I have been investigating jython a bit, and at the jython terminal accidentally typed 1 = 2 instead of q = 2, and found this:
>>> 1 = 2
...
...
I had to Ctrl+C to get out of it. No other input seems to make it happy.
I put the same code in a script and ran it with the same behavior (it just hangs).
In CPython, I get a SyntaxError: can't assign to literal (as expected).
Any idea what's going on? Is this just a jython bug?
$ jython
Jython 2.5.2 (Debian:hg/91332231a448, Jun 3 2012, 09:02:34)
[OpenJDK 64-Bit Server VM (Oracle Corporation)] on java1.7.0_51
Related
Querying DB2 from python using ODBC, I am seeing NULL values converted to 0 (on Linux, seemingly corrupt but close to 0 on Mac M1 -- even more worryingly).
This is using the db2 docker image started like this:
docker run -itd --name db2 --privileged=true -p 50000:50000 -e LICENSE=accept -e DB2INST1_PASSWORD=xxxxx -e DBNAME=testdb -v <db storage dir>:/database ibmcom/db2
Code as follows recreates the issue:
import pyodbc
cs = "Driver={ODBC Driver v11.5.7 for DB2};Database=xxxxx;Hostname=xxxx;Port=50000;Protocol=TCPIP;Uid=xxxx;Pwd=xxxx;"
cnxn = pyodbc.connect(cs)
crsr = cnxn.cursor()
crsr.execute("SELECT CAST(NULL AS INT), CAST(NULL AS REAL) FROM SYSIBM.SYSDUMMY1");
print(crsr.messages)
print(crsr.fetchall())
Outputs:
❯ python float-test.py
[]
[(2, 4.2439915814e-314)]
Is it expected that I can't retrieve NULL values as plain data types? It seems to be allowed in PostgreSQL. I know I can cast around this but would rather not, obviously.
Extra Info
It does seem that the ODBC driver version 11.5.7 from Fix Central suffers this issue whilst the 11.5.6 version from https://public.dhe.ibm.com/ibmdl/export/pub/software/data/db2/drivers/odbc_cli does not.
As mentioned in comments, it appears pyodbc is impacted and both plain ibm_db and DBI are not impacted (both return None, None). So at least there is a workaround.
The reason for the behaviour deifference is that pyodbc is using SQLGetData() while the other two use the SQLBindCol() methods of extracting the result set data.
IBM's clidriver on Linux x64, SQLGetData() sets the (SQLLEN *) StrLen_Or_IndPtr parameter to SQL_NULL_DATA when the value of the column in result-set is NULL. But the problem is that IBMs clidrver sets StrLen_or_IndPtr to SQL_NULL_DATA (as int, 4 bytes), when pyodbc code expects it to SQL_NULL_DATA (as SQLLEN, 8bytes on Linux x64) as SQLLEN is the documented datatype for the StrLen_or_IndPtr argument.
Therefore the comparison in pyodbc getdata.cpp GetDataDouble() :
if ( cbFetched == SQL_NULL_DATA )
Py_RETURN_NONE;
will be false, causing the code to return an unitialised variable instead of Py_None.
I do not know if the maintainers of pyodbc run their tests against a Db2-LUW product, but it looks like other parts of the code could suffer the same problem and other issues may lurk. Consider asking on github what is the support policy for Db2-LUW in pyodbc.
If you have a support contract, IBM should also be asked to comment on their reason for not respecting the datatype of StrLen_Or_IndPtr when writing SQL_NULL_DATA to this parameter on Linux x64.
This Python code shows how to call some process in Windows 10 and to send to it string commands, to read its string responses through stdin, stdout pipes of the process:
Python 3.8.0 (tags/v3.8.0:fa919fd, Oct 14 2019, 19:37:50) [MSC v.1916 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> from subprocess import *
>>> p = Popen("c:/python38/python.exe", stdin=PIPE, stdout=PIPE)
>>> p.stdin.write(b"print(1+9)\n")
11
>>> p.communicate()
(b'10\r\n', None)
>>>
As you can see the python.exe process returned 10 as an answer to print(1+9). Now I want to do the same in Pharo (or Squeak): in Windows 10 OS - I suppose something similar, i.e. short, simple, understandable, really working.
I installed OSProcess, ProcessWrapper (they were missing in Pharo, also its strange that I got warning that they are not marked for Pharo 8.0 and were not checked to work in Pharo 8.0, but OK), and I tried ProcessWrapper, PipeableOSProcess (copy-pasted different snippets from the Web), etc - with zero success! The results were:
nothing happens, python.exe was not started
VM errors console was opened (white console in the bottom of the Pharo, which is controlled with F2 menu)
different exceptions
etc
Would somebody show me simple working example how to start a process and to to send it commands, read answers, then send again, and so on in some loop - I plan to have such communication in a detached thread and to use it as some service, because Pharo, Smalltalk in general is missing most bindings, so then I will use subprocess communication like in "good" old days...
I know how to call a command and to get its output:
out := LibC resultOfCommand: 'dir ', aDir.
but I am talking about another scenario: a communication with a running process interactively (for example, with SSH or similar like in the example above - python.exe).
PS. Maybe it's possible to do it with LibC #pipe:mode even?
Let me start with that the PipeableOsProcess is probably broken on Windows. I have tried it and it just opened a command line and nothing else (it does not freeze my Pharo 8). The whole OSProcess does not work correctly in my eyes.
So I took a shot at LibC which is supposed to not work with Windows.
I’m a module defining access to standard LibC. I’m available under Linux and OSX, but not under Windows for obvious reasons :)
Next is to say that Python's Windows support is probably much better than Pharo's.
The solution, which is more like a workaround using files, is to use LibC and #runCommand: (I tried to come up with a similar example as you had shown above):
| count command result outputFile errorFile |
count := 9+1. "The counting"
command := 'echo ', count asString. "command run at the command line"
outputFile := 'output'. "a file into which the output is redirected"
errorFile := 'error'. "a file where the error output is redirected "
result := LibC runCommand: command, "run the command "
' >', outputFile, "redirect the output to output file"
' 2>', errorFile.
"reading back the value from output file"
outputFile asFileReference contents lines.
"reading back the value from the error file - which is empty in this case"
errorFile asFileReference contents lines.
I'm relatively inexperienced in coding, so right now I'm just familiarizing myself with the basics of how to use SE, which I'll need to use in the near future.
At the moment I'm trying to get it to analyze a FITS file on my computer (which is a Mac). I'm sure this is something obvious, but I haven't been able to get it do that. Following the instructions in Chapters 6 and 7 of Source Extractor for Dummies (linked below), I input the following:
sex MedSpiral_20deg_Serl2_.45_.fits.fits -c configuration_file.txt
And got the following error message:
WARNING: configuration_file.txt not found, using internal defaults
----- SExtractor 2.19.5 started on 2020-02-05 at 17:10:59 with 1 thread
Setting catalog parameters
ERROR: can't read default.param
I then tried entering parameters manually:
sex MedSpiral_20deg_Ser12_.45_.fits.fits -c configuration_file.txt -DETECT_TYPE CCD -MAG_ZEROPOINT 2.5 -PIXEL_SCALE 0 -SATUR_LEVEL 1 -SEEING_FWHM 1
And got the same error message. I tried referencing default.sex directly:
sex MedSpiral_20deg_Ser12_.45_.fits.fits -c default.sex
And got the same error message again, substituting "configuration_file.txt not found" with "default.sex not found" (I checked that default.sex was on my computer, it is). The same thing happened when I tried to use default.param.
Here's the link to SE for Dummies (Chapter 6 begins on page 19):
http://astroa.physics.metu.edu.tr/MANUALS/sextractor/Guide2source_extractor.pdf
If you run the command "sex MedSpiral_20deg_Ser12_.45_fits.fits -c default.sex" within the config folder (within the sextractor folder), you will be able to run it.
However, I wonder how I can possibly run sextractor command from any folder in my computer?
I'm trying to test the continuation facility in Pharo, with this code(in the playground):
| cont f |
f:=[
|i|
i:=0.
Continuation currentDo: [ :cc | cont:=cc ].
i:=i+1.
].
f value. "1"
cont. "a Continuation"
However, as soon as I call the continuation saved in cont(replacing cont. by cont value.), the image freezes immediately, and I have to press atl+. to gain back control.
VM version: VM: NBCoInterpreter NativeBoost-CogPlugin-GuillermoPolito.19 uuid: acc98e51-2fba-4841-a965-2975997bba66 May 15 2014 NBCogit NativeBoost-CogPlugin-GuillermoPolito.19 uuid: acc98e51-2fba-4841-a965-2975997bba66 May 15 2014 https://github.com/pharo-project/pharo-vm.git Commit: ed4a4f59208968a21d82fd2406f75c2c4de558b2 Date: 2014-05-15 18:23:04 +0200 By: Esteban Lorenzano <estebanlm#gmail.com> Jenkins build #14826
Pharo version: [version] 4.0 #40614
Thanks.
Edit: I was stupid, didn't think this through...
You've effectively created an infinite loop by reevaluating the same code again and again. You can see that if you debug the code and step through it. The original context will always be restored and then evaluated starting with the first expression following the #currentDo: send. This is exactly what the continuation is supposed to do: save the current position in the execution and restart there later on.
I do not have a Fedora to test, however I tried your code in Ubuntu, using this version of Pharo:
wget -O- get.pharo.org/40+vm | bash
./pharo-ui Pharo.image
and your code seems to work properly :(
In case this error persists, could you be more specific about the version of the vm you are using?:
./pharo Pharo.image --version
And the version of Pharo you are using?:
./pharo Pharo.image printVersion
Also, send us the crash.dmp file would help a lot.
Why am I getting output on my console when writing to file? I don't recall this ever happening before...
outfile= open("C:\\Data\\testout.txt", 'w')
outfile.write("something")
outfile.write("something else")
output:
9
14
In Python versions > 3.0, the write method returns the number of bytes written.
http://docs.python.org/3/tutorial/inputoutput.html#methods-of-file-objects