Python Programming

One of my recent research tasks required me to retrieve various information from del.icio.us, a well-known social bookmarking service. My programming language of choice is Python, and so I wrote a basic Python module for getting the data I needed.

Last week we looked at the itertools module and how its iterator based functions can be faster than doing things from scratch. One of the examples showed a function using itertools.takewhile to be much faster than one using itertools.groupby. Some feedback we got, asked, what then is the point of groupby if it's just a slower version of other functionality?

Louie provides Python programmers with a straightforward way to dispatch signals between objects in a wide variety of contexts. It is based on PyDispatcher, which in turn was based on a highly-rated recipe in the Python Cookbook. Louie is licensed under The BSD License.

### def reverse(l): return reduce(lambda x, y: [y] + x, [[]] + l) ###

Charming Python: SimPy simplifies complex models

 > According to the fact that all Thread run on the same CPU (if i didn't  > understand wrong), i'm asking if python will suffer from the future  > multicore CPU. Will not python use only one core, then a half or a  > quarter of CPU ? It could be a serious problem for the future of python... I agree that it could potentially be a serious hindrance for cpython if "multiple core" CPUs become commonplace. This is in contrast to jython and ironpython, both of which support multiple-cpu parallelism. Although I completely accept the usual arguments offered in defense of the GIL, i.e. that it isn't a problem in the great majority of use cases, I think that position will become more difficult to defend as desktop CPUs sprout more and more execution pipelines. I think that this also fits in with AM Kuchling's recent musing/thesis/prediction that the existing cpython VM may no longer be in use in 5 years, and that it may be superceded by python "interpreters" running on top of other VMs, namely the JVM, the CLR, Smalltalk VM, Parrot, etc, etc, etc. http://www.amk.ca/diary/archives/cat_python.html#003382 I too agree with Andrew's basic position: the Python language needs a period of library consolidation. There is so much duplication of functionality out there, with the situation only getting worse as people re-invent the wheel yet again using newer features such generators, gen-exps and decorators.

PyScripter is a free and open-source Python Integrated Development Environment (IDE) created with the ambition to become competitive in functionality with commercial Windows-based IDEs available for other languages. Being built in a compiled language is rather snappier than some of the other Python IDEs and provides an extensive blend of features that make it a productive Python development environment. 

interpreter:>>>import matplotlib>>>matplotlib.interactive(True)>>>matplotlib.use("WXAgg")>>>from matplotlib.pylab import *>>>plot([1,2,3])>>>xlabel('time (s)') 

PyScripter is a free and open-source Python Integrated Development Environment (IDE) created with the ambition to become competitive in functionality with commercial Windows-based IDEs available for other languages. Being built in a compiled language is rather snappier than some of the other Python IDEs and provides an extensive blend of features that make it a productive Python development environment.

in PyCrypto: >>> key = os.urandom(16) # Generate 16 random bytes (128 bits) >>> bin_to_hex(key) # Show the key in hex (32 characters) '61aa60e43a5e7fdb4b86a4897b52a0dc' >>> y = RFC1751.key_to_english(key) >>> y # Show the pass phrase version of the key 'BUSY BARN RUB DOLE TAUT TOOK ALTO PRY KIT WALL MUG CURT' >>> # The transformation is always reversible >>> bin_to_hex(RFC1751.english_to_key(y)) '61aa60e43a5e7fdb4b86a4897b52a0dc'

Human-Readable Encryption Keys

This is something I always forget how to do, and it's kind of hard to Google or search the Python docs because you can't search for **.The point is, when using **kwargs, you have to use the ** prefix not only in the function definition, but also in the call, prefixed to the variable you want to use as a keyword dictionary.

There are two applications that require using the NumPy array type in C extension modules: Access to numerical libraries: Extension modules can be used to make numerical libraries written in C (or languages linkable to C, such as Fortran) accessible to Python programs. The NumPy array type has the advantage of using the same data layout as arrays in C and Fortran. Mixed-language numerical code: In most numerical applications, only a small part of the total code is CPU time intensive. Only this part should thus be written in C, the rest can be written in Python. NumPy arrays are important for the interface between these two parts, because they provide equally simple access to their contents from Python and from C. This document is a tutorial for using NumPy arrays in C extensions.

> Is there a way to find the number of processors on a machine (on linux/ > windows/macos/cygwin) using python code (using the same code/cross > platform code)? From processing <http://cheeseshop.python.org/pypi/processing/0.34> : def cpuCount():     '''     Returns the number of CPUs in the system     '''     if sys.platform == 'win32':         try:             num = int(os.environ['NUMBER_OF_PROCESSORS'])         except (ValueError, KeyError):             pass     elif sys.platform == 'darwin':         try:             num = int(os.popen('sysctl -n hw.ncpu').read())         except ValueError:             pass     else:         try:             num = os.sysconf('SC_NPROCESSORS_ONLN')         except (ValueError, OSError, AttributeError):             pass     if num >= 1:         return num     else:         raise NotImplementedError --

SendKeys SendKeys(keys, pause = 0.05, with_spaces = False, with_tabs = False, with_newlines = False, turn_off_numlock = True) Parameters keys : str A string of keys. pause : float The number of seconds to wait between sending each key or key combination. with_spaces : bool Whether to treat spaces as {SPACE}. If False, spaces are ignored. with_tabs : bool Whether to treat tabs as {TAB}. If False, tabs are ignored. with_newlines : bool Whether to treat newlines as {ENTER}. If False, newlines are ignored. turn_off_numlock : bool Whether to turn off NUMLOCK before sending keys.

Key Code BACKSPACE {BACKSPACE}, {BS}, or {BKSP} BREAK {BREAK} CAPS LOCK {CAPSLOCK} or {CAP} DEL or DELETE {DELETE} or {DEL} DOWN ARROW {DOWN} END {END} ENTER {ENTER} or ~ ESC {ESC} HELP {HELP} HOME {HOME} INS or INSERT {INSERT} or {INS} LEFT ARROW {LEFT} NUM LOCK {NUMLOCK} PAGE DOWN {PGDN} PAGE UP {PGUP} PRINT SCREEN {PRTSC} RIGHT ARROW {RIGHT} SCROLL LOCK {SCROLLLOCK} SPACE BAR {PACE} TAB {TAB} UP ARROW {UP} F1 {F1} F2 {F2} F3 {F3} F4 {F4} F5 {F5} F6 {F6} F7 {F7} F8 {F8} F9 {F9} F10 {F10} F11 {F11} F12 {F12} F13 {F13} F14 {F14} F15 {F15} F16 {F16} F17 {F17} F18 {F18} F19 {F19} F20 {F20} F21 {F21} F22 {F22} F23 {F23} F24 {F24} Keypad add {ADD} Keypad subtract {SUBTRACT} Keypad multiply {MULTIPLY} Keypad divide {DIVIDE} Left Windows(R) {LWIN} Right Windows(R) {RWIN}

Use a staticmethod when you know which class you want to access as you are writing the code.

Use a classmethod if you have a class hierarchy and want the method to operate on the actual class used in the call rather than the class where it was defined:

Charming Python: Using state machinesAlgorithms and programming approaches in Python

my Python threads programming tutorial

You can use Microsoft Script Control. If you have the win32 extensions of python, you can use python in place of vb in this control -open the VBA script editor - In menus/Tools/References add Microsoft Script Control -Make a new module and declare a new MsScriptControl.ScriptControl Global sc as new MsScriptControl.ScriptControl -Initialize the language attibute with python - Note that you and users of your document must have python and its win32 extensions installed. Activestate python distribustion include it. You can put sc.language="python" in the routine Workbook_Open() Now you can import python modules using ExecuteStatement method of the control in vba and have results from python functions with eval method. One interesting thing is that you can pass an object to the control with AddObject method and have python manipulate it. And so on..

Global sc As New MSScriptControl.ScriptControl Public Function os_getcwd() sc.Language = "python" sc.ExecuteStatement ("import os") os_getcwd = sc.Eval("os.getcwd()") End Function With this you can set your Excel formula to =os_getcwd() For me it returns "C:\Documents and Settings\Administrator\My Documents", which I needed to know at the time so I didn't have to screw around with the ever annoying pythonpath. You can put the first two lines of the function in the Workbook_Open hook, but I don't know where that is. I hope to use more Python in Excel soon. Hmm, actually, I suppose you can put those first two lines of the function after the Global declaration as well. I know just about zero VBScript and didn't get a chance to do anything else beyond proof of concept yet. I figured I would write something dynamic which allowed more transparent access to Python, maybe allowing formula like =py("os.getcwd()"), etc.