[Tutor] Re: Recursive list checking

[Jeffrey Maitland]

Jeffrey Maitland writes: 

> joe_schmoe writes:  
> 
>> Dear Pythonites  
>> 
>> I am looking for a more elegant solution to a piece of code that is too 
>> unwieldy and reptitive. The purpose of the code is for a new addition to 
>> a list to check whether it is a duplicate of a list element already a 
>> member of that list, and if so to regenerate itself randomly and to 
>> perform the same check again until such time as it is unique.
>> For example, this is what I am currently doing:  
>> 
>> =============code block ========================  
>> 
>>    # generate unique numbers and append to list
>>    nmbr01 = random.randrange( 1, 20 )
>>    nmbr_list.append( nmbr01 )  
>> 
>>    nmbr02 = random.randrange( 1, 20 )
>>    # check for duplicates and re-generate a number if needed
>>    while nmbr02 in nmbr_list:
>>        nmbr02 = random.randrange( 1, 20 )
>>    nmbr_list.append( nmbr02 )  
>> 
>>    nmbr03 = random.randrange( 1, 20 )
>>    while nmbr03 in nmbr_list:
>>        nmbr03 = random.randrange( 1, 20 )
>>    nmbr.append( nmbr03 )  
>> 
>> ================================================  
>> 
>> This method works, but increasing the numbers to be appended makes the 
>> code excessively long. I can't see anything in list methods that seems to 
>> do the trick, so anybody want to make a suggestion please?  
>> 
>> TIA
>> /j
>> _______________________________________________
>> Tutor maillist  -  Tutor at python.org
>> http://mail.python.org/mailman/listinfo/tutor
> 
> Well I would start by doing something like.  
> 
> nmbr_list = []
> value = int(raw_input("Input the number of items you wish to generate"))  
> 
> for i in range(value):
>  if i == 0:
>    nmbr = random.randrange( 1, 20 )
>    nmbr_list.append( nmbr01 )
>  else:
>     nmbr = random.randrange( 1, 20 )
>     # check for duplicates and re-generate a number if needed
>     while nmbr in nmbr_list:
>        nmbr = random.randrange( 1, 20 )
>     nmbr_list.append( nmbr )  
> 
> I hope that helps. or gives you an idea.
> Jeff  
> 
> _______________________________________________
> Tutor maillist  -  Tutor at python.org
> http://mail.python.org/mailman/listinfo/tutor

Err just noted that I screwed up on my idea.. here.. is a better party same 
idea edited some. 

nmbr_list = []
value = int(raw_input("Input the number of items you wish to generate")) 

# so this loops the value specified times, as this will add that number to 
list too.  so a range of 1 - 20 in random order if 20 is the sepcified 
number.
for i in range(value):
if i == 0:
  nmbr = random.randrange( 1, value )
  nmbr_list.append( nmbr )
else:
   nmbr = random.randrange( 1, value )
   # check for duplicates and re-generate a number if needed
   while nmbr in nmbr_list:
      nmbr = random.randrange( 1, value )
   nmbr_list.append( nmbr ) 


Jeff 

also feel free to ask me more speicifc questions via email if you think they 
won't help the cominity at all.