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
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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.
The special case for i==0 is not needed, in this case the test for nmbr in nmbr_list will fail and nmbr will be added to the list.
But if you are trying to get n random elements from range(m) you are probably better off using random.sample(), I think it does exactly what you want:
>>> random.sample(xrange(10000000), 10)
[274075, 2925710, 7715591, 8236811, 1161108, 5804222, 2385884, 9236087, 5603149, 8473299]
If you actually want *all* elements of the range in random order, use random.shuffle(): >>> l=range(20) >>> random.shuffle(l) >>> l [13, 7, 6, 9, 3, 10, 1, 8, 4, 0, 18, 12, 11, 17, 19, 5, 16, 15, 2, 14]
You might also want to look at random.choice()...
Kent
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