[Tutor] What's going on?

Sun Apr 30 22:44:13 EDT 2023

I looked at your message again Ed and I see you ran the program several ways including just running the .py file on windows.

So my suggestion is to use whatever command line program you have, including those that let you redirect output to a file like the bash we bashed a few days ago. I tested the default shell on Windows of CMD like so:

C:\Users\xyz>echo "hi"
"hi"

C:\Users\xyz>echo "hi" >temp.txt

C:\Users\xyz>more temp.txt
"hi"

So it allows redirection and if you run python as in:

python file >temp.txt

Or something similar, and view it with a pager like I did that shows only a screen at a time, or you can use a text editor. Ideally, all the output will get captured as file I/O may not be as delicate as whatever comes to your screen. I have never had such a problem when I run python with output in RSTUDIO, idle, Jupyter Notebook and so on.

If that works, great.

And, of course, with a bit of work, you can change the internals of your code to slow down the output, redirect file descriptors for stdout, or just have it pause and ask what to do next. 

Your program seems to work and is logically sound. 

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------- Original Message -------
On Sunday, April 30th, 2023 at 10:32 PM, ThreeBlindQuarks <threesomequarks at proton.me> wrote:

> Ed,
> 
> Thank you for supplying code that works and is brief enough to try.
> 
> My only glitch was one of your comments lines that became two lines which resulted in an error easy to fix so it did not try to "trip".
> 
> I got lots of output but as I understand it, you simply wanted to do something N==10 times. You could have encapsulated all the calculations in a function which would cleanly have avoided some issues of your reusing variables.
> 
> So you initialize these each time:
> 
> res = []
> nums = []
> ct = []
> 
> Your next code segment seems to re-populate some of these variables
> 
> 
> I get this when I examine variables at the end:
> 
> ct: [0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
> nums: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
> 
> which makes me wonder if this method is one that could be done differently in perhaps a more Pythonic way. You do this:
> 
> for i in range(10):
> ct.append(0)
> nums.append(i)
> 
> No error here but consider you are asking for a group of N zeros in a row for the first and a sequence from 0 to N-1 for the second.
> 
> I personally might have combined all the beginning code into these three lines:
> 
> N = 10
> res = []
> nums = list(range(N))
> ct = [0] * N
> 
> Again, nothing wrong with your code so far. Just an alternate viewpoint and note I set a parameter called N to make the code flexible if changed at a single point.
> 
> This removes an explicit loop and replaces it with two hidden implicit loops, albeit perhaps implemented faster internally.
> 
> I am not clear on why you have commented out code about sleeping. It is hinting at something. Is there some concern you did not share? I am not aware any pause is needed unless you want results not to flow off the screen.
> 
> Again, just to show an alternative perspective, you can insert a line of code like this:
> 
> _ = input("Press RETURN to see next results:")
> 
> This stops processing after displaying a prompt and waits for the user to hit any keys and a return (and effectively ignores that) before continuing. Again, not really needed as you can often just scroll up in the output and see quite a bit.
> 
> Now I recall the earlier request was to pick random numbers and never use any one more than four times. I am not sure if your code plans on anything like variations of that. Your next section hard-codes in precisely thirty times in a loop that you shuffle the numbers (initially from 0 to 9) in place and then you pick just the first and append that to res for an eventual result.
> 
> random.shuffle(nums)
> res.append(nums[0])
> print(res)
> 
> That seems like a bit of extra work to shuffle the whole thing over and over just to get one at random. What is the advantage over just picking a random number from 0 to 9 each time rather than picking lots of them to re-arrange the deck chairs on the Titanic? But, FWIW, it does get you a random number to add to the growing collection.
> 
> The next section explains this odd choice as the list to choose from changes dynamically:
> 
> if ct[nums[0]] == 4:
> print( 'Removing', nums[0],nums )
> nums = nums[1:]
> print('leaving', nums )
> 
> This may have been your problem so I checked. The logic is that once you have used a number four times, remove it and shrink the pool of available to choose from to 9 then later 8 and so on. Is that carried out carefully? You are removing the zeroth item by making a copy of the rest of the list. I would consider an alternate of:
> 
> nums.pop(0)
> 
> Which throws away the first and changes the list in place. Note it can also be used to just remove the nth. So if you just picked a random number from zero to the current length of the list, I am guessing it might be easier to just remove any that reached 4 and never scramble an entire list.
> 
> The rest of the loop is just print statements.
> 
> So logically, what should happen in the inner loop? Thirty numbers should be chosen first from 10 possibilities so res should keep growing and stop at 30 entries. The ct variable always remains at length 10 with entries rising from 0 towards 4 and never exceeding it. The nums list should shrink and above 40 should disappear and perhaps cause problems beyond that as there is nothing to scramble and use. At 30, it should be safe. But ideally, your algorithm should break out of a loop if everything has hit 4, or alternately if the number of items to choose from reaches zero.
> 
> So I ran the code and I am embarrassed to say I did not see anything wrong. It seems to do exactly what it is designed to do. My guess is you are using something that cannot keep up with the I/O and produces glitches on your screen. The fact that it happens after the first run may be a clue that some buffer is being over-run or something.
> 
> So, yes, your sleep attempts make some sense but you may also consider redirecting the output to a file in one of many ways and then viewing the file with something like a text editor and seeing if that looks like you expect.
> 
> If so, there is nothing wrong with your program but something not quite great about some aspect of your environment.
> 
> Anyone else try to run this and get an odd output?
> 
> Q
> 
> 
> 
> 
> 
> 
> Sent with Proton Mail secure email.
> 
> 
> ------- Original Message -------
> On Sunday, April 30th, 2023 at 5:31 PM, Ed Connell edwinconnell at gmail.com wrote:
> 
> 
> 
> > Greetings,
> > 
> > I got interested in one of your earlier problems, but THAT PROBLEM is not
> > what I am asking about. It was to generate a random sequence, each taken
> > from a predefined pool. However, nothing is to be used more than four
> > times. Moderately interesting.
> > 
> > What I am asking about is this. The first time it runs perfectly. However
> > subsequent runs, sooner or later, foul up.
> > ###############################
> > import random
> > import time
> > 
> > for run in range(10): #usually 1 but trying multiple runs through in one
> > trip.
> > 
> > # build result, number choices, and choice count lists
> > res = []
> > nums = []
> > ct = []
> > 
> > for i in range(10):
> > ct.append(0)
> > nums.append(i)
> > 
> > print('\n\n', run, ' start\n')
> > 
> > #time.sleep(0.016) # seems to work for 0.016 or more uncommented
> > 
> > for _ in range( 30 ): # tried 10 - 40
> > random.shuffle(nums)
> > res.append(nums[0])
> > print(res)
> > ct[nums[0]] += 1
> > if ct[nums[0]] == 4:
> > print( 'Removing', nums[0],nums )
> > nums = nums[1:]
> > print('leaving', nums )
> > 
> > print()
> > print('numbers left',sorted(nums))
> > print('result',res)
> > print('number used of each',ct)
> > ####################################
> > The problem seems to be a difference between printing and calculation speed
> > but maybe not.
> > 
> > I tried mostly using Geany, but also just ran the .py file.
> > 
> > The bad output has incomplete lines as well as missing sections.
> > 
> > I will appreciate your ideas.
> > 
> > Oh, I am running on Windows 11, an hp with AMD 7.
> > 
> > Ed Connll
> > --
> > I have a right and a left brain, but there is nothing right in the left one
> > and there is nothing left in the right one!
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