function, have call it: playlist(pr), execute function , return list can store in variable.

• your playlist function returning list object. why try compare '6'? moreover, '6' not length of list. string. 6 length of list int.

• why use while loop since want 6 presidents being displayed once? not make sense. loop actions need repeated unknown number of times.

• as pres2 sliced pres @ beginning, length 6. length has never been higher, , assuming loop had been drafted, code inside never have been executed.

• when use for loop iterate trough list, variable written after for used alias represents current object iterated list. for pr3 in pres2: weird defined variable called pr3. if want display president inside list, use for name in pr3 did before.

let me show enhanced version of function, hoping manage understand better how works:

def main():      # print 10 presidents     name in pres:         print(name)      # print size of list contains 6 presidents     # then, sort list, reverse , return     # new list store pr3     pr3 = playlist(pres2)      # print 6 reverse sorted presidents     name in pr3:         print(name) 

did it? have absolutely no need use loop.