🌐 Mailman 3 December 2021 - Python-list - python.org

Re: recover pickled data: pickle data was truncated
by iMath Jan. 2, 2022

Jan. 2, 2022

在 2021年12月30日星期四 UTC+8 03:13:21，<Marco Sulla> 写道： > On Wed, 29 Dec 2021 at 18:33, iMath <redsto...(a)163.com> wrote: > > But I found the size of the file of the shelve data didn't change much, so I guess the data are still in it , I just wonder any way to recover my data. > I agree with Barry, Chris and Avi. IMHO your data is lost. Unpickling > it by hand is a harsh work and maybe unreliable. > > Is there any reason you can't simply add a semaphore to avoid writing > at the same time and re-run the code and regenerate the data? Thanks for your replies! I didn't have a sense of adding a semaphore on writing to pickle data before, so corrupted the data. Since my data was colleted in the daily usage, so cannot re-run the code and regenerate the data. In order to avoid corrupting my data again and the complicity of using a semaphore, now I am using json text to store my data.

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How to implement freelists in dict 3.10 for previous versions?
by Marco Sulla Jan. 1, 2022

Jan. 1, 2022

I noticed that now freelists in dict use _Py_dict_state. I suppose this is done for thread safety. I would implement it also for a C extension that uses CPython < 3.10. How can I achieve this?

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using OpenGL on windows 11
by vrg bls Jan. 1, 2022

Jan. 1, 2022

Hi! I am very new to Python admittedly, but did try several options regarding troubleshooting to get OpenGL to run with Python. I am using PyCharm as my interface, did try installing setup tools and have reinstalled using pip install function a few times. I did notice my machine seems to be having trouble remembering that I did install python and keeps prompting me to install from MS app store. I did try to do this but again did not register the installation of Python. I am able to open a window in PyCharm and get other functions to work but then get the Module not Installed error for OpenGL. I even tried the setuptools install and easy_install never popped up as an option. is this a windows 11 issue? does anything about this sound familiar? Thank you, and sorry if this has already been answered in a forum somewhere, I did look and could not find it -- Virginia Bliss virginia.a.bliss(a)gmail.com 678 640 1902 Los Angeles. CA

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Re: builtins.TypeError: catching classes that do not inherit from BaseException is not allowed
by hongy...＠gmail.com Jan. 1, 2022

Jan. 1, 2022

On Friday, December 31, 2021 at 7:50:48 AM UTC+8, MRAB wrote: > On 2021-12-30 23:27, hongy...(a)gmail.com wrote: > > On Friday, December 31, 2021 at 7:04:24 AM UTC+8, Chris Angelico wrote: > >> Neither of these wants to be recursive, and writing them recursively > >> pollutes the function signature with parameters that really exist just > >> to be local variables. Passing an accumulator down is a terrible way > >> to demonstrate the beauty of recursion - it instead shows off how you > >> can shoehorn anything into recursion and make it worse in the process. > > > > Then what cases/scenarios can demonstrate the beauty of recursion? > > > Walking a tree. There are many type of trees. Do you mean all of them?

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Re: builtins.TypeError: catching classes that do not inherit from BaseException is not allowed
by hongy...＠gmail.com Dec. 31, 2021

Dec. 31, 2021

On Friday, December 31, 2021 at 4:18:28 PM UTC+8, Marco Sulla wrote: > It was already done: https://pypi.org/project/tail-recursive/ A few days ago, I also noticed another similar project: https://github.com/baruchel/tco It seems that they are very similar, even identical. But I'm not sure, so I filed an issue here [1]. [1] https://github.com/0scarB/tail-recursive/issues/1

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builtins.TypeError: catching classes that do not inherit from BaseException is not allowed
by hongy...＠gmail.com Dec. 31, 2021

Dec. 31, 2021

I try to compute the factorial of a large number with tail-recursion optimization decorator in Python3. The following code snippet is converted from the code snippet given here [1] by the following steps: $ pyenv shell datasci $ python --version Python 3.9.1 $ pip install 2to3 $ 2to3 -w this-script.py ``` # This program shows off a python decorator( # which implements tail call optimization. It # does this by throwing an exception if it is # its own grandparent, and catching such # exceptions to recall the stack. import sys class TailRecurseException: def __init__(self, args, kwargs): self.args = args self.kwargs = kwargs def tail_call_optimized(g): """ This function decorates a function with tail call optimization. It does this by throwing an exception if it is its own grandparent, and catching such exceptions to fake the tail call optimization. This function fails if the decorated function recurses in a non-tail context. """ def func(*args, **kwargs): f = sys._getframe() if f.f_back and f.f_back.f_back \ and f.f_back.f_back.f_code == f.f_code: raise TailRecurseException(args, kwargs) else: while 1: try: return g(*args, **kwargs) except TailRecurseException as e: args = e.args kwargs = e.kwargs func.__doc__ = g.__doc__ return func @tail_call_optimized def factorial(n, acc=1): "calculate a factorial" if n == 0: return acc return factorial(n-1, n*acc) print(factorial(10000)) # prints a big, big number, # but doesn't hit the recursion limit. @tail_call_optimized def fib(i, current = 0, next = 1): if i == 0: return current else: return fib(i - 1, next, current + next) print(fib(10000)) # also prints a big number, # but doesn't hit the recursion limit. ``` However, when I try to test the above script, the following error will be triggered: ``` $ python this-script.py Traceback (most recent call last): File "/home/werner/this-script.py", line 32, in func return g(*args, **kwargs) File "/home/werner/this-script.py", line 44, in factorial return factorial(n-1, n*acc) File "/home/werner/this-script.py", line 28, in func raise TailRecurseException(args, kwargs) TypeError: exceptions must derive from BaseException During handling of the above exception, another exception occurred: Traceback (most recent call last): File "/home/werner/this-script.py", line 46, in <module> print(factorial(10000)) File "/home/werner/this-script.py", line 33, in func except TailRecurseException as e: TypeError: catching classes that do not inherit from BaseException is not allowed ``` Any hints for fixing this problem will be highly appreciated. [1] https://stackoverflow.com/q/27417874 Regards, HZ

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Re: builtins.TypeError: catching classes that do not inherit from BaseException is not allowed
by hongy...＠gmail.com Dec. 31, 2021

Dec. 31, 2021

On Friday, December 31, 2021 at 7:04:24 AM UTC+8, Chris Angelico wrote: > Neither of these wants to be recursive, and writing them recursively > pollutes the function signature with parameters that really exist just > to be local variables. Passing an accumulator down is a terrible way > to demonstrate the beauty of recursion - it instead shows off how you > can shoehorn anything into recursion and make it worse in the process. Then what cases/scenarios can demonstrate the beauty of recursion? HZ

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Re: builtins.TypeError: catching classes that do not inherit from BaseException is not allowed
by hongy...＠gmail.com Dec. 30, 2021

Dec. 30, 2021

On Thursday, December 30, 2021 at 11:23:35 PM UTC+8, Chris Angelico wrote: > If it's an exception, it needs to subclass Exception or BaseException. I see. That is, the following: class TailRecurseException(Exception): def __init__(self, args, kwargs): self.args = args self.kwargs = kwargs > (Also, is this REALLY an optimization? Exception handling isn't the > fastest. Yes, it avoids some measure of recursion depth, but it looks > like a pretty inefficient way to do things. Python is not Lisp, and > there are very very few algorithms that actually benefit from tail > call optimization that wouldn't benefit far more from other ways of > doing the same thing.) Could you give some examples of the other methods you mentioned above? > ChrisA HZ

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Re: builtins.TypeError: catching classes that do not inherit from BaseException is not allowed
by hongy...＠gmail.com Dec. 30, 2021

Dec. 30, 2021

On Thursday, December 30, 2021 at 11:24:20 PM UTC+8, Chris Angelico wrote: > On Fri, Dec 31, 2021 at 2:03 AM hongy...(a)gmail.com > <hongy...(a)gmail.com> wrote: > > See here [1] for the related discussion. > > > > [1] https://discuss.python.org/t/typeerror-catching-classes-that-do-not-inherit… > Why did you post in two places at once? Did you need more people to > tell you the same thing as the error message? Doing so may attract the attention of developers, such as increasing the content of traceback information to make troubleshooting easier, just as André Roberge says here [1]. [1] https://discuss.python.org/t/typeerror-catching-classes-that-do-not-inherit… > ChrisA HZ

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Re: recover pickled data: pickle data was truncated
by iMath Dec. 29, 2021

Dec. 29, 2021

> You have lost the data in that case. But I found the size of the file of the shelve data didn't change much, so I guess the data are still in it , I just wonder any way to recover my data.

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