Topics by Gribouillis

This snippet defines a function restart_program() which restarts your python program from within your python program.

This snippets contains a python program to find a shortest solution to the problem of the farmer who whishes to cross a river. The boat can only contain two things, including the rower. The farmer comes with a wolf, a duck and a bag of corn, and he can't leave …

This snippet defines a function returning new identifiers created from reading the computer's time.

I uploaded a module named [symboldict](https://pypi.python.org/pypi/symboldict) to the python package index (pypi). This snippet shows how to use it to create a dictionary of symbols from various modules. This dictionary can be used as a common language shared by several modules. It can be used to load python libraries in …

Sometimes you want the value of a variable to be related to its name in the source code. For example, the variable x should have the value "var x". This is especially useful when you perform symbolic computations with python (with the sympy module for example). In standard python, the …

This snippet defines a function `printat()` which adds line and file information to the normal `print()` function output. The intended use is a quick and dirty debugging information for everyday's use. A more complete solution is to use a logging/debugging/tracing framework.

A feature of the doctest module can be useful when people copy and paste their idle window in the python forum: the ability to transform an example from the python interpreter into python code without the prompts [icode]>>>, ...[/icode] and the output messages. The script below permits to use this …

This snippet defines a function [icode]mousepos()[/icode] which gets the mouse position on the screen. The package python-xlib is required.

This snippet implements a pointed set, that is to say an ordinary set of elements with a distinguished element called the basepoint of the set. For example the seven days of the week could be stored in a pointed set, the basepoint being monday because today is monday. It is …

This small script named `sourcecode.py` is a command line tool to open a python module's source file with the default editor. For example the line $ python sourcecode.py xml.dom.minidom opens the file minidom.py from the python distribution with the default editor. The same works with user-defined modules having a python …

This snippet shows how to find the complex roots of a polynomial using python (tested with python 2.6). You need the scipy or numpy module.

This script computes the formal series expansion of a mathematical function on the command line using the python module swiginac, an interface to the CAS Ginac. Typical invocation in a linux terminal looks like $ serexp.py -n 7 "log(1+x)*(1+x+x**2)**(-1)" 1*x+(-3/2)*x**2+5/6*x**3+5/12*x**4+(-21/20)*x**5+7/15*x**6+Order(x**7) As far as I know, swiginac does not work in …

This python script prints all the columns of an sqlite database which path is given as argument.

The title says it all.

This snippet prints a python list of strings in multicolumn format (similarly to linux `ls` command). It uses module prettytable, available in [pypi](https://pypi.python.org/pypi/PrettyTable).

This snippet is reserved for users of the KDE linux desktop. It adds a *service menu* to kde applications such as dolphin and konqueror, to launch an ipython dashboard in a directory in one click. More specifically, save the text of this snippet as a file `~/.kde/share/kde4/services/ServiceMenus/opennotebook.desktop` (create the directory …

You can teach your linux system that executable python files must be executed with /usr/bin/python. This allows you to write python scripts without the shebang line [icode]#!/usr/bin/env python[/icode]. This snippet shows you how to do it !

The syntax of the [icode]str.format()[/icode] method described in [url=http://docs.python.org/library/string.html#formatstrings]the python 2.6 documentation[/url] looks both powerful and complex. The idea of this thread is to start a collection of nice formatting examples which will ease the task of mastering this function. Please post useful examples, and document them :)

This snippet defines a Print function which can be used with python 2.4, 2.5, 2.6 and 3.0 (for 3.0 this is just the built-in print function). It's interface is that of the python 3.0's print. It simplifies the task of writing transitional code which runs under python 2.5 and python …

This small python script invokes the [Treeline](http://treeline.bellz.org/index.html) tree visualizer to display xml files in a pleasant way. 

This snippet is easy: it defines an immutable wrapper around a sequence type (list, deque, etc) which allows a class, function or module to expose a read only version of a sequence to the outer world. A constant wrapper around mapping types could also be defined in a similar manner.

This python 2.7 snippet adds a thin layer of sugar on the itertools module's api, allowing many of its functions to be used as decorators and adding some new functions. Enjoy !

This snippet defines a `dir()` function which extends python's builtin `dir()` function by adding options to filter the returned sequence of strings by the means of regular expressions. The main use case is live inspection of python objects and modules during an interactive session with the python interpreter. The idea …

This snippet allows one to implement an equivalent of a `__getattr__()` function in a python module. The module can then define its own way to lazily import abitrary symbols. For example the module can contain infinitely many names or load values from other modules on demand. There are many implementations …

When working whith large data files, it may be desirable to output a sequence of bytes by large chunks. This snippet defines a file adapter class to handle this transparently. Writing bytes to an ChunkedOutputFile will automatically write the underlying file object by fixed length chunks.

This python 2 code snippet uses unicode chess symbols and box drawings symbols to display a chessboard in a terminal. With a terminal profile having a monospace font of size 20 or more, it looks quite usable to play chess.

This code snippet provides methods to convert between various ieee754 floating point numbers format. For example double precision to single precision. The format is given by a pair (w, p) giving the size in bits of the exponent part and the significand part in the ieee754 representation of a number …

I discovered and installed a firefox addon called Remote Control. This addon starts a telnet server which lets you send javascript commands to the firefox web browser. Combined with python telnetlib module, it becomes very easy to reload or change the content of a tab in a running firefox from …

These two functions compute the orders of the lowest bit and the highest bit set in the binary representation of an integer. I expect them to handle securely very large integer values.

This snippet defines a decorator @mixedmethod similar to @classmethod, which allows the method to access the calling instance when it exists. The decorated functions have two implicit arguments [i]self, cls[/i], the former having a None value when there is no instance in the call. Using python's descriptor protocol, the implementation …

This snippet defines a function walk() which generically performs a depth-first traversal of a tree, using preorder, inorder or postorder rules. Here, genericity means here that there are no hypotheses on what the tree nodes are or the implementation of the tree. Walk() only needs an arbitrary object used as …

This snippet defines a simple decorator to post-process a function's return value through a sequence of filters. As a first application, the decorator can transform a generator function into a function returning a sequence type (list, tuple, dict).

This snippet defines a decorator to automate attributes setting in class instances at creation time. It can be seen as a gadget feature but it can also be handy especially for fast class prototyping.

Any sequence of python strings can be disguised to look like a file opened for reading, which can then be passed on the fly to functions expecting such an input file. This code snippet defines the necessary adapter class. The obtained file-like objects store only one string of the sequence …

This snippet composes functions of the form [icode]func(infile, outfile)[/icode] which read an input file and transform its content to write an output file. A function [icode]compose((f, g, h,...))[/icode] is defined which returns a new such file transformation function which successively applies f, g, h, using in-memory temporary files.

Sometimes, you just want to run a system command from python and capture its output. Currently, the standard way to do this is to call the subprocess.Popen with convenient arguments and use the communicate method. After writing such code a few times, I wrote this little Command class to ease …

How to create a png image containing a fragment of source code ? Well, don't do it yourself, the [url=http://pygments.org]pygments module[/url] contains all the necessary tools. The example below shows how to produce a png image from python code, but pygments supports lexers for many other languages and its formatter …

A functor, or function object is sometimes a convenient way to encapsulate helper functions and data needed to achieve a small task, and also to share data between calls to the same function. This snippet defines a base class [b]functor[/b] which permits an easy functor creation for python 2.

This snippet defines a context [icode]autofilename()[/icode] to create an existing temporary file with a new name in python. Unlike the methods in the [icode]tempfile[/icode] module, it only gives a filename which exists within a 'with' block, instead of an open file. This is useful for example when a program needs …

This snippet defines a function [icode]a2bits[/icode] which converts a characters string to a string of 0's and 1's showing its bitwise representation.

This snippet generates the best rational approximations of a floating point number, using the method of continued fractions (tested with python 2.6 and 3.1).

This snippet defines a function to merge sorted iterables containing similar items into a single iterable. Items are supposed to be sorted in ascending order. Only one item per iterable is stored at a time.

This snippet defines 3 functions to create in a few seconds an image of a graph containing arbitrary python objects. It uses the module pygraphviz (available at [url]http://pypi.python.org/pypi/pygraphviz/[/url]). See the example use case at the end of the module.

The with statement allows all sorts of syntactic sugar in python. This snippet defines two contexts: [icode]inevitably[/icode] and [icode]preferably[/icode] which register a function call to be executed at the end of a block of statement. Although they are not very useful (the function call could be written directly at the …

This snippet defines a function [icode]exc_browse()[/icode] which displays the current python exception in the web browser. This can be useful to non web programmers who want a nicely displayed exception traceback (web frameworks usually include this feature). The idea of this function is to store the html code generated by …

This snippet defines a class LebsegueSet which instances represent sets of real numbers, namely finite unions of intervals. Set theoretical, topological and measure theoretical operations are implemented in pure python. Use freely and enjoy !

This snippet defines a class OptCmd which adds line and options parsing capabilities to the python standard lib's cmd.Cmd class. It allows you to quickly write an extensible command line interpreter. To use this module, you will need [url=http://www.daniweb.com/code/snippet234768.html]this other code snippet[/url], saved as a module named 'argv.py'. Enjoy the …

Some time ago, I was writing a small command line interpreter, with the help of [url=http://docs.python.org/library/cmd.html#module-cmd]the standard module cmd[/url] which offers minimal support for such tasks, and I had the problem that this module doesn't have a function to parse a command line to produce a list argv which can …

This snippet provides 2 functions to create in memory a gziped archive of a sequence of files and directories, and to extract files from this archive. These functions are similar in effect to the linux commands [icode]tar czf[/icode] and [icode]tar xzf[/icode] but instead of writing an archive file on disk, …