I have had an issue where I can't get the While loop to terminate.

    userinput = ("")

while userinput != ("Search" or "Add"):
  userinput = input("Search or Add?")

  if userinput == "Search":
    Search()
  elif userinput == "Add":
    print("run add request")
  else: print("please choose from the following two options.")
  
  

Edit: I am sorry the changes have worked. I think after I implemented the changes I had an issue with the Shell running the previous version. Sometimes I have no idea what is happening. Thank you all again.

Edit Edit: Placed the original code back in as I did not take into account that it would confuse anyone looking for their own solution. I am quite new in terms of usage of the site. Thanks again for the help

CodePudding user response：

The issue is with your while test. A couple of things:

1. You can't use or like this. or needs two full conditions that resolve to true or false. Here you have one condition userinput != "Search" and a string "Add". So it's always going to return True since a non-zero value is always True.

   As an example:

   if "Add": print("true")
   
   >>true
   

   Instead:

   userinput != "Search" or userinput != "Add"
   

2. or is not correct when testing two negations like !=. One of the two conditions will always return true. For instance if you input "Add" then the condition userinput != "Search" will be True and your while loop will continue since True or False = True. So on and so forth. Instead you want an and.

    while userinput != "Search" and userinput != "Add":
   

As I suggested in my comment though, it's probably just easier to use the not in operator on a list:

while userinput not in ['Search','Add']:

This way as your list grows your test stays nice and small/condense.

Also, while this is just my opinion, I applaud your original pre-edit code where you supplied the condition for breaking your while loop in the while statement instead of doing while True:. Having had many years of bug hunting and feature adding and hotfixing, I know every time I see while True: I'm going to be hunting through hundreds of lines of codes looking for every break. while True: and break has its time and place (I imagine), but I feel like it should be an exception use-case, not the rule.

CodePudding user response：

My solution looks like this:

userinput = ""

while userinput != "Exit":
    userinput = input("Search, Add or Exit: ")

    if userinput == "Search":
        print("run search request")
    elif userinput == "Add":
        print("run add request")
    elif userinput != "Exit": 
        print("please choose from Search, Add or Exit.")

Notes:

• Variable userinput is initialised to "". It doesn't need to be a tuple, ("")
• I introduced an 'Exit' option. We loop until we encounter Exit. No need for break or continue
• I changed the prompt to a colon and a space, and also show the three options.
• We compare the input to the three options. If nothing valid, print an error message

CodePudding user response：

As an alternative, you can use the following, using continue in the else clause, and break at the end of the while block. This way, it is easier to add more elif clauses, without potentially forgetting a break statement.
(It also doesn't require setting a default value for userinput, since that is done as the first thing in the while loop.)

while True:
    userinput = input("Search or Add?")

    if userinput == "Search":
        Search()
    elif userinput == "Add":
        print("run add request")
    else: 
        print("please choose from the following two options.")
        continue
    break

CodePudding user response：

Using the word break will break you out of a while loop, like this:

while True:
    break

Place break where you want the while loop to end.

The problem is that once the input is received, and when the input meets the end condition of the while loop, and it isn't able to reach the code checking for the condition! Try this:

while True:
  userinput = input("Search or Add?")

  if userinput == "Search":
    Search()
    break
  elif userinput == "Add":
    print("run add request")
    break
  else: print("please choose from the following two options.")

CodePudding user response：

The format was not correct in the while condition statement part, You can try out this...

userinput = ("")

while userinput not in ["Search", "Add"]:
  userinput = input("Search or Add?")

  if userinput == "Search":
    Search()
  elif userinput == "Add":
    print("run add request")
  else: print("please choose from the following two options.")