🌐 Mailman 3 May 2020 - Python-list - python.org

Re: Strings: double versus single quotes
by Tim Chase May 23, 2020

May 23, 2020

On 2020-05-23 14:46, Dennis Lee Bieber wrote: > On Sat, 23 May 2020 11:03:09 -0500, Tim Chase > >But when a string contains both, it biases towards single quotes: > > > > >>> "You said \"No it doesn't\"" > > 'You said "No it doesn\'t"' > > This is where using triple quotes (or triple apostrophes) > around the entire thing simplifies it all... (except for a need to > separate the four ending quotes) Unless you're pathological. ;-) >>> """I said "This contain every type of \"""Python\""" '''triple-quoted''' string, doesn't it?\"""" 'I said "This contains every type of """Python""" \'\'\'triple-quoted\'\'\' string, doesn\'t it."' And-you-can-quote-me-on-that'ly yers, -tkc

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Enums are Singletons - but not always?
by Ralf M. May 23, 2020

May 23, 2020

Hello, recently I wrote a small library that uses an Enum. That worked as expected. Then I added a main() and if __name__ == "__main__" to make it runable as script. Now Enum members that should be the same aren't identical any more, there seem to be two instances of the same Enum. I think I know what's going on, but cannot find a good and elegant way to avoid the problem. I hope someone here can help me there. Below are a simplified code sample, the results when I run it and my thoughts. ##### Code of mod1.py ##### import enum, mod2 class En(enum.Enum): A = 1 B = 2 def main(): a = mod2.getA() print("a is En.A:", a is En.A) print("a:", repr(a), " En.A:", repr(En.A)) print("id(a), id(a.__class__)", id(a), id(a.__class__)) print("id(En.A), id(En) ", id(En.A), id(En)) if __name__ == "__main__": main() ##### End of mod1.py ##### ##### Code of mod2.py ##### import mod1 def getA(): return mod1.En.A ##### End of mod2.py ##### ##### Results when run: ##### C:\tmp>py mod1.py a is En.A: False a: <En.A: 1> En.A: <En.A: 1> id(a), id(a.__class__) 33305864 7182808 id(En.A), id(En) 33180552 7183752 C:\tmp>py Python 3.7.4 (tags/v3.7.4:e09359112e, Jul 8 2019, 20:34:20) [MSC v.1916 64 bit (AMD64)] on win32 Type "help", "copyright", "credits" or "license" for more information. >>> import mod1 >>> mod1.main() a is En.A: True a: <En.A: 1> En.A: <En.A: 1> id(a), id(a.__class__) 49566792 44574280 id(En.A), id(En) 49566792 44574280 >>> So: When run as script there are two instances of En (different ids), but when mod1 is imported and mod1.main() is run it works as expected (just one instance of En, same ids). BTW: py -m mod1 doesn't work either. What I thing is happening: When the script is run, mod1.py is executed and an instance of En and its members is created. During the same run mod1 is also imported (via mod2), the file mod1.py is executed again as part of the import and another, different instance of En and its members is created. How do I have to change mod1.py to avoid the problem? Currently I have moved main() into a new file script.py. That works, but is not what I wanted. I doubt it's a bug in the enum module, but should that be the case, I'm willing to open an issue on the bug tracker. Or can nothing be done about it? Looking forward to any ideas Ralf M. P.S.: As I was about to send this post the following modification occured to me (see below). It works, but it doesn't feel right to import a module directly from inside itself. ##### Modified code of mod1.py (one line added) ##### import enum, mod2 class En(enum.Enum): A = 1 B = 2 from mod1 import En # NEW LINE, overwrite just defined En def main(): a = mod2.getA() print("a is En.A:", a is En.A) print("a:", repr(a), " En.A:", repr(En.A)) print("id(a), id(a.__class__)", id(a), id(a.__class__)) print("id(En.A), id(En) ", id(En.A), id(En)) if __name__ == "__main__": main()

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Fwd: installed but doesn't boot
by Ben Hansen May 23, 2020

May 23, 2020

---------- Forwarded message --------- From: Ben Hansen <benhansen1945(a)gmail.com> Date: Sat, May 23, 2020 at 11:44 AM Subject: Fwd: installed but doesn't boot To: <python-list(a)python.org> ---------- Forwarded message --------- From: Ben Hansen <benhansen1945(a)gmail.com> Date: Fri, May 22, 2020 at 3:18 PM Subject: installed but doesn't boot To: <python-list(a)python.org> I have installed python after getting the book "Coding for Kids/Python, and it won't boot. HELP1111

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Subject: Python Open-Source Snippets Newsletter
by Aswin K May 23, 2020

May 23, 2020

Hi, I am creating a Python newsletter showcasing useful code snippets from popular open-source libraries. I will also be providing a runnable demo link to better understand the working. Newsletter subscription link: https://www.pythonninja.xyz/subscribe A sample snippet from the newsletter: HTTP Request retrying with Backoffs - Technique for retrying failed HTTP requests. From Google Maps Services Python (https://github.com/googlemaps/google-maps-services-python) Demo link: https://repl.it/@PythonNinja/requestretries """ first_request_time: The time of the first request (None if no retries have occurred). retry_counter: The count of retries, or zero for the first attempt. """ if not first_request_time: first_request_time = datetime.now() elapsed = datetime.now() - first_request_time if elapsed > self.retry_timeout: raise googlemaps.exceptions.Timeout() if retry_counter > 0: # 0.5 * (1.5 ^ i) is an increased sleep time of 1.5x per iteration, # starting at 0.5s when retry_counter=0. The first retry will occur # at 1, so subtract that first. delay_seconds = 0.5 * 1.5 ** (retry_counter - 1) # Jitter this value by 50% and pause. time.sleep(delay_seconds * (random.random() + 0.5)) Subscribe here: https://www.pythonninja.xyz/subscribe Feedbacks and criticism are welcome.

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How to design a class that will listen on stdin?
by zljubisic＠gmail.com May 23, 2020

May 23, 2020

Hi, I have to talk to outer system by stdin/stdout. Each line that comes to stdin should be processed and its result returned back to stdout. Logging should go to stderr. How to design a class that will listed to stdin and call required methods in order to process the data? Regards

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exiting a while loop
by John Yeadon May 23, 2020

May 23, 2020

Am I unreasonable in expecting this code to exit when required? # Add up the powers of 2 starting with 2**0 until 2 million is met. n = 1 target = 2000000 sum = 0 while True: x = 2 ** (n - 1) sum += x print(n, sum) if sum >= target: print("Target met.") exit n += 1 print("\n", n, "terms are required.")

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FlaskCon Call For Papers
by Abdur-Rahmaan Janhangeer May 23, 2020

May 23, 2020

Greetings list, The call for papers for FlaskCon is open: https://flaskcon.com/ It is a community-run event, 100% free and remote with reviewers from the Pallets, Flask maintainers and more Feel free to pass the word around! Kind Regards, Abdur-Rahmaan Janhangeer Mauritius

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Re: Strings: double versus single quotes
by Manfred Lotz May 23, 2020

May 23, 2020

On Tue, 19 May 2020 13:36:54 -0500 Tim Chase <python.list(a)tim.thechases.com> wrote: > On 2020-05-19 20:10, Manfred Lotz wrote: > > Hi there, > > I am asking myself if I should preferably use single or double > > quotes for strings? > > I'd say your consistency matters more than which one you choose. > First, thanks to all for your opinions and judgements. I agree to the following: 1. Consistency is important. 2. Single quotes are less noisy. 3. Triple double quotes are to be preferred over triple single quotes. I also believe that transferring habits from C, Rust or whatever to Python doesn't make much sense as Python does not distinguish between a character and string from a type perspective. Of course, this is my subjective result, and others (may) have different opinions. -- Manfred

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PyCharm, how to setup self contained subprojects
by zljubisic＠gmail.com May 23, 2020

May 23, 2020

Hi, I should provide python code for (Spring) microservice patform. In microservice paradigm, each microservice should do a simple task, so python code beneath it should be very small. As a PyCharm (community) user, I don't know how to set up such development environment. Each microservice could be a separate PyCharm project, but these projects should share some common classes. For example, let's say that you have a class for communication with outer world. Each PyCharm project (microservice) should use instance of this class, and do the different things with its data. I would like to avoid coping this common object to each PyCharm project (and prevent refactoring). Another, requirement is deployment of PyCharm project to the microservice platform. At the moment, my each microservice code is in separate project. I am coping each project files on separate folder on deployment server. So, each PyCharm project has its own main.py (the name of main.py can be different for each microservice). On deployment servers I cannot install anything. Another approach would be to have single PyCharm project with many root directories for microservices and multiple main.py files. In this case, when I deploy a single microservice, I will have trouble finding out what files I should copy (common classes), or to copy everything from PyCharm project, but specify main.py for specific microservice (root). If anyone is in the same situation, please share how you have set up PyCharm for such purpose, and how you are doing development. Regards

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Re: Strings: double versus single quotes
by Manfred Lotz May 22, 2020

May 22, 2020

On Sat, 23 May 2020 09:36:13 +1200 DL Neil <PythonList(a)DancesWithMice.info> wrote: > >>> I am asking myself if I should preferably use single or double > >>> quotes for strings? > ... > > > I agree to the following: > > > > 1. Consistency is important. > > 2. Single quotes are less noisy. > > 3. Triple double quotes are to be preferred over triple single > > quotes. > ... > > > Of course, this is my subjective result, and others (may) have > > different opinions. > > 4. unless a specific objective of a re-factoring exercise, maintain > the conventions used within the code. > > 5, adhere to the conventions/standards/requirements of the dev.team > or organisation. > Yes, agree. -- Manfred

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