Comments on: Python & Scratch Bubble sorts for KS3 http://www.suppertime.co.uk/blogmywiki/2015/10/python-bubble-sort-for-ks3/ reading, writing, coding, making Tue, 24 Oct 2023 13:43:21 +0000 hourly 1 http://wordpress.org/?v=3.1 By: marc http://www.suppertime.co.uk/blogmywiki/2015/10/python-bubble-sort-for-ks3/#comment-86081 marc Wed, 28 Oct 2015 09:50:39 +0000 http://www.suppertime.co.uk/blogmywiki/?p=2201#comment-86081 Yes you do need to do a test there but you don't need to keep count. So you can just set it to 1 as you say as a flag if there is a swap but as that is then acting as a boolean it suggests it isn't needed at all. Indeed, it isn't - just set "sorted" to true after the "while" statement & then set it to false if you do a swap. then delete the last "if" as no longer needed. ie change the while loop to: while not sorted: sorted = True #instead of swaps = 0 for i in range(len(numberList)-1): if numberList[i] > numberList[i+1]: temp = numberList[i] numberList[i] = numberList[i+1] numberList[i+1] = temp Sorted = False #if make a swap then sorted is false & so while loops again # no second if as if there has not been a swap then sorted has not changed from true but if there has then it is false So you save a variable and save an increment function. You still probably set Sorted to false several times but avoiding that takes more code & is less efficient. Bonus point to the kid who notices than you don't need to calculate (len(numberList)-1) every time in the "for" statement & so quicker to set a variable to that value before entering the while loop. Wow this is so much more fun than work.... marc Yes you do need to do a test there but you don’t need to keep count. So you can just set it to 1 as you say as a flag if there is a swap but as that is then acting as a boolean it suggests it isn’t needed at all. Indeed, it isn’t – just set “sorted” to true after the “while” statement & then set it to false if you do a swap. then delete the last “if” as no longer needed.

ie change the while loop to:
while not sorted:
sorted = True #instead of swaps = 0
for i in range(len(numberList)-1):
if numberList[i] > numberList[i+1]:
temp = numberList[i]
numberList[i] = numberList[i+1]
numberList[i+1] = temp
Sorted = False #if make a swap then sorted is false & so while loops again
# no second if as if there has not been a swap then sorted has not changed from true but if there has then it is false

So you save a variable and save an increment function. You still probably set Sorted to false several times but avoiding that takes more code & is less efficient.

Bonus point to the kid who notices than you don’t need to calculate (len(numberList)-1) every time in the “for” statement & so quicker to set a variable to that value before entering the while loop.

Wow this is so much more fun than work….

marc

]]> By: blogmywiki http://www.suppertime.co.uk/blogmywiki/2015/10/python-bubble-sort-for-ks3/#comment-86046 blogmywiki Tue, 27 Oct 2015 13:30:52 +0000 http://www.suppertime.co.uk/blogmywiki/?p=2201#comment-86046 Hi Marc. Thanks for commenting. You may well have a point! I think it's needed, or at least a 'swaps made in this run' flag is needed, as some pairs may not need swapping in a run through the list, and you don't want it to stop just because two numbers are in the right order (no swap). I need to have a think and a play! Hi Marc. Thanks for commenting. You may well have a point! I think it’s needed, or at least a ‘swaps made in this run’ flag is needed, as some pairs may not need swapping in a run through the list, and you don’t want it to stop just because two numbers are in the right order (no swap). I need to have a think and a play!

]]> By: marc http://www.suppertime.co.uk/blogmywiki/2015/10/python-bubble-sort-for-ks3/#comment-86032 marc Tue, 27 Oct 2015 10:12:07 +0000 http://www.suppertime.co.uk/blogmywiki/?p=2201#comment-86032 Why the swaps variable? It seems only to be used to determine whether to change sorted to true or not. Why not do that directly? i.e. after "if numberList[i] > numberList[i+1]:" , just put "sorted = True"? Keep up the good work! Why the swaps variable? It seems only to be used to determine whether to change sorted to true or not. Why not do that directly? i.e. after “if numberList[i] > numberList[i+1]:” , just put “sorted = True”?

Keep up the good work!

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