Michael Lewis wrote:
> I am trying to repeat a certain sequence in a range if a certain even
> occurs. Forgive me for not pasting my code; but I am not at the machine
> where it's saved.
>
> Basically, I want to get user input and append that input to a list only
> if the input is not already in the list. I want to do this x amount of
> times, but if the user input is already in the list, then I want to repeat
> that step in range(x).
>
> At the prompt, I want to ask the user for:
>
> Name 1:
> Name 2:
> Name 3:
> etc....
> but if the user input for Name 3 was the same as the user input for Name
> 2, then I want to ask the user again for Name 3 instead of continuing to
> Name 4.
>
> How can I do this?
Well, you are describing the algorithm pretty clearly: keep asking for a
name until the user enters a name that is not in the list of names already.
Here's a straightforward implementation:
>>> names = []
>>> for i in range(1, 4):
... while True:
... name = raw_input("Name %d: " % i)
... if name not in names:
... names.append(name)
... break
... print "Name %r already taken" % name
...
Name 1: Jack
Name 2: Jack
Name 'Jack' already taken
Name 2: Jack
Name 'Jack' already taken
Name 2: Jim
Name 3: Jack
Name 'Jack' already taken
Name 3: Jim
Name 'Jim' already taken
Name 3: Joe
>>> names
['Jack', 'Jim', 'Joe']
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