Uno (Text-Based) (Python)

2017-07-15T00:46:59-07:00

Python recipe 580811 by Brandon Martin (artificial_intelligence, cards, game, text_game, uno).

A text based recreation of the classic card game featuring functional AIs to play with. Some rules have been modified. User interface is text based, non-curses, using only simple python commands to draw it.

Discrete PID Controller (Python)

2015-12-18T20:59:43-08:00

Python recipe 577231 by Caner (controller, derivative, discrete, integral, pid, proportional, python).

The recipe gives simple implementation of a Discrete Proportional-Integral-Derivative (PID) controller. PID controller gives output value for error between desired reference input and measurement feedback to minimize error value. More information: http://en.wikipedia.org/wiki/PID_controller

For new version please check: https://github.com/ivmech/ivPID

Compute Memory footprint of an object and its contents (Python)

2012-11-23T23:57:31-08:00

Python recipe 577504 by Raymond Hettinger (memory, sizeof). Revision 3.

Recursive version sys.getsizeof(). Extendable with custom handlers.

SortedCollection (Python)

2010-09-01T02:12:33-07:00

Python recipe 577197 by Raymond Hettinger (bisect, collection, sorted). Revision 9.

Wraps bisect.bisect() in an easy to use class that supports key-functions and straight-forward search methods.

Tkinter table with scrollbars (Python)

2017-05-06T19:06:05-07:00

Python recipe 580793 by Miguel Martínez López (scrollbars, table, tkinter). Revision 13.

I created here a tkinter table with scrollbar support. I use one of my other recipes for the mousewheel support and scrolling:

https://code.activestate.com/recipes/580640-scrolling-frame-with-mouse-wheel-support

Frame with border color for Tkinter (Python)

2017-04-17T11:25:02-07:00

Python recipe 580735 by Miguel Martínez López (border, color, frame, tkinter).

This trick show how to add a border color to frame. These are the important configurations:

 highlightbackground="your border color here"
 highlightcolor="your border color here"
 highlightthickness="the border width"
 bd= 0

Shoelace Formula for polygonal area (Python)

2017-07-17T05:53:45-07:00

Python recipe 580812 by Paddy McCarthy (2d, area).

Copied, by author from "Paddy3118 Go deh!: Python investigation of the Shoelace Formula for polygonal area http://paddy3118.blogspot.com/2017/07/python-investigation-of-shoelace.html#ixzz4n43Dqhaa " Where there is more meat on the bone (under a different license though).

Log watcher (tail -F *.log) (Python)

2014-04-04T15:54:03-07:00

Python recipe 577968 by Giampaolo Rodolà (color, log, logging, monitor, python, rotate, rotations, tail). Revision 10.

A python class which "watches" a directory and calls a callback(filename, lines) function every time one of the files being watched gets written, in real time.

Practically speaking, this can be compared to "tail -F *.log" UNIX command, but instead of having lines printed to stdout a python function gets called.

Similarly to tail, it takes care of "watching" new files which are created after initialization and "unwatching" those ones which are removed in the meantime. This means you'll be able to "follow" and support also rotating log files.

History

rev5 (2013-04-05):
- sizehint parameter
rev4 (2013-03-16):
- python 3 support (also dropped support for python <= 2.5)
- windows support
- unit tests
- main class can also be used as a context manager
rev3 (2012-01-13): initial release

Tkinter table (Python)

2017-05-02T21:19:51-07:00

Python recipe 580786 by Miguel Martínez López (table, tkinter). Revision 24.

Table of data for tkinter.

Here there is an improved vesion with vertical scrollbar support:

https://code.activestate.com/recipes/580793-tkinter-table-with-scrollbars

Size of Python objects (revised). (Python)

2017-07-22T15:52:01-07:00

Python recipe 546530 by Jean Brouwers (getsizeof, memory, sizeof). Revision 21.

This recipe determines the size of Python objects in bytes and has been further enhanced to handle ints, namedtuples, arrays and NumPy types better. Functions alen and itemsize have been updated. Support for Python 2.5 and earlier and the tests/examples have been removed. See project Pympler for unit tests.

See also other, simpler recipes like this Compute memory footprint of an object and its contents.

Simple multicolumn listbox for tkinter (Python)

2017-05-02T22:27:15-07:00

Python recipe 580794 by Miguel Martínez López (listbox, multicolumn, table, tkinter).

This recipe makes easy to work a treeview widget like a table.

It has several options for styling:

heading_anchor
heading_font
heading_background
heading_foreground
cell_anchor
cell_background
cell_foreground
cell_font
cell_pady
height
padding
adjust_heading_to_content
stripped_rows
headers
selection_background
selection_foreground
field_background

The "command" parameter is a callback and its called each time a row is selected.

Decorator for BindingConstants at compile time (Python)

2010-11-16T08:36:38-08:00

Python recipe 277940 by Raymond Hettinger (programs). Revision 9.

Decorator for automatic code optimization. If a global is known at compile time, replace it with a constant. Fold tuples of constants into a single constant. Fold constant attribute lookups into a single constant.

LRU and LFU cache decorators (Python)

2010-08-01T01:19:23-07:00

Python recipe 498245 by Raymond Hettinger (shortcuts). Revision 6.

One-line decorator call adds caching to functions with hashable arguments and no keyword arguments. When the maximum size is reached, the least recently used entry or least frequently used entry is discarded -- appropriate for long-running processes which cannot allow caches to grow without bound. Includes built-in performance instrumentation.

Persistent dict with multiple standard file formats (Python)

2011-09-06T20:01:46-07:00

Python recipe 576642 by Raymond Hettinger (dbm, dictionary, persistent, shelve). Revision 10.

dbdict: a dbm based on a dict subclass.

On open, loads full file into memory. On close, writes full dict to disk (atomically). Supported output file formats: csv, json, and pickle. Input file format automatically discovered.

Usable by the shelve module for fast access.

Disk usage (Python)

2012-10-06T15:33:40-07:00

Python recipe 577972 by Giampaolo Rodolà (disk, python, python3, space, statistics, usage). Revision 6.

Provides disk usage statistics (total, used and free disk space) about a given path.

This recipe was initially developed for psutil:

http://code.google.com/p/psutil/issues/detail?id=172

...and then included into shutil module starting from Python 3.3:

The recipe you see here is a modified version of the latter one in that the Windows implementation uses ctypes instead of a C extension module. As such it can be used with python >= 2.5.

Genetic Algorithm in Python source code - AI-Junkie tutorial (Python)

2012-06-19T12:59:13-07:00

Python recipe 578128 by David Adler (algorithm, artificial, genetic, network, neural, python). Revision 5.

A simple genetic algorithm program. I followed this tutorial to make the program http://www.ai-junkie.com/ga/intro/gat1.html.

The objective of the code is to evolve a mathematical expression which calculates a user-defined target integer.

KEY:

chromosome = binary list (this is translated/decoded into a protein in the format number --> operator --> number etc, any genes (chromosome is read in blocks of four) which do not conform to this are ignored.

protein = mathematical expression (this is evaluated from left to right in number + operator blocks of two)

output = output of protein (mathematical expression)

error = inverse of difference between output and target

fitness score = a fraction of sum of of total errors

OTHER:

One-point crossover is used.

I have incorporated elitism in my code, which somewhat deviates from the tutorial but made my code more efficient (top ~7% of population are carried through to next generation)

groupby() For Unsorted Input (Python)

2017-05-12T10:40:58-07:00

Python recipe 580800 by Alfe (algorithm, datastructures, generators, grouping, lazy).

We all know the groupby() which is available in the itertools standard module. This one yields groups of consecutive elements in the input which are meant to be together in one group. For non-consecutive elements this will yield more than one group for the same key.

So effectively, groupby() only reformats a flat list into bunches of elements from that list without reordering anything. In practice this means that for input sorted by key this works perfect, but for unsorted input it might yield several groups for the same key (with groups for other keys in between). Typically needed, though, is a grouping with reordering if necessary.

I implemented a likewise lazy function (yielding generators) which also accepts ungrouped input.

Variable Abbreviations (Python)

2017-06-22T11:57:20-07:00

Python recipe 580807 by Alfe (abbreviations, contextmanager, variables, with).

One sometimes has nice long speaking names vor variables, maybe things like buildingList[foundIndex].height, but would like to address these in a shorter fashion to be used within a formula or similar where lots of longs names tend to confuse any reader trying to understand the formula. Physicists use one-letter names for a reason.

For this I wrote a small context provider which allows using short names instead of long ones:

with Abbr(h=buildingList[foundIndex].height, g=gravitationalConstant):
    fallTime = sqrt(2 * h / g)
    endSpeed = sqrt(2 * h * g)
print("Fall time:", fallTime)
print("End speed:", endSpeed)

For longer formulas this can reduce ugly multi-line expressions to clearly readable one-liners.

One could use this:

h = buildingList[foundIndex].height
g = gravitationalConstant
fallTime = sqrt(2 * h / g)
endSpeed = sqrt(2 * h * g)
del g, h
print("Fall time:", fallTime)
print("End speed:", endSpeed)

to achieve the same result, but

it would not look as clean and
the context provider solves the typical issues like cleanup on exception etc.

Just using local variables without cleanup (like above without the del statement) also is an option of course, but that would clutter the variable name space unnecessarily.

CAVEATS: The implementation of Abbr() is a hack. If used as intended and described here, it should work just fine, though. But the hackish nature forces me to mention some things: Since at compile time the compiler decides that the h and g in the example must be global variables (because they aren't assigned in the function), it produces byte code accessing global variables. The context provider changes the global variable structure to fill the needs. (Overridden already existing global variables of the same name get restored properly at context exit.) This means some things:

One cannot have a local variable of the same name in the frame surrounding the context manager.
Existing global variables are changed during the time of the context manager; so using names like sys or os for abbreviations might be a bad idea due to side-effects.

Equally-spaced numbers (linspace) (Python)

2015-01-12T22:16:37-08:00

Python recipe 579000 by Andrew Barnert (float, linspace, range, spread).

An equivalent of numpy.linspace, but as a pure-Python lazy sequence.

Like NumPy's linspace, but unlike the spread and frange recipes listed here, the num argument specifies the number of values, not the number of intervals, and the range is closed, not half-open.

Although this is primarily designed for floats, it will work for Fraction, Decimal, NumPy arrays (although this would be silly) and even datetime values.

This recipe can also serve as an example for creating lazy sequences.

See the discussion below for caveats.

Super Simple Sudoku Solver in Python source code (Python)

2012-06-23T14:56:05-07:00

Python recipe 578140 by David Adler (algorithm, python, recursive, recurssion, sodoku, sudoku). Revision 5.

A simple algorithm which uses a recursive function to solve the puzzle.

THE ALGORITHM

The credit for this algorithm must go to Richard Buckland: http://www.youtube.com/watch?v=bjObm0hxIYY&feature=autoplay&list=PL6B940F08B9773B9F&playnext=1

Takes a partially filled in grid, inserts the min value in a cell (could be a random cell, in this case the first free cell). If the min value is not legal it will increment until the max value is reached (number 9), checking each time if the incremented value is legal in that cell (ie does not clash with any already entered cells in square, col or row). If it is legal, it will call itself (the hasSolution function) thus using this slightly more filled in grid to find a new cell and check which value is legal in this next cell. If no values are legal in the next cell, it will clear the previous grid entry and try incrementing the value.

isLegal = does not conflict with any other numbers in the same row, column or square

Most viewed recipes tagged "meta:min_python_3=*"