🌐 Mailman 3 August 2022 - Python-list - python.org

Re: Persistent Error: Python was not found
by Dennis Lee Bieber Aug. 15, 2022

Aug. 15, 2022

On Mon, 15 Aug 2022 14:38:25 +1000, Mike Dewhirst <miked(a)dewhirst.com.au> declaimed the following: >If you want to execute a python script without first opening a cmd >prompt, you need a bat file or shortcut which contains the command line >you want executed. Give that a double-click and it should also work. > I've never had to do that... But I have file associations set up so that .py is considered to be an executable file. Just double-clicking on the file will run it. The problem is that it will open a command shell, run, and then close the command shell UNLESS one explicitly codes some sort of "hold" at the end of the program jnk = input("Press return to exit") .pyw extension does not open the command shell -- but is meant for programs that use one of the various GUI frameworks, which is probably more than the new-comer is ready to attack. -- Wulfraed Dennis Lee Bieber AF6VN wlfraed(a)ix.netcom.com http://wlfraed.microdiversity.freeddns.org/

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Persistent Error: Python was not found
by Jonathan Owah Aug. 15, 2022

Aug. 15, 2022

Good day, Great job on making Python easily accessible. I'm using a Windows 10, 64gb HP EliteBook. I've been trying to configure my laptop to run python scripts. This is the error I keep getting: Python was not found; run without arguments to install from the Microsoft Store, or disable this shortcut from Settings > Manage App Execution Aliases. Everything I've tried has failed. I've uninstalled and reinstalled I've added to path, both user and system path,manually and from fresh installation I've downloaded from Microsoft Store I've gone to manage app aliases and switched off I've used Git Bash, Powershell, cmd I'm able to check my python version: 3.10.6. I can't do anything else and it's really frustrating. I've been at it for days, I don't know what else to do. Thanks in advance for your help. Regards

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Parallel(?) programming with python
by Andreas Croci Aug. 15, 2022

Aug. 15, 2022

tI would like to write a program, that reads from the network a fixed amount of bytes and appends them to a list. This should happen once a second. Another part of the program should take the list, as it has been filled so far, every 6 hours or so, and do some computations on the data (a FFT). Every so often (say once a week) the list should be saved to a file, shorthened in the front by so many items, and filled further with the data coming fom the network. After the first saving of the whole list, only the new part (the data that have come since the last saving) should be appended to the file. A timestamp is in the data, so it's easy to say what is new and what was already there. I'm not sure how to do this properly: can I write a part of a program that keeps doing its job (appending data to the list once every second) while another part computes something on the data of the same list, ignoring the new data being written? Basically the question boils down to wether it is possible to have parts of a program (could be functions) that keep doing their job while other parts do something else on the same data, and what is the best way to do this.

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Conecting to MySQL
by Guilherme Campos Aug. 15, 2022

Aug. 15, 2022

Hello folks, trying to connect to MYSQL it appears the error msg below: InterfaceError: 2003: Can't connect to MySQL server on 'localhost:3306' (111 Connection refused) [image: conexao.png] How can i fix that.? thanks in advance Guilherme Campos Belo Horizonte - MG

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RE: [Tutor] (no subject)
by avi.e.gross＠gmail.com Aug. 15, 2022

Aug. 15, 2022

How long? Not fibbing but infinite is infinite and I simply so not have the time. This is so such an EASY question that you need to show some work to interest us. You can do this in ANY programming language so explain if there is a reason you ask here or ... The real question is what you want. Do you want an algorithm, perhaps in a function, that returns the first N numbers in the sequence, or one that can start with an alternate sequences than the usual 0/1 or perhaps do you want a generator that will return one number at a time infinitely, or until the world ends, or someone pulls a power cord, whichever is sooner? -----Original Message----- From: Tutor <tutor-bounces+avi.e.gross=gmail.com(a)python.org> On Behalf Of Phindile Julia Sent: Sunday, August 14, 2022 12:49 PM To: tutor(a)python.org Subject: [Tutor] (no subject) Hey how to create a Fibonacci list? _______________________________________________ Tutor maillist - Tutor(a)python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor

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Re: Parallel(?) programming with python
by Dennis Lee Bieber Aug. 11, 2022

Aug. 11, 2022

On Wed, 10 Aug 2022 19:33:04 +0200, "Dieter Maurer" <dieter(a)handshake.de> declaimed the following: >Schachner, Joseph (US) wrote at 2022-8-9 17:04 +0000: >>Why would this application *require* parallel programming? This could be done in one, single thread program. Call time to get time and save it as start_time. Keep a count of the number of 6 hour intervals, initialize it to 0. > >You could also use the `sched` module from Python's library. <sigh> Time to really read the library reference manual again... Though if I read this correctly, a long running action /will/ delay others -- which could mean the (FFT) process could block collecting new 1-second readings while it is active. It also is "one-shot" on the scheduled actions, meaning those actions still have to reschedule themselves for the next time period. -- Wulfraed Dennis Lee Bieber AF6VN wlfraed(a)ix.netcom.com http://wlfraed.microdiversity.freeddns.org/

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cols_justification
by Helmut Weingrill Aug. 10, 2022

Aug. 10, 2022

I installed Python 3.11 0b3. In the IDLE, cols_justification works fine in my program "sg.Table". When installing Pycharm 2022.2 later, "cols_just.." does not work. Error message: File "H:\pf\PyFibu\FIBU.py", line 85, in beg_buchen [sg.table(values=list field, headings=header, ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ TypeError: Table.__init__() received an unexpected keyword argument 'cols_justification'. Please, I need help - thanks!

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Re: Parallel(?) programming with python
by Andreas Croci Aug. 9, 2022

Aug. 9, 2022

Thank you for your reply. On 08.08.22 14:55, Julio Di Egidio wrote: > Concurrent programming is quite difficult, plus you better think > in terms of queues than shared data... Do you mean queues in the sense of deque (the data structure)? I ask because I can see the advantage there when I try to pop data from the front of it, but I don't see the sense of the following statement ("than shared data"). I mean, I called my structure a list, but it may well be a queue instead. That wouldn't prevent it from being shared in the idea I described: one function would still append data to it while the other is reading what is there up to a certain point and calculate the FFT of it. But, an easier and often > better option for concurrent data access is use a (relational) > database, then the appropriate transaction isolation levels > when reading and/or writing. > That would obviusly save some coding (but would introduce the need to code the interaction with the database), but I'm not sure it would speed up the thing. Would the RDBMS allow to read a table while something else is writing to it? I doubt it and I'm not sure it doesn't flush the cache before letting you read, which would include a normally slow disk access. Andreas > Julio

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RE: Parallel(?) programming with python
by avi.e.gross＠gmail.com Aug. 8, 2022

Aug. 8, 2022

Stefan, You are correct that the goal of a lock is to do something rather quickly and atomically, so your design should not do something complex or long before releasing the lock. In your example, you have a producer adding data as regularly as every second and another that wakes up rarely and processes all the data since the last time. So you may want to augment the code you had to do something fast like point another variable at the data gathered so far and move the original variable to an empty list or whatever. Then you release the lock within fractions of a second and let the regular job keep adding to the initially empty list while the other part of the code processes without a lock. A design like the above has the busy worker constantly checking the lock. An alternative if you are sure the other process will only show up almost exactly at 6 hours on the clock, is to have the busy one check the time instead, but that may be more expensive. Still other architectures are possible, such as writing to not a single list for six hours, but some data structure with multiple sub-lists such as one where you switch every minute or so. The second process can note how many entries there are at the moment, and does all but the last and notes the location so the next time it starts there. This would work if you did not need every last bit of data as the two do not interfere with each other. And no real locks would be needed as the only thing the two parts share is the position or identity of the current last fragment which only one process actually touches. Just some ideas. Lots of other variations are very possible. -----Original Message----- From: Python-list <python-list-bounces+avi.e.gross=gmail.com(a)python.org> On Behalf Of Stefan Ram Sent: Monday, August 8, 2022 7:21 AM To: python-list(a)python.org Subject: Re: Parallel(?) programming with python Andreas Croci <andrea.croci(a)gmx.de> writes: >Basically the question boils down to wether it is possible to have >parts of a program (could be functions) that keep doing their job while >other parts do something else on the same data, and what is the best >way to do this. Yes, but this is difficult. If you ask this question here, you might not be ready for this. I haven't learned it yet myself, but nevertheless tried to write a small example program quickly, which might still contain errors because of my lack of education. import threading import time def write_to_list( list, lock, event ): for i in range( 10 ): lock.acquire() try: list.append( i ) finally: lock.release() event.set() time.sleep( 3 ) def read_from_list( list, lock, event ): while True: event.wait() print( "Waking up." ) event.clear() if len( list ): print( "List contains " + str( list[ 0 ]) + "." ) lock.acquire() try: del list[ 0 ] finally: lock.release() else: print( "List is empty." ) list = [] lock = threading.Lock() event = threading.Event() threading.Thread( target=write_to_list, args=[ list, lock, event ]).start() threading.Thread( target=read_from_list, args=[ list, lock, event ]).start() In basketball, first you must learn to dribble and pass, before you can begin to shoot. With certain reservations, texts that can be considered to learn Python are: "Object-Oriented Programming in Python Documentation" - a PDF file, Introduction to Programming Using Python - Y Daniel Liang (2013), How to Think Like a Computer Scientist - Peter Wentworth (2012-08-12), The Coder's Apprentice - Pieter Spronck (2016-09-21), and Python Programming - John Zelle (2009). -- https://mail.python.org/mailman/listinfo/python-list

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Re: Parallel(?) programming with python
by Cameron Simpson Aug. 8, 2022

Aug. 8, 2022

On 08Aug2022 11:20, Stefan Ram <ram(a)zedat.fu-berlin.de> wrote: >Andreas Croci <andrea.croci(a)gmx.de> writes: >>Basically the question boils down to wether it is possible to have parts >>of a program (could be functions) that keep doing their job while other >>parts do something else on the same data, and what is the best way to do >>this. > > Yes, but this is difficult. If you ask this question here, > you might not be ready for this. This is a very standard requirement for any concurrent activity and the typical approach is a mutex (mutual exclusion). You've already hit on the "standard" approach: a `threading.Lock` object. > lock.acquire() > try: > list.append( i ) > finally: > lock.release() Small note, which makes writing this much clearer. Lock objects are context managers. So: with lock: list.append(i) is all you need. Cheers, Cameron Simpson <cs(a)cskk.id.au>

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