🌐 Mailman 3 December 2008 - Python-list - python.org

Proposal: Decimal literals in Python.
by Lennart Benschop July 14, 2009

July 14, 2009

Python has had the Decimal data type for some time now. The Decimal data type is ideal for financial calculations. Using this data type would be more intuitive to computer novices than float as its rounding behaviour matches more closely what humans expect. More to the point: 0.1 and 0.01 are exact in Decimal and not exact in float. Unfortunately it is not very easy to access the Decimal data type. To obtain the decimal number 12.34 one has to do something like this: import decimal x=decimal.Decimal("12.34") Of course we can intruduce a single character function name as an alias for the Decimal type constructor, but even then we have to use both parentheses and quotes for each and every decimal constant. We cannot make it shorter than D("12.34") With Python 3000 major changes to the language are carried out anyway. My proposal would require relatively minor changes. My proposal: - Any decimal constant suffixed with the letter "D" or "d" will be interpreted as a literal of the Decimal type. This also goes for decimal constants with exponential notation. Examples of decimal literals: 1d 12.34d 1e-3d (equivalent to 0.001d) 1e3d (same value as 1000d, but without trailing zeros). 1.25e5d (same value as 125000d but without trailing zeros). When we print a decimal number or convert it to a string with str(), a trailing d should not be added. The repr function does yield strings with a trailing d. When decimal numbers are converted from strings, both numbers with and without a trailing d should be accepted. If we have decimal literals in the core language, we should probably have a type constructor in the core namespace, e.g. dec() along with int() and float(). We then need the decimal module only for the more advanced stuff like setcontext. Pros: - the Decimal data type will be more readily accessible, especially for novices. - Traling characters at the end of a literal are already used (the L for long). - It does not conflict with the syntax of other numeric constants or language constructs. - It does not change the meaning of existing valid literal constants. Constants that used to be float will continue to do so. Cons: - The lexical scanner of the Python interpreter will be slightly more complex. - The d suffix for constants with exponential notation is ugly. - Decimal numbers with exponentail notation like 2e5d could be mistaken for hex (by humans, not by the parser as hex requires the 0x prefix). - It requires the decimal module to be part of the core Python interpreter. -- Lennart

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Re: renice
by Dan July 14, 2009

July 14, 2009

On Oct 26, 4:30 am, mokhtar <mbmessa...(a)yahoo.com> wrote: > Hi > > Is it possible to renice the python process executing the current python > script ?:confused: > -- > View this message in context:http://www.nabble.com/renice-tf4695834.html#a13422771 > Sent from the Python - python-list mailing list archive at Nabble.com. On UNIX: >>> import os >>> os.system("renice -n %d %d" % ( new_nice, os.getpid() ) ) (untested) I don't know if windows has the concept of renice... -Dan

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Re: SSH utility
by Sean DiZazzo July 8, 2009

July 8, 2009

On Aug 11, 5:17 am, Edwin.Mad...(a)VerizonWireless.com wrote: > for similar tasks, I use pexpecthttp://pypi.python.org/pypi/pexpect. > > spawning bash process and simulate an interactive session. Here sending ls command, retrieving results and exiting. In the spawned process ssh or any other command, is just another command. > > ------------actual session-------------------------- > $ python > Python 2.5.1 (r251:54863, May 18 2007, 16:56:43) > [GCC 3.4.4 (cygming special, gdc 0.12, using dmd 0.125)] on cygwin > Type "help", "copyright", "credits" or "license" for more information.>>> import pexpect > >>> c = pexpect.spawn('/bin/bash') > >>> c.expect([pexpect.TIMEOUT, pexpect.EOF, '\$ ']) > 2 > >>> c.before, c.after > > ('\x1b[?1034hmadared@NJWARHQD0IT696A:~\r\n', '$ ')>>> c.sendline('ls') > 3 > >>> c.expect([pexpect.TIMEOUT, pexpect.EOF, '\$ ']) > 2 > >>> c.before, c.after > > ('ls\r\x.txt xx.txt xy.txt y.txt\r\nmadared@NJWARHQD0IT696A:~\r\n', '$ ')>>> c.sendline('exit') > 5 > >>> c.expect([pexpect.TIMEOUT, pexpect.EOF, '\$ ']) > 1 > >>> c.before, c.after > > ('exit\r\nexit\r\n', <class 'pexpect.EOF'>)>>> exit() > > madared@NJWARHQD0IT696A:~ > $ > --------------------------------------------------------------- > > hope that helps. > > regards. > Edwin > > -----Original Message----- > From: python-list-bounces+edwin.madari=verizonwireless....(a)python.org > > [mailto:python-list-bounces+edwin.madari=verizonwireless....@python.org] > On Behalf Of James Brady > Sent: Monday, August 11, 2008 12:26 AM > To: python-l...(a)python.org > Subject: SSH utility > > Hi all, > I'm looking for a python library that lets me execute shell commands > on remote machines. > > I've tried a few SSH utilities so far: paramiko, PySSH and pssh; > unfortunately all been unreliable, and repeated questions on their > respective mailing lists haven't been answered... > > It seems like the sort of commodity task that there should be a pretty > robust library for. Are there any suggestions for alternative > libraries or approaches? > > Thanks! > James > --http://mail.python.org/mailman/listinfo/python-list > > The information contained in this message and any attachment may be > proprietary, confidential, and privileged or subject to the work > product doctrine and thus protected from disclosure. If the reader > of this message is not the intended recipient, or an employee or > agent responsible for delivering this message to the intended > recipient, you are hereby notified that any dissemination, > distribution or copying of this communication is strictly prohibited. > If you have received this communication in error, please notify me > immediately by replying to this message and deleting it and all > copies and backups thereof. Thank you. I second pexpect and the nice little module that comes with it ssh_session.py. Been using it for ages now! ~Sean

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encoding problem
by digisatori＠gmail.com June 28, 2009

June 28, 2009

The below snippet code generates UnicodeDecodeError. #!/usr/bin/env python #--*-- coding: utf-8 --*-- s = 'äöü' u = unicode(s) It seems that the system use the default encoding- ASCII to decode the utf8 encoded string literal, and thus generates the error. The question is why the Python interpreter use the default encoding instead of "utf-8", which I explicitly declared in the source.

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Re: Iphone Going 3G!
by Shafiq May 6, 2009

May 6, 2009

apalah kau ni tak belajar ke bahasa menunjukkan bangsa "news.tm.net.my" <kutukutu(a)maha.com> wrote in message news:48df149c_1@news.tm.net.my... > relic wrote: >> fizzi wrote: >>> For the Iphone lovers out there, >> >> Wrong group. No weirdos here. > testtt

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Problems running on hp dual core processor
by jim-on-linux April 16, 2009

April 16, 2009

Python help, I have a number of clients running a program built with python 2.5. One has just purchased an HP with a duel core processor, 2.2G with .099g ram. On the new hp, when they try to print they get an import error; File win32ui.pyc line 12, in <module> File win32ui.pyc, line 10, in _load ImportError: DLL load failed: The specified module could not be found. The file is there The only difference I could find from their other machines is the processor.

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Unable to abort a FTP command?
by _wdx＠163.com April 15, 2009

April 15, 2009

Hi, I write the following script to retrieve a part of a large file from a FTP site: import ftplib class ftp_getter(object): def __init__(self): self.handle = ftplib.FTP('ftp_server_address') self.handle.set_debuglevel(2) self.login() def login(self): self.handle.login('user', 'pass') self.handle.cwd('/temp1/') def quit(self, is_close = False): self.handle.quit() if is_close: self.handle.close() print 'ftp handle closed' def getpart_callback(self, received): print "received a packet" if self.cnt <= 0: if not self.outf.closed: self.outf.close() if not self.aborted: try: self.handle.abort() self.aborted = True except Exception,ex: pass else: print 'received packet, [0] = %x' % ord(received[0]) self.outf.write(received) self.cnt -= len(received) def getpart(self, ftp_filename, rest, cnt, out_filename): self.outf = open(out_filename, 'wb') self.cnt = cnt self.aborted = False self.handle.retrbinary('RETR ' + ftp_filename, self.getpart_callback, 8192, rest) if not self.outf.closed: self.outf.close() if __name__ == '__main__': g = ftp_getter() g.getpart('FILE_TO_RETRIEVE.DAT', 50000, 20, 'out.dat') g.quit(True) print "all done." As the last four lines shown, I want to connect to my FTP server, retrieve 20 bytes starting at offset 50000 from FILE_TO_RETRIEVE.DAT, and stop retrieving after more than 20 bytes have been received. It's quite simple, but to my suprise, this code does not work. "self.handle.abort()" have been executed and I got the expected response from server(426), but the RETR command does not seem to stop at all. More and more data are received and getpart_callback method is called again and again. Why the RETR command is not actually aborted? Can anyone help me? Thanks Xu Wang

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Re: Problem Python 2.6.1 vs 2.6 & pyWin32
by "Martin v. Löwis" March 26, 2009

March 26, 2009

> Sorry for not being explicit. With "installer" I meant the binary > Windows installer you create with command "python setup.py > bdist_wininst". In the past we've been able to use > "package-version.win32.exe" files created with Python 2.5 on older > version, but that doesn't seem to be case with 2.6. I see. This has nothing to do with the OP's question, then. For Python 2.6, we switched to VS 2008. Apparently, the bdist_msi installers now get linked with the VS 2008 CRT (msvcr90.dll), which must be present on the system (in WinSxS) for the installer to run; one way of installing the CRT is to install Python for all users, another is to install it "just for me", and put \python26 into PATH (so that the installer can find msvcr90.dll). Regards, Martin

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Writing a well-behaved daemon
by Ben Finney March 25, 2009

March 25, 2009

Howdy all, Writing a Python program to become a Unix daemon is relatively well-documented: there's a recipe for detaching the process and running in its own process group. However, there's much more to a Unix daemon than simply detaching. At a minimum, a well-behaved Unix daemon must at least: * Detach the process into its own process group * Close stdin, redirect stdout and stderr to a null device * Handle its own PID file: refuse to start if the PID file already exists, write the PID file on startup otherwise, and remove the PID file on termination * Revoke setuid and setgid privileges, which are strongly deprecated these days * Handle interrupts, cleaning up the process and PID file as necessary * (possible others) There are also many other commonly-expected tasks that well-behaved Unix daemons perform (drop privileges to a nominated non-root user and group after daemonising, redirect output to syslog instead, operate in a chroot jail, respawn when terminated, etc.). All of this stuff has been done numerous times before, and the basics are mostly agreed upon. Yet all of these are tricky to implement correctly, and tedious to re-implement in every program intended to run as a daemon. The 'daemon' program <URL:http://www.libslack.org/daemon/> covers all these, and allows an arbitrary process to be started as a well-behaved Unix daemon process. It's not a good assumption that this program is installed on an arbitrary system though, and it seems excessive to ask the recipient of one's program to get a third-party program just in order to make a daemon process. I'd love to be able to have something similar for Python programs, e.g. a 'become_well_behaved_daemon()' function that implements all the above and perhaps takes optional arguments for the optional features. My searches for such functionality haven't borne much fruit though. Apart from scattered recipes, none of which cover all the essentials (let alone the optional features) of 'daemon', I can't find anything that could be relied upon. This is surprising, since I'd expect this in Python's standard library. Can anyone point me to the equivalent of the 'daemon' program in the form of a well-tested Python library? -- \ “Tis more blessed to give than to receive; for example, wedding | `\ presents.” —Henry L. Mencken | _o__) | Ben Finney

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decorators tutorials
by james_027 March 23, 2009

March 23, 2009

Hi, I am learning python by learning django, and I stumble upon decorator which is very cool, any beginners resources for python decorators, although I can google it, I just want to get a good tutorial for this topic. Thanks james

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