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

creating a table within python code
by Buddy Peacock May 28, 2020

May 28, 2020

I'm working on my first python project in CS50W and I am trying to create 2 tables. I am getting the following error when trying to run it: I have included my code below the error message. flask.cli.NoAppException: Failed to find Flask application or factory in module "create_db". Use "FLASK_APP=create_db:name to specify one. Traceback (most recent call last) File "C:\Users\buddy\AppData\Local\Programs\Python\Python38\Lib\site-packages\flask\_compat.py", line 39, in reraise raise value File "C:\Users\buddy\AppData\Local\Programs\Python\Python38\Lib\site-packages\flask\cli.py", line 97, in find_best_app raise NoAppException( flask.cli.NoAppException: Failed to find Flask application or factory in module "create_db". Use "FLASK_APP=create_db:name to specify one. I used: FLASK_APP=create_db.py at the command line and this is my code: import os from flask import Flask, session from flask_session import Session from sqlalchemy import create_engine from sqlalchemy.orm import scoped_session, sessionmaker engine = create_engine(os.getenv("DATABASE_URL")) db = scoped_session(sessionmaker(bind=engine)) def main(): db.execute("CREATE TABLE books (id SERIAL PRIMARY KEY, isbn VARCHAR NOT NULL, title VARCHAR NOT NULL, author INTEGER NOT NULL, year INTEGER NOT NULL,)") db.execute("CREATE TABLE authors (id SERIAL PRIMARY KEY, name VARCHAR NOT NULL,)") db.commit() if __name__ == "__main__": main() Does anyone have any ideas? Al (Buddy) Peacock, PMP, MCCT, ITILv3, SMC, CSM, SPOC (920) 740-3411 linkedin.com/in/buddypeacock <https://www.linkedin.com/in/buddypeacock/>

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Re: why no camelCase in PEP 8?
by Eli the Bearded May 28, 2020

May 28, 2020

In comp.lang.python, Paul Rubin <no.email(a)nospam.invalid> wrote: > I don't know if this was the explicit motivation for PEP 8, but it > has always seemed valid to me: > > https://en.wikipedia.org/wiki/Camel_case#Readability_studies There are three things cited there. One is a NYTimes story from 2009 "Against Camel Case" starting out with criticism of "iPhone" which the author describes but won't use as it it too difiguring. That's not a programmer talking about program identifiers. The other two are more relevant, two studies one from 2009 and one from 2010, each of which seems to reach a conclusion at odds with the other. The 2009 one finds camelCase easier to read than snake_case, and the 2010 one finds people recognize snake_case identifiers faster than camelCase ones. I don't think that Wikipedia page helps your case. I personally abhor the use of inappropriate mid-word caps in English, which fits the NYT piece, but am only mildly against them in code. I had some bad expierences with code that forced use of capital letters in college and that has tainted me against excess capitals ever since. This is a highly personal reason that I don't expect anyone else to share. Here's a simple argument against camel case: when it becomes necessary to join identifiers, camel case requires modification of the original unit while snake case just adds stuff to beginning and/or end. One noteworthy example is when a negated version is needed. camelCase -> noCamelCase snake_case -> no_snake_case One of those is easier to "grep" for than the other. Elijah ------ grep-ability of code should on everyone's mond

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SQLAlchemy & Postgresql
by Buddy Peacock May 28, 2020

May 28, 2020

Hello group, I have a pretty good background in MySQL & MSSQL as well as VB & Php, but I am new to Python and Postgresql. I am taking a class and working on a project to insert authors and books into a table. My code for this is: =============================================================== import csv import os from flask import Flask from sqlalchemy import create_engine from sqlalchemy.orm import scoped_session, sessionmaker app = Flask(__name__) # Configure session to use filesystem app.config["SESSION_PERMANENT"] = False app.config["SESSION_TYPE"] = "filesystem" # Session(app) # Set up database engine = create_engine(os.getenv("DATABASE_URL")) db = scoped_session(sessionmaker(bind=engine)) print (os.getenv("DATABASE_URL")) def main(): f = open("books.csv") reader = csv.reader(f) for isbn, title, author, year in reader: if db.execute("SELECT * FROM authors WHERE name = :author", {"name": author}).rowcount == 0: db.execute("INSERT INTO authors (name) VALUES (author)") print(f" {author} was read.") db.commit() if __name__ == "__main__": main() ==================================================================== If I comment out the "if" statement then the authors all print on screen. But when I run this with the if statement I am getting a message that says: ssqlalchemy.exc.StatementError: (sqlalchemy.exc.InvalidRequestError) A value is required for bind parameter 'author' [SQL: SELECT * FROM authors WHERE name = %(author)s] [parameters: [{'name': 'author'}]] What am I missing? Al (Buddy) Peacock, PMP, MCCT, ITILv3, SMC, CSM, SPOC (920) 740-3411 linkedin.com/in/buddypeacock <https://www.linkedin.com/in/buddypeacock/>

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Re: Behaviour of os.path.join
by BlindAnagram May 28, 2020

May 28, 2020

On 27/05/2020 23:39, Roel Schroeven wrote: > BlindAnagram schreef op 27/05/2020 om 22:55: >> On 27/05/2020 18:42, Roel Schroeven wrote: >>> BlindAnagram schreef op 27/05/2020 om 18:53: >>>> Its not my bug to fix - the semantics of what I send is very clear on >>>> any Windows system. >>> >>> That's the first time I see any mention of those semantics, and I've >>> been using Windows since the Windows 3.1 days (and MS-DOS before that, >>> since 3.2 IIRC). >> >> Well I can only say that I am surpised that anyone working on Windows >> code development for as long as you have doesn't know that a path that >> ends in '\\' is a path to a directory. > > A path ending in a backslash cannot refer to a file, that much is true. > So if you have such a path and you insist that path is not an incomplete > path, than it must out of necessity be a directory. But a path not > ending in a backslash can refer to a directory just as well. I understand that directory paths do not necessarily end in a '\\'. But I am NOT claiming that paths on Windows are paths to directories if and only if they end in '\\' - there is only ONE 'if' in my claim. And this can be refuted with a single counterexample. > If those semantics are as clear as you say, it shouldn't be too > difficult to point us to a section in the Windows documentation that > confirms that. I don't know whether, in the many gigabytes of MS documentation that exists since Windows first emerged, this has ever been explicitly stated. And I am not going to look as it isn't important to me that people accept my claim. But I do find it interesting that it seems important to others here that I should withdraw it. [snip] > I find no hints of adding a backslash at the end to indicate directories. > If you can point me to convincing evidence in the documentation I'll > change my mind. And if you find a counterexample, I will change mine. > I'm sorry if my language seems abrasive; that is not my intention. I'm > only trying to help you and clear up a misunderstanding (which could be > mine, if it turns out you're right after all). No need to apologise, I don't have any problem with your input to this exchange.

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Re: Behaviour of os.path.join
by BlindAnagram May 28, 2020

May 28, 2020

On 27/05/2020 18:42, Roel Schroeven wrote: > BlindAnagram schreef op 27/05/2020 om 18:53: >> Its not my bug to fix - the semantics of what I send is very clear on >> any Windows system. > > That's the first time I see any mention of those semantics, and I've > been using Windows since the Windows 3.1 days (and MS-DOS before that, > since 3.2 IIRC). Well I can only say that I am surpised that anyone working on Windows code development for as long as you have doesn't know that a path that ends in '\\' is a path to a directory.

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Re: Behaviour of os.path.join
by BlindAnagram May 28, 2020

May 28, 2020

On 27/05/2020 23:39, Roel Schroeven wrote: > I find no hints of adding a backslash at the end to indicate directories. > > If you can point me to convincing evidence in the documentation I'll > change my mind. See the post from Eryk Sun, later in this thread.

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Re: Behaviour of os.path.join
by BlindAnagram May 28, 2020

May 28, 2020

On 28/05/2020 14:51, Eryk Sun wrote: > On 5/27/20, Chris Angelico <rosuav(a)gmail.com> wrote: >> On Thu, May 28, 2020 at 7:07 AM BlindAnagram <blindanagram(a)nowhere.com> >> wrote: >>> You can define a path however you want but it won't change the fact that >>> on Windows a path that ends in '\\' is inherently a path to a directory. >> >> Citation needed. > > See [MS-FSA] 2.1.5.1 Server Requests an Open of a File [1]. Here are > the relevant statements: > > The operation MUST be failed with STATUS_OBJECT_NAME_INVALID under > any of the following conditions: > .... > * If PathName contains a trailing backslash and > CreateOptions.FILE_NON_DIRECTORY_FILE is TRUE. > > .... > If PathName contains a trailing backslash: > * If StreamTypeToOpen is DataStream or > CreateOptions.FILE_NON_DIRECTORY_FILE is TRUE, the operation MUST > be failed with STATUS_OBJECT_NAME_INVALID > > Internally, WinAPI CreateFileW calls NTAPI NtCreateFile with the > create option FILE_NON_DIRECTORY_FILE (i.e. only open or create a data > file stream), unless backup semantics are requested in order to be > able to open a directory (i.e. an index stream), in which case the > call uses neither FILE_NON_DIRECTORY_FILE nor FILE_DIRECTORY_FILE and > leaves it up to the path name. In other words, with backup semantics, > if you need to ensure that only a directory is opened, add a trailing > slash. > > NTAPI STATUS_OBJECT_NAME_INVALID translates to WinAPI > ERROR_INVALID_NAME (123), which translates to C EINVAL (22). > > [1]: https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-fsa/8ada5fb… > Thank you for making the effort to answer a number of issues raaised in this thread. I much appreciate your input.

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Elegant hack or gross hack? TextWrapper and escape codes
by Chris Angelico May 28, 2020

May 28, 2020

Situation: A terminal application. Requirement: Display nicely-wrapped text. With colour codes in it. And that text might be indented to any depth. label = f"{indent}\U0010cc32{code}\U0010cc00 @{tweet['user']['screen_name']}: " wrapper = textwrap.TextWrapper( initial_indent=label, subsequent_indent=indent + " " * 12, width=shutil.get_terminal_size().columns, break_long_words=False, break_on_hyphens=False, # Stop URLs from breaking ) for line in tweet["full_text"].splitlines(): print(wrapper.fill(line) .replace("\U0010cc32", "\x1b[32m\u2026") .replace("\U0010cc00", "\u2026\x1b[0m") ) wrapper.initial_indent = wrapper.subsequent_indent # For subsequent lines, just indent them The parameter "indent" is always some number of spaces (possibly zero). If I simply include the escape codes in the label, their characters will be counted, and the first line will be shorter. Rather than mess with how textwrap defines text, I just replace the escape codes *and one other character* with a placeholder. In the final display, \U0010cc32 means "colour code 32 and an ellipsis", and \U0010cc00 means "colour code 0 and an ellipsis", so textwrap correctly counts them as one character each. So what do you folks think? Is this a gloriously elegant way to collapse nonprinting text, or is it a gross hacky mess that's going to cause problems? ChrisA

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Re: Custom logging function
by zljubisic＠gmail.com May 28, 2020

May 28, 2020

> You create two stream handlers that both log to stderr -- one with > basicConfig() and one explicitly in your code. That's probably not what you > want. How can I just add terminator = '\r\n' to the code bellow? Where should I put it? import logging LOG_LEVEL = logging.getLevelName('DEBUG') logging.basicConfig(level=LOG_LEVEL, format='%(asctime)s %(levelname)s %(name)s %(funcName)-20s %(message)s', datefmt='%d.%m.%Y %H:%M:%S') logging.info('Main script started')

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Access an object to which being bound
by Abdur-Rahmaan Janhangeer May 27, 2020

May 27, 2020

Greetings, Lets say i have class A: ... class B: self.x = A then used b = B() z = b.x() now how in A i get a reference to B when z is assigned to b.x? Thanks Kind Regards, Abdur-Rahmaan Janhangeer compileralchemy <https://compileralchemy.github.io/> | blog <https://abdur-rahmaanj.github.io/> github <https://github.com/Abdur-RahmaanJ> Mauritius

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