Popular recipes by Shao-chuan Wang

Windows directory walk using ctypes (Python)

2013-08-09T00:17:00-07:00

Python recipe 578629 by Shao-chuan Wang (ctypes, system).

Windows shell/explorer has a limit size of full path, but both NTFS and ReFS can support full path longer than the limit; this is making os.walk on Windows bad if files are in deeply nested folders, and therefore this recipe.

Converts doc files into text files on Windows platform (Python)

2012-05-08T06:39:43-07:00

Python recipe 578121 by Shao-chuan Wang (conversion, pythoncom, word).

READ BEFORE YOU USE THE CODE

Requirements

Windows platform
Python 2.7
pywin32, http://sourceforge.net/projects/pywin32/
Word application installed on running machine

Sync your facebook friends list to your address book on Mac/iPhone/iPad (Python)

2011-12-17T09:27:02-08:00

Python recipe 577986 by Shao-chuan Wang (address, book, facebook, sync).

READ BEFORE YOU USE THE CODE*

Requirement

Mac OS with python obj-c wrapper built-in. Typically, Mac OS Snow leopard, or Lion comes with python wrapper of objc.
If you want to also sync to your iphone, simply enable iCloud feature provided by apple, and run this script on a macbook with iCloud enabled.
Need fbconsole module, which can be downloaded at https://github.com/facebook/fbconsole

This script will download the profile pictures, first name, last name of your friends, and insert them into your address book if it does not exist.

Permutation and combination using recursive generator (Python)

2011-10-04T05:44:19-07:00

Python recipe 577890 by Shao-chuan Wang (combinatorics, generators, permutation, recursion). Revision 2.

This recipes demonstrates how to use recursive generator to implement permutation and combination.

Implementation of Knuth–Morris–Pratt algorithm (C)

2011-10-15T00:33:41-07:00

C recipe 577908 by Shao-chuan Wang (kmp, matching, string). Revision 2.

Knuth–Morris–Pratt (KMP) is a linear time string matching algorithm.

http://en.wikipedia.org/wiki/Knuth%E2%80%93Morris%E2%80%93Pratt_algorithm

This recipe gives a C-version implementation.

Dijkstra shortest path implementation (Python)

2011-10-05T09:06:50-07:00

Python recipe 577892 by Shao-chuan Wang (dijkstra, optimization, shortest).

This code snippet is the implementation of Dijkstra's algorithm.

Conversion of PIL Image and numpy array (Python)

2011-03-05T03:47:56-08:00

Python recipe 577591 by Shao-chuan Wang (numpy, pil). Revision 2.

The utility function that converts PIL image to numpy array and vice versa.

Calculation of total number of lines (Bash)

2011-05-23T10:55:45-07:00

Bash recipe 577717 by Shao-chuan Wang (line).

This bash script enables you to calculate the total number of lines of source code.

Example usage: 1. calculate total number of lines of java source files. $ line.sh java

calculate total number of lines of python source files. $ line.sh py

Bit operation (C)

2011-02-27T05:21:35-08:00

C recipe 577589 by Shao-chuan Wang (bit, operation).

A bit operation (could be very long).

Vectorize Operation (Python)

2011-02-05T05:36:19-08:00

Python recipe 577563 by Shao-chuan Wang (vector). Revision 2.

This python submodule enable you to do the vectorize calculation, such as vectorize add, and etc.

Command Threads (Python)

2010-12-25T23:23:49-08:00

Python recipe 577505 by Shao-chuan Wang (threading). Revision 4.

A thread that accepts callable objects as "commands" or "jobs" to execute.

A Profiling Tool (Python)

2011-03-04T05:41:04-08:00

Python recipe 577323 by Shao-chuan Wang (profiling, timing). Revision 2.

This is a decorator for doing the profiling of a function.

Minimum Cut Solver (Python)

2009-09-19T07:16:58-07:00

Python recipe 576907 by Shao-chuan Wang (algorithm, ford_fulkerson, mininum_cut, min_cut, stoer_wagner).

A Minimum Cut Solver

This python script is for solving the ACM problem Q2914: Minimum Cut. http://acm.pku.edu.cn/JudgeOnline/problem?id=2914

Instead of using Ford-Fulkerson method, I use Stoer and Wagner's Min cut Algorithm. http://www.cs.dartmouth.edu/~ac/Teach/CS105-Winter05/Handouts/stoerwagner-mincut.pdf

However I also include the max flow method (from wiki) for benchmark. The code can be found at: http://en.wikipedia.org/wiki/Ford-Fulkerson_algorithm

Shutdown your PC by using ctypes (Win32 Platform) (Python)

2009-08-03T10:05:38-07:00

Python recipe 576865 by Shao-chuan Wang (ctypes, reboot, shutdown, system_programming, win32).

It is true that by using win32 extension python modules, such as win32api, win32con, and win32security, we can easily shutdown the computer with a few steps. However, sometimes your python's runtime environment does not provide win32com module (because it is not a build-in module), we may have to shutdown the pc on our own.

By using ctypes, we are still able to shutdown or reboot the PC easily.

A Tree Finder (Python)

2009-09-26T09:36:58-07:00

Python recipe 576912 by Shao-chuan Wang (algorithm, tree).

This python script is for solving the ACM problem Q1308: Is It A Tree? http://acm.pku.edu.cn/JudgeOnline/problem?id=1308

Longest common subsequence problem solver (Python)

2009-08-06T06:36:56-07:00

Python recipe 576869 by Shao-chuan Wang (algorithm, decorator, lcs, longest_common_subsequence). Revision 2.

Longest common subsequence problem is a good example of dynamic programming, and also has its significance in biological applications.

For more information about LCS, please see: http://en.wikipedia.org/wiki/Longest_common_subsequence_problem

Also, here, I use a 'cached' decorator to keep core algorithm neat. You can see how great the decorator could be. :)

Also note that, this recipe is just a demonstration of LCS and the usage of a python decorator. However, the memory is not used very efficiently. If the problem is very large-scaled, it may lead to stack overflow or memory error.

So, do not use this recipe to deal with large-scaled problems. ;)

An unofficial interface of Yahoo's Chinese segmentation. (Python)

2009-07-27T21:59:20-07:00

Python recipe 576859 by Shao-chuan Wang (chinese, segmentation, yahoo).

An unofficial interface of Yahoo's Chinese segmentation.

Before use it, you MUST specify your APPID in the code. *

Yahoo's api documents: http://tw.developer.yahoo.com/cas/

Interval Execute a function (Python)

2009-04-24T08:58:27-07:00

Python recipe 576726 by Shao-chuan Wang (thread, timer). Revision 4.

Here I just want to keep it simple. If you want to execute a function every n second, this function should be competent. However, please note that the task is actually executed in another thread.

Huffman coding, Encoder/Deconder (Python)

2009-01-04T04:11:37-08:00

Python recipe 576603 by Shao-chuan Wang (algorithm, compression, decompression, huffman_code). Revision 2.

Please refer to wikipedia: http://en.wikipedia.org/wiki/Huffman_coding

Huffman coding is an entropy encoding algorithm used for lossless data compression. The term refers to the use of a variable-length code table for encoding a source symbol (such as a character in a file) where the variable-length code table has been derived in a particular way based on the estimated probability of occurrence for each possible value of the source symbol. It was developed by David A. Huffman while he was a Ph.D. student at MIT, and published in the 1952 paper "A Method for the Construction of Minimum-Redundancy Codes".

Control CPU Usage by using ctypes (Win32 Platform) (Python)

2009-01-26T09:32:34-08:00

Python recipe 576634 by Shao-chuan Wang (cpu_usage, ctypes, system_programming, win32). Revision 3.

This program will make your cpu work at a given cpu usage. It should be also able to work on machines with multi-processors. The program has been tested on Windows xp sp2 with python of version 2.5.4.

The implementation is based on the fact that it will adjust the ratio of being busy over being idle in the main process to approach the target cpu usage rate.