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

Re: Simple question - end a raw string with a single backslash ?
by Mladen Gogala Oct. 18, 2020

Oct. 18, 2020

On Thu, 15 Oct 2020 21:30:15 +0000, Stefan Ram wrote: > Tony Flury <tony.flury(a)btinternet.com> writes: >> >>> a = r'end' + chr(92) > > Or maybe, > > a = r''' > end\ > '''[ 1: -1 ] > > ? The first and the last line are messy, but in the middle, > the intended string is clearly visible. You can use perl module for python. It is installable by pip. Perl has no problems with handling backslashes. https://pypi.org/project/perl/ What you need is something like this: mgogala@umajor:~$ perl -e '$a="abcd";$a=~s/$/\\/; print "$a\n";' abcd\ Python has a problem with backslashes: Python 3.8.5 (default, Jul 28 2020, 12:59:40) [GCC 9.3.0] on linux Type "help", "copyright", "credits" or "license" for more information. >>> import re >>> a="abcd" >>> b=re.sub('$',chr(28),a) >>> b 'abcd\x1c' >>> b=re.sub('$',chr(0x41),a) >>> b 'abcdA' >>> b=re.sub('$','Z',a) >>> b 'abcdZ' >>> b=re.sub('$',chr(0x1C),a) >>> b 'abcd\x1c' >>> Any other character is shown as it should be, except backslash. -- Mladen Gogala Database Consultant http://mgogala.byethost5.com

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File Name issue
by Steve Oct. 18, 2020

Oct. 18, 2020

The line: with open("HOURLYLOG.txt", 'r') as infile: works but, when I rename the file, the line: with open("HOURLY-LOG.txt", 'r') as infile: does not. The complaint is: Cannot Assign to operator However, I have: BPM_O2s=open("BPM-O2-Readings.txt","a") And it works. At first, I thought the issue was due to having the - in the filename. Is there a fix or explanation for this? Steve FootNote: Would it be ironic if Popeye's chicken was fried in Olive Oil?

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EuroPython 2020: Edited videos are online
by M.-A. Lemburg Oct. 18, 2020

Oct. 18, 2020

We’re happy to announce that all edited videos of this year’s conference are now available on our YouTube channel: * EuroPython 2020 Playlist * https://www.youtube.com/watch?v=CvbQArKEFes&list=PL8uoeex94UhHgMD9GOCbEHWku… We have 131 videos available in total, covering a very broad set of Python topics, so there’s going to be something interesting for everyone. We hope to see you all again next year and perhaps even have a few more people attending EuroPython 2021 Online, now that the format has proven successful. Stay safe. Help spread the word -------------------- Please help us spread this message by sharing it on your social networks as widely as possible. Thank you ! Link to the blog post: https://blog.europython.eu/post/632313693115416577/europython-2020-edited-v… Tweet: https://twitter.com/europython/status/1317793661061615616 Thanks, -- EuroPython 2020 Team https://ep2020.europython.eu/ https://www.europython-society.org/

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Re: MERGE SQL in cx_Oracle executemany
by Mladen Gogala Oct. 18, 2020

Oct. 18, 2020

On Sat, 17 Oct 2020 21:23:40 -0600, Jason Friedman wrote: >> I'm looking to insert values into an oracle table (my_table) using the >> query below. The insert query works when the PROJECT is not NULL/empty >> (""). However when PROJECT is an empty string(''), the query creates a >> new duplicate row every time the code is executed (with project value >> populating as null). I would like to modify my query so a new row is >> not inserted when all column values are matched (including when project >> code is null). >> I'm guessing I would need to include a "when matched" statement, but >> not too sure on how to get this going. Would appreciate help with this, >> thanks. >> >> ``` >> con = cx_Oracle.connect(connstr) >> cur = con.cursor() >> rows = [tuple(x) for x in df.values] >> cur3.executemany('''merge into my_table using dual on (YEAR = :1 and >> QUARTER = :2 and CODE = :3 and AMOUNT = :4 and DATE = :5 and COMMENTS = >> :6 and PROJECT = :7) >> when not matched then insert values (:1, :2, :3, :4, :5, :6, :7) >> ''',rows) >> con.commit() >> cur.close() >> con.close() >> >> > Perhaps the issue is that NULL is not equal to anything. Oracle provides > the IS NULL function to determine if a value is NULL. > > Note also you define "cur" but executemany with "cur3". > > And is "rows = [tuple(x) for x in df.values]" what you want? Print it. Obviously, the "PROJECT" column is causing the issue. NULL in Oracle database is never equal to anything. If :7 is NULL, your "not matched" condition is satisfied and your MERGE statement will insert a new and exciting row. That has nothing to do with Python. The only solution is "ALTER TABLE my_table modify(project not null)" or "ALTER TABLE my_table add constraint project_nn check(project is not null)" I If you already have NULL values in the PROJECT column than use "add constraint" with NOVALIDATE option. Other than that, allowing NULL values in key columns is a sign of bad design. Namely, Oracle cannot index NULL columns, so PROJECT IS NULL predicate cannot be resolved by an index. -- Mladen Gogala Database Consultant http://mgogala.byethost5.com

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Re: File Name issue
by Mladen Gogala Oct. 18, 2020

Oct. 18, 2020

On Sat, 17 Oct 2020 18:12:16 -0400, Steve wrote: > with open("HOURLYLOG.txt", 'r') as infile: > works but, when I rename the file, the line: > with open("HOURLY-LOG.txt", 'r') as infile: > does not. The complaint is: Cannot Assign to operator Try this: with open("HOURLY\-LOG.txt", 'r') as infile: -- Mladen Gogala Database Consultant http://mgogala.byethost5.com

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MERGE SQL in cx_Oracle executemany
by Naveen Roy Vikkram Oct. 18, 2020

Oct. 18, 2020

Hi there, I'm looking to insert values into an oracle table (my_table) using the query below. The insert query works when the PROJECT is not NULL/empty (""). However when PROJECT is an empty string(''), the query creates a new duplicate row every time the code is executed (with project value populating as null). I would like to modify my query so a new row is not inserted when all column values are matched (including when project code is null). I'm guessing I would need to include a "when matched" statement, but not too sure on how to get this going. Would appreciate help with this, thanks. ``` con = cx_Oracle.connect(connstr) cur = con.cursor() rows = [tuple(x) for x in df.values] cur3.executemany('''merge into my_table using dual on (YEAR = :1 and QUARTER = :2 and CODE = :3 and AMOUNT = :4 and DATE = :5 and COMMENTS = :6 and PROJECT = :7) when not matched then insert values (:1, :2, :3, :4, :5, :6, :7) ''',rows) con.commit() cur.close() con.close() ```

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Embedding version in command-line program
by Loris Bennett Oct. 18, 2020

Oct. 18, 2020

Hi, I have written a program, which I can run on the command-line thus mypyprog --version and the get the version, which is currently derived from a variable in the main module file. However, I also have the version in an __init__.py file and in a pyproject.toml (as I'm using poetry, otherwise this would be in setup.py). What's the best way of reducing these three places where the version is defined to a single one? Cheers, Loris -- This signature is currently under construction.

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Re: File Name issue
by shrimp_banana Oct. 18, 2020

Oct. 18, 2020

On 10/17/20 4:12 PM, Steve wrote: > The line: > with open("HOURLYLOG.txt", 'r') as infile: > works but, when I rename the file, the line: > with open("HOURLY-LOG.txt", 'r') as infile: > does not. The complaint is: Cannot Assign to operator > > However, I have: > BPM_O2s=open("BPM-O2-Readings.txt","a") > And it works. > > At first, I thought the issue was due to having the - in the filename. > > Is there a fix or explanation for this? > Steve I am unsure if this will help but you could try putting an r in front of the quotes to make it take raw data only. ie. with open(r"HOURLY-LOG.txt", 'r') as infile

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Re: Subprocess Connection Error
by Greg Ewing Oct. 18, 2020

Oct. 18, 2020

On 17/10/20 4:04 pm, Dave Dungan wrote: > One more thing, the book says to save it as "types.py". Which is probably a bad thing to do, because there is a built-in module called "types" that this will shadow. If IDLE happens to use that module, bad things could happen. Have you tried using a different name, such as "my_types.py"? -- Greg

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Subprocess Connection Error
by Dave Dungan Oct. 17, 2020

Oct. 17, 2020

Hello, I bought a book called Coding for Beginners to learn how to code using Python. The first few exercises went fine. When I got to the page called Recognizing types and did the exercise and saved it and tried to run the module it comes up with a Subprocess Connection Error. It says, "IDLE's subprocess didn't make connection. See the Start up failure section of the IDLE doc, online at https://docs.python.org/3/library/idle.html#startup-failure." I went there and it said to try uninstalling python and then reinstalling it. I did this and it did the same thing again. It also said something about it is because of the antivirus software. I tried installing python on a different computer and it happened at the exact same place in the exercises in the book. I am far from being a computer whiz, just thought it would be fun to learn some simple coding. Any help would be appreciated. One more thing, the book says to save it as "types.py". Thank you, Dave Dungan

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