🌐 Mailman 3 June 2009 - Python-list - python.org

"where" in python
by Chris June 4, 2009

June 4, 2009

I am a newby in Python and I'm first looking for equivalent to things I already manage: IDL. For example, I want to plot a sub-set of points, selected from a bigger set by applying some filter. In my example, I want to select only the values > 0. I succeed to write 5 different ways to do this, which one is the more efficient, the quicker, the more Python? It seems the 4th method give wrong results, but I don't know why... Thanks for your tips, Christophe ------------------------------------------------------------------------------------------ import pylab as pylab import numpy as numpy #Read the data d=pylab.load('Tabla_General2.cvs',comments='#',delimiter=';') # Define the columns to plot i_x = 10 i_y = 5 # Select the points to plot, 1rst method b_where = (d[:,i_x]>0) & (d[:,i_y]>0) xb = d[b_where,i_x] yb = d[b_where,i_y] # 2nd method xb2=pylab.compress(b_where,d[:,i_x]) yb2=pylab.compress(b_where,d[:,i_y]) # 3rd method i_where = pylab.where((d[:,i_x]>0) & (d[:,i_y]>0),1,0) xi = d[i_where,i_x] yi = d[i_where,i_y] # 4th method xi2=pylab.compress(i_where,d[:,i_x]) yi2=pylab.compress(i_where,d[:,i_y]) #5th method in_where = numpy.transpose(numpy.where((d[:,i_x]>0) & (d[:,i_y]>0))) xin = d[in_where,i_x] yin = d[in_where,i_y] ------------------------------------------------------------------------------

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Re: Using C++ and ctypes together: a vast conspiracy? ;)
by Thomas Heller June 4, 2009

June 4, 2009

[Please keep the discussion on the list] Joseph Garvin schrieb: > On Thu, Jun 4, 2009 at 3:43 AM, Thomas Heller <theller(a)python.net> wrote: >> There have been some attempts to use ctypes to access C++ objects. >> We (Roman Yakovenko and myself) made some progress. We were able to >> handle C++ name mangling, the special C++ calling convention, >> access virtual, non-virtual, overloaded functions, but finally gave up >> because the binary layout (function tables, member variables, and so on) >> of C++ objects is way too complicated and undocumented. > > Have you read the book Inside The C++ Object Model?: I haven't, but considered to buy it ;-) > http://www.amazon.com/Inside-Object-Model-Stanley-Lippman/dp/0201834545/ref… > > It's probably out of date now, but I'm about halfway through it and it > documents a ton of the little unexpected optimizations and such that > cause the binary layout to be complex. How did you get as far as you > did without having figured out the layout? (e.g. if you could access > virtual functions you must have known how to get at the virtual table) I found a lot of material on the web, also I used the (very good) visual studio debugger, and finally I did a lot of experimentation. We were only able to access some very simple C++ objects. There is also a patent or patents from MS about the vtable. All in all, as I said, IMO it is too complicated to figure out the binary layout of the C++ objects (without using a C++ compiler), also there are quite some Python packages for accessing them. -- Thanks, Thomas

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Re: Using C++ and ctypes together: a vast conspiracy? ;)
by Thomas Heller June 4, 2009

June 4, 2009

Philip Semanchuk schrieb: > Hi Thomas, > We're weighing options for accessing C++ objects via Python. I know of > SIWG and Boost; are there others that you think deserve consideration? I haven't used any of them myself. A common suggestion is SIP, less known are pybindgen and Robin. But there may be many more, and others with more experience might have much more to say about them. Also there is Roman Yokavenko's pygccxml which has a lot of stuff. > I've been happy with ctypes in my limited exposure to it and would > love to find a way to make that work. This thread has been very > interesting to me. Unfortunately there is no solution in sight, with ctypes.

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MultiReplace (performance and unordered dicts)
by Joseph Reagle June 4, 2009

June 4, 2009

I have programs that do lots of string-to-string replacements, so I'm trying to create a speedy implementation (tons of .replace statements has become unwieldy). My MultiReplace object does as well as the function regexp, which both do better than the for loop function, any other suggestions? def multi_repl(text, subs): for ori, sub in subs: text = text.replace(ori, sub) return text import string latex_esc_dic = dict(latex_esc) latex_esc_ori, latex_esc_rep = zip(*latex_esc) def symbol_replace(match, get=latex_esc_dic.get): return get(match.group(1), "") symbol_pattern = re.compile( "(" + string.join(map(re.escape, latex_esc_ori), "|") + ")" ) class MultiReplace(object): """ Replace multiple instances from a list of ori/rep pairs. I use an object for performance: compiled regexes persist. Table is a list of pairs, I have to convert to dict for regex replace function, don't use a dict natively since they aren't ordered. """ def __init__(self, table): print "initing object" self.originals, self.replacements = zip(*table) self.pattern = re.compile( "(" + string.join(map(re.escape, self.originals), "|") + ")" ) self.table_dic = dict(table) def _get_replacement(self, match): # passed match #print "replacing %s with %s" % (match.group(1), self.table_dic.get(match.group(1), "")) return self.table_dic.get(match.group(1), "") # use match to return replacement def replace(self, line): return self.pattern.sub(self._get_replacement, line) # pass replacement function mr = MultiReplace(latex_esc) ... #line = multi_repl(line, latex_esc) # 0.406 #line = symbol_pattern.sub(symbol_replace, line) #0.385 line = mr.replace(line) #0.385

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Illegal seek with os.popen
by pruebauno＠latinmail.com June 4, 2009

June 4, 2009

Should I open a bug report for this? Python 2.5.1 (r251:54863, Sep 19 2007, 14:58:06) [C] on aix5 Type "help", "copyright", "credits" or "license" for more information. >>> import os >>> os.popen('cat','w') <open file 'cat', mode 'w' at 0x110111990> >>> Python 3.1rc1 (r31rc1:73054, Jun 1 2009, 10:49:24) [C] on aix5 Type "help", "copyright", "credits" or "license" for more information. >>> os.popen('cat','w') Traceback (most recent call last): File "<stdin>", line 1, in <module> File "/Python-3.1rc1/Lib/os.py", line 641, in popen return _wrap_close(io.TextIOWrapper(proc.stdin), proc) IOError: [Errno 29] Illegal seek >>>

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Re: import sqlite3
by willgun June 4, 2009

June 4, 2009

Andrew McNamara 写道: > > On 04/06/2009, at 3:15 PM, willgun wrote: >> >> When i run the following in IDLE: >> IDLE 2.6.1 >>>>> import sqlite3 >>>>> con =sqlite3.connect (r'g:\db1') >>>>> >> everything goes well,but when i save these to a .py file and run it: >> >>>>> >> Traceback (most recent call last): >> File "C:\Users\hp\Desktop\SQLite3\sqlite3.py", line 2, in <module> >> import sqlite3 >> File "C:\Users\hp\Desktop\SQLite3\sqlite3.py", line 3, in <module> >> con=sqlite3.connect(r'g:\db1') >> AttributeError: 'module' object has no attribute 'connect' >> >> Anyone can tell me why? > > What did you call the .py file? sqlite3.py? If so, you've just imported > your own module again. 8-) > > After the import, try "print sqlite3.__file__", which will tell you > where the module came from. Thank you all the same. I'm a student from China.It's painful for us to read python documentation entirely due to poor english.So I often make these mistakes.

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Is socket.shutdown(1) useless
by Mohamed Garrana June 4, 2009

June 4, 2009

Hello This is is in answer for Is socket.shutdown(1) useless Shutdown(1) , forces the socket no to send any more data This is usefull in Buffer flushing Strange error detection Safe guarding Let me explain more , when you send a data , it's not guaranteed to be sent to your peer , it's only guaranteed to be sent to the os buffer , which in turn sends it to the peer os buffer So by doing shutdown(1) , you flush your buffer and an error is raised if the buffer is not empty ie: data has not been sent to the peer yet Howoever this is irrevesable , so you can do that after you completely sent all your data and you want to be sure that it's atleast at the peer os buffer Everything's ok in the end...if it's not ok, then its not the end. P save paper...

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DUDA !!!!!!!!!!
by Ariel Vazquez Riveron June 4, 2009

June 4, 2009

Hola: Hoy en día me encuentro iniciandome dentro del python, en estos momentos quiero saber de que forma puedo eliminar un archivo de un compactado, ya sea zip, rar o cualquier otro. Estudie las librerías zipfile pero no tiene ninguna funcion que me permita hacerlo. Trabajo con python 2.5 salu2 Ariel ---------------------------------------------------------------- This message was sent using IMP, the Internet Messaging Program.

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Re: Get the hard disk hardware serial number
by Nick Craig-Wood June 4, 2009

June 4, 2009

MRAB <python(a)mrabarnett.plus.com> wrote: > Jorge wrote: > > I need to know how to get the hardware serial number of a hard disk in > > python. > > > For Windows, see http://www.daniweb.com/forums/thread187326.html For linux I'd run this and parse the results. # smartctl -i /dev/sda smartctl version 5.38 [i686-pc-linux-gnu] Copyright (C) 2002-8 Bruce Allen Home page is http://smartmontools.sourceforge.net/ === START OF INFORMATION SECTION === Model Family: Seagate Momentus 7200.2 Device Model: ST9200420AS Serial Number: 7QW138AK Firmware Version: 3.AAA User Capacity: 200,049,647,616 bytes Device is: In smartctl database [for details use: -P show] ATA Version is: 7 ATA Standard is: Exact ATA specification draft version not indicated Local Time is: Thu Jun 4 09:30:23 2009 BST SMART support is: Available - device has SMART capability. SMART support is: Enabled According to the man page smartctl also runs under windows/mac/solaris etc -- Nick Craig-Wood <nick(a)craig-wood.com> -- http://www.craig-wood.com/nick

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Re: Get the hard disk hardware serial number
by Dietmar Schwertberger June 4, 2009

June 4, 2009

MRAB schrieb: > Jorge wrote: >> I need to know how to get the hardware serial number of a hard disk in >> python. >> > For Windows, see http://www.daniweb.com/forums/thread187326.html This recipe uses the function GetVolumeInformation(), which does not return the hardware serial number. From the microsoft documentation: This function returns the volume serial number that the operating system assigns when a hard disk is formatted. To programmatically obtain the hard disk's serial number that the manufacturer assigns, use the Windows Management Instrumentation (WMI) Win32_PhysicalMedia property SerialNumber. The WMI method is e.g. described here: http://www.velocityreviews.com/forums/t359670-wmi-help.html import wmi c = wmi.WMI() for pm in c.Win32_PhysicalMedia(): print pm.Tag, pm.SerialNumber or to retrieve the serial number for the installation drive: serial = c.Win32_PhysicalMedia(["SerialNumber"], Tag=r"\\.\PHYSICALDRIVE0")[0].SerialNumber.strip() Regards, Dietmar

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