🌐 Mailman 3 April 2023 - Tutor - python.org

What's going on?
by Ed Connell May 1, 2023

May 1, 2023

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!

3 5

Handle and display results
by sam muhammed April 28, 2023

April 28, 2023

Dears, Good day! I am a beginner in Python programming and the field of classification images using CNN I try to study the publicly available code in Google Collab or Kaggle to reuse it. I have a problem with how to display the resulting images after training the model (as one image with its label at a time) beginning from the first image until the last one in the dataset. So that in the end, I get all the images that have been trained in the model, not just one image or 9 images as in code). I would like your help correcting the code in order to get all the results of the predictions images. I will attach the program code for you to fix it. All the best, SAM.

3 2

bash heredoc and python
by David Lowry-Duda April 27, 2023

April 27, 2023

I like to use python as a simple commandline calculator. I only just learned that it's possible to do something like the following in bash ``` $ python <<EOF import math print('multiple lines') print(math.pi) ``` and python will happily run this. I had thought this wouldn't work, and that python would instead complain that there was no file with some amalgamated name. I discovered this by an accident, but googling shows of course that this isn't new or anything. I would have expected this to run with "python - <<EOF" instead of "python <<EOF", as the `-` indicates to read from stdin. So I opened up the python manpage to see about this, and saw nothing there (not even about what `-` is supposed to mean!). Then I went to https://docs.python.org/3/using/cmdline.html#command-line to see if I could learn more, and I don't see much there either. There is a somewhat cryptic remark: "In non-interactive mode, the entire input is parsed before it is executed." I guess python does something like: check to see if args were given, if not then check for standard input and then run it noninteractively? Do you think this is an intended behavior, or is this merely an undocumented implementation detail? - DLD

5 5

Hello
by Bernard Kofi Agboado April 24, 2023

April 24, 2023

Good morning, please how best can I understand the loops.?

6 8

Python project organisation
by Phil April 23, 2023

April 23, 2023

I'm looking suggestions for organising my python projects. I had, until recently, all of my python projects stored in the one directory (~/Python), all 298 of them. This has become almost unmanageable so I split my projects into multiple sub-directories named Tkinter, Wxpython, etc. and named each project, for example those under the Tkinter sub-directory, as "tkinter_project_name.py". This is, or was, better but still not good. This problem has now come to a head because because my upgraded Linux distribution now requires the use of virtual environments, otherwise "pip3 install" fails. So I created a virtual environment "~/.venv/bleak/bin" named after the name of the module that I needed to upgrade. It probably should be named after the project instead. The code for the project is now in that virtual environment directory which brings me to my question. Should I create a virtual environment for each project, I don't think so? If I do, won't that make the PYTHONPATH unwieldy with hundreds of directories needing to be added to PYTHONPATH? I can see a case where a project should have it's own environment and that's where a project includes images that are solely used by that project. At the moment images and custom classes are all stored under python's global environment. -- Regards, Phil

4 7

Strange results when using not operation.
by Magnus Myrefors April 21, 2023

April 21, 2023

Hello ! I am currently Reading a ”Beginning Python” book, and when I did some tests with the not operation in the IDLE python Shell I saw som strange results. When I typed ’ not”A” == False ’ the result was ’True’ and when I typed ’ not”A” == True ’ the result was ’True’ again. I got similar results when I typed ’ not(2) == False ’ and ’ not(2) == True ’ which both gave the result ’True’ . When I put the whole left side in paranthesis like this: ’ (not”A”) == False’ and ’ (not”A”) == True ’ the results were different. Magnus Skickades från E-post för Windows

3 2

Re: [Tutor] Strange results when using not operation.
by Alan Gauld April 21, 2023

April 21, 2023

On 21/04/2023 15:26, Magnus Myrefors via Tutor wrote: > Hello ! > > I am currently Reading a ”Beginning Python” book, and when > I did some tests with the not operation in the IDLE python > Shell I saw som strange results. When I typed ’ not”A” == False ’ > the result was ’True’ and when I typed ’ not”A” == True ’ the result was ’True’ again. It would help if you actually copy/pasted the actual code and output. Above I see single quotes around the code, I assume you did not type those at the Python prompt? > I got similar results when I typed ’ not(2) == False ’ > and ’ not(2) == True ’ which both gave the result ’True’ . > When I put the whole left side in paranthesis like this: ’ (not”A”) == False’ and ’ (not”A”) == True ’ > the results were different. The answer to this seemingly weird behaviour lies in how Python performs the equality comparison. The relevant part of the language reference says: """The default behavior for equality comparison (== and !=) is based on the identity of the objects. Hence, equality comparison of instances with the same identity results in equality, and equality comparison of instances with different identities results in inequality. A motivation for this default behavior is the desire that all objects should be reflexive (i.e. x is y implies x == y).""" Here is an interactive session including your examples plus a few more along with my commentary: Python 3.10.4 (v3.10.4:9d38120e33, Mar 23 2022, 17:29:05) [Clang 13.0.0 (clang-1300.0.29.30)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>> not "A" == False True >>> not "A" == True True Python reads these as: not("A" == False) and not("A" == True") So lets look at the parens: >>> ("A" == False) False >>> ("A" == True) False So both sets of parens are false because the string "A" is not equal to either of the boolean values. The operator uses an ID comparison. And the string has a different identity to the booleans. >>> not "A" False >>> (not "A") == False True >>> (not "A") == True False By putting the parens around the left side you evaluate not "A" first resulting in a boolean value(False in this case) and then compare that boolean value to the literal booleans. Thus you get a differrent result since False == false is indeed True and False == True is indeed False. >>> not(2) == False True >>> not(2) == True True The same applies here. Python sees this as: not ((2) == False) and not ((2) == True) and 2 has a different ID to both True and False so both parens return False and their negations return True, which is what you saw. Now the language reference goes on to describe cases where the behaviour has been changed from the default for some types so ID comparisons are not always used. Here is the link so you can study it all in detail. https://docs.python.org/3/reference/expressions.html#value-comparisons It may take you a few read throughs! -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos

1 0

Re: [Tutor] Help
by Thurman Hill April 21, 2023

April 21, 2023

I need help with this question. Fill in the blanks to complete the “all_numbers” function. This function should return a space-separated string of all numbers, from the starting “minimum” variable up to and including the “maximum” variable that's passed into the function. Complete the for loop so that a function call like “all_numbers(3,6)” will return the numbers “3 4 5 6”. def all_numbers(minimum, maximum): return_string = "" # Initializes variable as a string # Complete the for loop with a range that includes all # numbers up to and including the "maximum" value. for ___ # Complete the body of the loop by appending the number # followed by a space to the "return_string" variable. ___ # This .strip command will remove the final " " space # at the end of the "return_string". return return_string.strip() print(all_numbers(2,6)) # Should be 2 3 4 5 6 print(all_numbers(3,10)) # Should be 3 4 5 6 7 8 9 10 print(all_numbers(-1,1)) # Should be -1 0 1 print(all_numbers(0,5)) # Should be 0 1 2 3 4 5 print(all_numbers(0,0)) # Should be 0 On Wed, Apr 12, 2023 at 12:51 PM Thurman Hill <thurmonium(a)gmail.com> wrote: > I’m getting a type error when I put this into the blanks… Please help. > I've been stuck for weeks… > > > > > > > > > > Fill in the blanks to print the even numbers from 2 to 12. > > > > number = range(2,12+1,2) # Initialize the variable > > while number > 0: # Complete the while loop condition > > print(number, end=" ") > > number # Increment the variable > > > > # Should print 2 4 6 8 10 12 > > > > Error: > > Error on line 2: > > while number > 0: # Complete the while loop condition > > TypeError: '>' not supported between instances of 'range' and 'int' >

2 1

Oops concepts class vs methods.
by mhysnm1964＠gmail.com April 20, 2023

April 20, 2023

All, In the past I sent some code through related to WX python that I am working on to see if I can make an accessible home book-shelf library program. Thus the reasons for these OOPS questions. I am trying to work out if I should create the following code as a generic method or class. My simplistic understanding of Oops. * A class is an object such as creating a GUI window. * Method is the action you want to do Such as creating an edit control or performing a database query. * Properties are the variables of the class / method. I have a range of WX methods that creates a control on the panel or window. For example: class RecordPanel(wx.Panel): def __init__(self, parent, app): wx.Panel.__init__(self, parent=parent) # defining the book object. self.book = None # Create the controls for the panel # adding controls to a sizer. #sizer = wx.BoxSizer(wx.VERTICAL) sizer = wx.FlexGridSizer(rows=0, cols=2, vgap=10, hgap=10) self.title_label = wx.StaticText(self, label="Title:") self.title_text = wx.TextCtrl(self, size=(300, -1)) sizer.Add(self.title_label, flag=wx.ALIGN_LEFT) sizer.Add(self.title_text, flag=wx.EXPAND) sizer.Add(wx.StaticText(self, label="About Authors:"), flag=wx.ALIGN_LEFT) self.about_author_text = wx.TextCtrl(self, size=(300, 100), style=wx.TE_MULTILINE) sizer.Add(self.about_author_text, flag=wx.EXPAND) # Set the publisher field self.publisher_label = wx.StaticText(self, label="Publisher:") self.publisher_text = wx.TextCtrl(self, size=(300, -1)) sizer.Add(self.publisher_label, flag=wx.ALIGN_LEFT) sizer.Add(self.publisher_text, flag=wx.EXPAND) # Set the series field self.series_label = wx.StaticText(self, label="Series:") self.series_text = wx.TextCtrl(self, size=(300, -1)) sizer.Add(self.series_label, flag=wx.ALIGN_LEFT) sizer.Add(self.series_text, flag=wx.EXPAND) . more declaring of controls and events to be added to the page. self.SetSizer(sizer) # applies the controls to the page. AS you can tell, the creation of the edit fields and the list boxes use the same syntax with different variables. Is it possible to create a class with a couple of methods to reduce the lines above to simplify the debugging and readability of the code? Below is my attempt and could be completely wrong: Class WindowControls(sizer, Label, label_flags, control_flags, xPosition, yPosition): # sizer is the wx sizer object # label - the label to be used for the control # label_flags - the flags used to style and align the control. # control_flags - flag parameters for the control. # xPosition and yPosition - the size of the control. Def EditControl(self) self.control_label = wx.StaticText(self, label=f"{label}:") self.control_text = wx.TextCtrl(self, size=(xPosition, yPosition)) sizer.Add(self.control_label, flag=flags) sizer.Add(self.title_text, flag=control_flags) return sizer WindowsControls. EditControl(self.sizer, "title", wx.ALIGN_LEFT, wx.EXPAND, 300, -1) I hope the above makes sense. As I really an unsure if I am on the right path here or using Oops in the right way. As I do get confused when to use the "self" instance. Sean

2 2

OOPs and general Python questions.
by mhysnm1964＠gmail.com April 20, 2023

April 20, 2023

All, I have some really broad and general questions to ask. What is a super class? Does python care the order of classes and methods? If you are using "python -m pdb script_name", can you reload the file using this debugging tool? I couldn't find anything which mention this? Chat.gpt references the ability of modifying code while the program is being executed. How difficult is this to achieve? A high level answer is all I need. Sean

4 7