On 8/11/2010 2:04 PM Laurens Vets said...
Hello list,
I'm learning Python and I'm currently facing an issue with a small
script I'm writing.
I need to generate a list of 30 numbers randomly chosen from 1, 2, 3, 4,
5 & 6. However, I cannot have more than 2 numbers which are the same
next to each other. I came up with the following (Please ignore the fact
that I'm trying to avoid an IndexError in a stupid way :)):
import random
reeks = []
while len(reeks) <= 1:
number = random.randrange(1, 7, 1)
reeks.append(number)
while len(reeks) <= 29:
nummer = random.randrange(1, 7, 1)
if nummer != reeks[-1] and nummer != reeks[-2]:
reeks.append(nummer)
print reeks
So far so good (I think). From what I can see from the output, I get 30
numbers, without more than 2 being the same next to each other.
However, I wanted to look deeper in the above script and I created the
following:
import random
iteraties = 5
cijferreeks = 6
aantal_cijfers = iteraties * cijferreeks
reeks = []
while len(reeks) <= 1:
nummer = random.randrange(1, cijferreeks + 1, 1)
print 'Nummer: ', nummer
print 'Reeks: ', reeks
reeks.append(nummer)
print '\n'
while len(reeks) <= aantal_cijfers:
nummer = random.randrange(1, cijferreeks + 1, 1)
print 'Nummer: ', nummer
print 'Voorlaatste vd reeks (-2): ', reeks[-2]
print 'Laatste vd reeks (-1): ', reeks[-1]
print 'Reeks: ', reeks
if nummer != reeks[-1] and nummer != reeks[-2]:
You're testing here if nummer is niet gelijk van _both_ vorige twee
nummers, maar je wil testen als het niet gelijk is van _either_ nummer:
if nummer != reeks[-1] _or_ nummer != reeks[-2]:
For then it is true that
nummer == reeks[-1] and nummer == reeks[-2]
You should review/create or/and truth tables to determine the validity
of your logical tests. Also, particularly when starting, it is known
that negatives often lead to confusion, with use of multiple negatives
leading to even more confusion. Next time, try eliminating the
negatives and look for a positive test when you have this kind of issue.
Then you might have written:
if nummer == reeks[-1] and nummer == reeks[-2]:
print "it's the same as the prior two"
else:
reeks.append(nummer)
HTH,
Emile
reeks.append(nummer)
else:
print 'Nummer: ', nummer, 'is gelijk aan vorige 2 nummers: ', reeks[-1],
'&', reeks[-2], '!'
print '\n'
print reeks
When I run that, I can see there's something wrong with my if statement,
it triggers the else condition even when the 2 previous numbers in my
list are not the same... I'm not sure what is happening here...
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