🌐 Mailman 3 May 2023 - Python-list - python.org

Re: Does os.path relpath produce an incorrect relative path?
by BlindAnagram May 27, 2023

May 27, 2023

On 26/05/2023 16:42, Eryk Sun wrote: > On 5/26/23, cactus <riemannic(a)gmail.com> wrote: >> >> Surprisingly (for me at least) the alternative provided by the pathlib >> module 'relative_to' method doesn't provide for full relative path >> computation. I was expecting this would offer everything that os.path >> offers but it doesn't in this case. > > Starting with Python 3.12, the relative_to() method has a walk_up > parameter. It defaults to False for the sake of backward > compatibility. > > https://docs.python.org/3.12/library/pathlib.html#pathlib.PurePath.relative… Thanks, it is good to know that this is coming. Brian

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"Invalid literal for int() with base 10": is it really a literal?
by Roel Schroeven May 27, 2023

May 27, 2023

Kevin M. Wilson's post "Invalid literal for int() with base 10?" got me thinking about the use of the word "literal" in that message. Is it correct to use "literal" in that context? It's correct in something like this: >>> int('invalid') Traceback (most recent call last): File "<stdin>", line 1, in <module> ValueError: invalid literal for int() with base 10: 'invalid' But something like this generates the same message: >>> int(input()) hello Traceback (most recent call last): File "<stdin>", line 1, in <module> ValueError: invalid literal for int() with base 10: 'hello' In cases like this there is no literal in sight. I'm thinking it would be more correct to use the term 'value' here: ValueError: invalid value for int() with base 10: 'hello' Does my reasoning make sense? -- "I love science, and it pains me to think that to so many are terrified of the subject or feel that choosing science means you cannot also choose compassion, or the arts, or be awed by nature. Science is not meant to cure us of mystery, but to reinvent and reinvigorate it." -- Robert Sapolsky

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Module error
by giuseppacefalu＠gmail.com May 27, 2023

May 27, 2023

I have reinstalled python which reinstalls pip. I have added the path:'C:\sers\Giuseppa\AppData\Local\Packages\PythonSoftwareFoundation.Pytho n.3.11_qbz5n2kfra8p0\LocalCache\local-packages\Python311\Scripts and still get the error below. Could you help me with this please? Traceback (most recent call last): File "C:\Users\Giuseppa\Documents\DataScience\PYTHON\Subsetting.py", line 11, in <module> import pandas as pd ModuleNotFoundError: No module named 'pandas' Thank you!No

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Re: Does os.path relpath produce an incorrect relative path?
by cactus May 26, 2023

May 26, 2023

On Thursday, 25 May 2023 at 17:57:21 UTC+1, MRAB wrote: > On 2023-05-25 16:53, Eryk Sun wrote: > > On 5/25/23, BlindAnagram <BlindA...(a)nowhere.org> wrote: > >> > >> vcx_path = 'C:\\build.vs22\\lib\\lib.vcxproj' > >> src_path = 'C:\\lib\\src\\' > >> rel_path = '..\\..\\..\\lib\\src' > >> > >> [snip] > >> > >> The first of these three results produces an incorrect relative path > >> because relpath does not strip off any non-directory tails before > >> comparing paths. > > > > The start path is assumed to be a directory, which defaults to the > > current working directory, and the input paths are first resolved as > > absolute paths. In order to reach src_path from vcx_path, one has to > > traverse 3 levels up to the root directory. > > > > https://docs.python.org/3/library/os.path.html#os.path.relpath > Well, it's not necessarily the optimal relative path, because it's not > always necessary to go all the way up to the root, as in the first example. Thanks to all for their comments. I was hoping that there would be an direct way in Python to find a relative path between two paths in which the convention is that all directories end with '\\' so that it is possible to distinguish the 'tail' references to files as not part of the path comparison. But I will just have to remember to strip the file tails myself. Surprisingly (for me at least) the alternative provided by the pathlib module 'relative_to' method doesn't provide for full relative path computation. I was expecting this would offer everything that os.path offers but it doesn't in this case. Brian

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Invalid literal for int() with base 10?
by Kevin M. Wilson May 26, 2023

May 26, 2023

Ok, I'm not finding any info. on the int() for converting a str to an int (that specifies a base parameter)?! The picture is of the code I've written... And the base 10 paradigm involved?? years = int('y') # store for calculationValueError: invalid literal for int() with base 10: 'y'What is meant by "invalid literal"? I'm trying to convert srt to int, and I didn't know I needed to specify the base. Plus I haven't read anything that I need to specify the base for the int(). Attached is the code, showing the code and the execution of said code. "When you pass through the waters, I will be with you: and when you pass through the rivers, they will not sweep over you. When you walk through the fire, you will not be burned: the flames will not set you ablaze." Isaiah 43:2

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Re: Invalid literal for int() with base 10?
by Keith Thompson May 26, 2023

May 26, 2023

"Kevin M. Wilson" <kevinmwilson1956(a)yahoo.com> writes: > Ok, I'm not finding any info. on the int() for converting a str to an > int (that specifies a base parameter)?! https://docs.python.org/3/library/functions.html#int > The picture is of the code I've written... I don't see a picture. The mailing list probably does not accept attachments. (You don't need a picture anyway.) > And the base 10 paradigm involved?? The int() constructor takes a base parameter whose default value is 10. If you specify base=0, it will accept binary, octal, and hexadecimal numbers in addition to decimal. All this is explained in the link I gave you. > years = int('y') # store for calculationValueError: invalid > literal for int() with base 10: 'y'What is meant by "invalid literal"? '42' is a valid literal for int(). 'y' is not. What value did you expect int('y') to give you? Perhaps you have a variable named 'y' containing a string? If so, you might want something like int(y) or int(f{'y'}), but int('y') passes the literal string 'y', which has nothing to do with a variable of that name. > I'm trying to convert srt to int, Do you mean "str to int"? > and I didn't know I needed to specify the base. You don't. If you don't specify the base, it defaults to 10. > Plus I haven't read anything that I need to specify > the base for the int(). Attached is the code, showing the code and > the execution of said code. Any attachment was removed. > "When you pass through the waters, I will > be with you: and when you pass through the rivers, they will not sweep > over you. When you walk through the fire, you will not be burned: the > flames will not set you ablaze." Isaiah 43:2 You can add a signature to all your messages if you like, but it will be very helpful if you introduce it with a line consisting of "-- ", as I've done here. It would also be very helpful if you introduce line breaks into your message, particularly before and after any included code. The formatting made your message difficult to read. -- Keith Thompson (The_Other_Keith) Keith.S.Thompson+u(a)gmail.com Will write code for food. void Void(void) { Void(); } /* The recursive call of the void */

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From geeksforgeeks.org, on converting the string created by the input() to an INT
by Kevin M. Wilson May 26, 2023

May 26, 2023

We can first convert the string representation of float into float using float() function and then convert it into an integer using int().So, why can't a string of an integer be converted to an integer, via print(int(str('23.5')))??? Perplexed | print(int(float('23.5'))) | "When you pass through the waters, I will be with you: and when you pass through the rivers, they will not sweep over you. When you walk through the fire, you will not be burned: the flames will not set you ablaze." Isaiah 43:2

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Does os.path relpath produce an incorrect relative path?
by BlindAnagram May 25, 2023

May 25, 2023

I am wondering whether I have misunderstood the semantics of os.path relpath or whether it has a bug. Here is a short test program: ----------------------------------------------------------- from os.path import relpath, split src_path = 'C:\\lib\\src\\' vcx_path = 'C:\\build.vs22\\lib\\lib.vcxproj' rel_path = relpath(src_path, vcx_path) print(f"{vcx_path = }\n{src_path = }\n{rel_path = }\n") vcx_path = 'C:\\build.vs22\\lib\\' rel_path = relpath(src_path, vcx_path) print(f"{vcx_path = }\n{src_path = }\n{rel_path = }\n") vcx_path = 'C:\\build.vs22\\lib\\lib.vcxproj' rel_path = relpath(src_path, split(vcx_path)[0]) print(f"{vcx_path = }\n{src_path = }\n{rel_path = }\n") ----------------------------------------------------------- and its output with Python 3.11: ----------------------------------------------------------- vcx_path = 'C:\\build.vs22\\lib\\lib.vcxproj' src_path = 'C:\\lib\\src\\' rel_path = '..\\..\\..\\lib\\src' vcx_path = 'C:\\build.vs22\\lib\\' src_path = 'C:\\lib\\src\\' rel_path = '..\\..\\lib\\src' vcx_path = 'C:\\build.vs22\\lib\\lib.vcxproj' src_path = 'C:\\lib\\src\\' rel_path = '..\\..\\lib\\src' ----------------------------------------------------------- The first of these three results produces an incorrect relative path because relpath does not strip off any non-directory tails before comparing paths. Is this a bug or my misunderstanding of relpath semantics? Comments would be appreciated as I don't waste developer time if this is not a bug. regards Brian

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[RELEASE] Python 3.12.0 beta 1 released.
by Thomas Wouters May 25, 2023

May 25, 2023

I'm pleased to announce the release of Python 3.12 beta 1 (and feature freeze for Python 3.12). https://www.python.org/downloads/release/python-3120b1/ This is a beta preview of Python 3.12 Python 3.12 is still in development. This release, 3.12.0b1, is the first of four planned beta release previews of 3.12. Beta release previews are intended to give the wider community the opportunity to test new features and bug fixes and to prepare their projects to support the new feature release. We strongly encourage maintainers of third-party Python projects to test with 3.12 during the beta phase and report issues found to [the Python bug tracker (Issues · python/cpython · GitHub) as soon as possible. While the release is planned to be feature complete entering the beta phase, it is possible that features may be modified or, in rare cases, deleted up until the start of the release candidate phase (Monday, 2023-07-31). Our goal is to have no ABI changes after beta 4 and as few code changes as possible after 3.12.0rc1, the first release candidate. To achieve that, it will be extremely important to get as much exposure for 3.12 as possible during the beta phase. Please keep in mind that this is a preview release and its use is not recommended for production environments. Major new features of the 3.12 series, compared to 3.11 Some of the new major new features and changes in Python 3.12 are: - New type annotation syntax for generic classes (PEP 695 <https://peps.python.org/pep-0695/>). - More flexible f-string parsing, allowing many things previously disallowed (PEP 701 <https://peps.python.org/pep-0701/>). - Even more improved error messages. More exceptions potentially caused by typos now make suggestions to the user. - Many large and small performance improvements (like PEP 709 <https://peps.python.org/pep-0709/>). - Support for the Linux perf profiler to report Python function names in traces. - The deprecated wstr and wstr_length members of the C implementation of unicode objects were removed, per PEP 623 <https://peps.python.org/pep-0623/>. - In the unittest module, a number of long deprecated methods and classes were removed. (They had been deprecated since Python 3.1 or 3.2). - The deprecated smtpd and distutils modules have been removed (see PEP 594 <https://peps.python.org/pep-0594/> and PEP 632 <https://peps.python.org/pep-0632/>. The setuptools package (installed by default in virtualenvs and many other places) continues to provide the distutils module. - A number of other old, broken and deprecated functions, classes and methods have been removed. - Invalid backslash escape sequences in strings now warn with SyntaxWarning instead of DeprecationWarning, making them more visible. (They will become syntax errors in the future.) - The internal representation of integers has changed in preparation for performance enhancements. (This should not affect most users as it is an internal detail, but it may cause problems for Cython-generated code.) - (Hey, fellow core developer, if a feature you find important is missing from this list, let Thomas know <thomas(a)python.org>.) For more details on the changes to Python 3.12, see What’s new in Python 3.12 <https://docs.python.org/dev/whatsnew/3.12.html>. The next pre-release of Python 3.12 will be 3.12.0b2, currently scheduled for 2023-05-29. More resources Online Documentation <https://docs.python.org/3.12/>. PEP 693 <https://www.python.org/dev/peps/pep-0693/>, the Python 3.12 Release Schedule. Report bugs via GitHub Issues <https://github.com/python/cpython/issues>. Help fund Python and its community <https://www.python.org/psf/donations/>. And now for something completely different As the first beta release marks the point at which we fork off the release branch from the main development branch, here’s a poem about forks in the road. Two roads diverged in a yellow wood, And sorry I could not travel both And be one traveler, long I stood And looked down one as far as I could To where it bent in the undergrowth; Then took the other, as just as fair, And having perhaps the better claim, Because it was grassy and wanted wear; Though as for that the passing there Had worn them really about the same, And both that morning equally lay In leaves, no step had trodden black. Oh, I kept the first for another day! Yet knowing how way leads on to way, I doubted if I should ever come back. I shall be telling this with a sigh Somewhere ages and ages hence: Two roads diverged in a wood, and I — I took the one less traveled by, And that has made all the difference. *The Road Not Taken*, by Robert Frost. Enjoy the new release Thanks to all of the many volunteers who help make Python Development and these releases possible! Please consider supporting our efforts by volunteering yourself or through organization contributions to the Python Software Foundation. Your release team, Thomas Wouters Ned Deily Steve Dower -- Thomas Wouters <thomas(a)python.org>

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getting rid of the recursion in __getattribute__
by A KR May 25, 2023

May 25, 2023

It is perfectly explained in the standards here [1] saying that: <quote> In order to avoid infinite recursion in this method, its implementation should always call the base class method with the same name to access any attributes it needs, for example, object.__getattribute__(self, name). </quote> Therefore, I wrote a code following what the standard says: <code> class Sample(): def __init__(self): self.a = -10 def __getattribute__(self, name): if name == 'a': return object.__getattribute__(self, name) raise AttributeError() s = Sample() result = s.a print(result) </code> I did not fall into recursion, and the output was -10 I used here object.__getattribute__(self, name) cause the base class of Sample is object. If I derive the Sample class from another class such as A, I should change object.__getattribute__(self, name) to A.__getattribute__(self, name) as the base class of class Sample is class A. <code> class A: pass class Sample(A): def __init__(self): self.a = -10 def __getattribute__(self, name): if name == 'a': return A.__getattribute__(self, name) raise AttributeError() s = Sample() result = s.a print(result) </code> which gives the same output as expected. No recursion and -10. However, when I try the code without deriving from a class: class AnyClassNoRelation: pass class Sample(): def __init__(self): self.a = -10 def __getattribute__(self, name): if name == 'a': return AnyClassNoRelation.__getattribute__(self, name) raise AttributeError() s = Sample() result = s.a print(result) and calling __getattribute__ via any class (in this example class AnyClassNoRelation) instead of object.__getattribute__(self, name) as the standard says call using the base class, I get the same output: no recursion and -10. So my question: How come this is possible (having the same output without using the base class's __getattribute__? Although the standards clearly states that __getattribute__ should be called from the base class. <quote> In order to avoid infinite recursion in this method, its implementation should always call the base class method with the same name to access any attributes it needs, for example, object.__getattribute__(self, name). </quote> Literally, I can call __getattribute__ with anyclass (except Sample cause it will be infinite recursion) I define and it works just fine. Could you explain me why that happens? [1] https://docs.python.org/3/reference/datamodel.html#object.__getattribute__

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