Popular recipes by yota

nbitarray (Python)

2016-04-21T14:12:33-07:00

Python recipe 580649 by yota .

library to store n bits data (n > 0) in a python array

ed25519 (Python)

2015-09-21T12:58:34-07:00

Python recipe 579102 by yota (cryptography). Revision 2.

This is a re-implementation of the ed25519 signature algorithm as proposed on this page : http://ed25519.cr.yp.to/python/ed25519.py.

Do not use for production, only for the eyes o_O

Code is tab indented, space indentation kills kitten...

least square fitting (Python)

2015-10-03T15:32:28-07:00

Python recipe 579106 by yota (fitting). Revision 2.

a generic python code to fit points to a given curve, was made for a paraboloid, but can be easily expanded to many kind of curves

pick all combinations of items in buckets (Python)

2015-09-05T07:39:42-07:00

Python recipe 579098 by yota (combinatorics).

Let be a number of buckets, containing each, a variable number of items. This function return all combinations possible of one item picked out of each bucket

example, with three buckets {ba, be, bi}, {ka, ko, ku, ke} and {to, ty}, the function enumerate as such:

 0. ba-ka-to
 1. ba-ka-ty
 2. ba-ko-to
 3. ba-ko-ty
 4. ba-ku-to
 5. ba-ku-ty
 6. ba-ke-to
 7. ba-ke-ty
 8. be-ka-to
 9. be-ka-ty
10. be-ko-to
11. be-ko-ty
12. be-ku-to
13. be-ku-ty
14. be-ke-to
15. be-ke-ty
16. bi-ka-to
17. bi-ka-ty
18. bi-ko-to
19. bi-ko-ty
20. bi-ku-to
21. bi-ku-ty
22. bi-ke-to
23. bi-ke-ty

smart copy (Python)

2015-02-06T09:45:12-08:00

Python recipe 579020 by yota (shutil).

take a glob expression, a source directory and a destination directory to copy each files matching the glob in the appropriate directory

glob = */*.txt
src_dir = ./a/b
dst_dir = /z/x/y

if the glob match a file ./a/b/c/foo.txt, it will copy it in /z/x/y/c/foo.txt (and create the missing directory if needed)

Require Python3.4, code tab indented

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

2014-05-15T13:44:15-07:00

Python recipe 578880 by yota (memory, sizeof).

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

Levenshtein, my love (Python)

2014-01-15T09:14:30-08:00

Python recipe 578810 by yota (text). Revision 3.

be kind and comment, especially if you downvote

levenshtein_distance() is an implementation of the iterative algorithm for the levenshtein distance (cf. http://en.wikipedia.org/wiki/Levenshtein_distance#Iterative_with_full_matrix)

levenshtein_sequence() is an attempt to retrieve one of the levenshtein paths (the one that give priority to substitution, deletion, insertion, in this order). The result is a list of tuples made of:

the operation ( =, -, +, * for respectively keep, delete, insert, substitute)
the coordinate in the first
and in the second string.

>>> levenshtein_sequence('saturday', 'sunday')  
[('=', 0, 0), ('-', 1, 0), ('-', 2, 0), ('=', 3, 1), ('*', 4, 2), ('=', 5, 3), ('=', 6, 4), ('=', 7, 5)]
>>> levenshtein_sequence('kitten', 'sitting')
[('*', 0, 0), ('=', 1, 1), ('=', 2, 2), ('=', 3, 3), ('*', 4, 4), ('=', 5, 5), ('+', 5, 6)]

This code is part of foreplays, in a plan I have to improve difflib with alternative SequenceMatchers \o/

/!\ tab indented, as usual.

dynamic mathjax demo page (HTML)

2015-02-12T13:10:17-08:00

HTML recipe 578679 by yota (latex, math, mathjax). Revision 7.

Html web page to preview latex equations rendered by mathjax. demo here

Equations are updated when shift, space or enter keys are pressed, or when the Textarea lose focus.

In the first block you can try inline-style math, in the second one, display-style math.

heap class (Python)

2015-09-17T12:41:15-07:00

Python recipe 578694 by yota (heap). Revision 2.

heapq is a nice python module, but the interface is not so clean. I found a one-liner on this blog, it's as short as possible, but not really pythonic either :) Here is my contribution to a most readable heap class.

find + grep (Bash)

2013-09-17T08:48:07-07:00

Bash recipe 578661 by yota (find, grep, zsh). Revision 2.

look for a text pattern in files defined by a pattern. First argument is passed to the find command, second one to the grep

./find_n_grep.sh '*.py' 'dict'

more over, it sort by date.

easy user input (Python)

2013-09-13T06:34:08-07:00

Python recipe 578552 by yota (input, python3, query, user). Revision 7.

Improvement over Recipe 577058 and cie.

easy_input() function extends the built-in input() function. A question is prompted as well as some expected answers.

The user input can be incomplete (ie. y or ye instead of yes)

If no list of expected answer is provided, default will be "yes/no".
If no default answer is provided, default will be the first expected answer.

Try and see.

Disclaimer: written in python3, meant for *nix shell, indented with tabs

Avoided caveat: If some expected answer have the same beginning, the user can not enter too few letters. Ex: answer = ['continue', 'test', 'testicle'], user can not input t, te or tes because it will be ambiguous. User can however input test, which is not.

longest common substring (Python)

2013-03-05T19:22:31-08:00

Python recipe 578465 by yota (longest_common_substring). Revision 4.

Return, more than the substring itself, the position of the said substring, relative to each string passed in parameter.

String is a generic term. Here, it is an array, any object with __getitem__() method should work.

topological sorting again (Python)

2013-03-06T19:21:11-08:00

Python recipe 578406 by yota (algorithm, graph, python3, sort, topological). Revision 9.

Topological sorting is the answer to the following question : in a direct acyclic graph, how can I pick up nodes "in order", such as upstream nodes are always before downstream ones ? Many solutions may exists, many algorithms too.

Alas, it seems I'm too stupid to understand already proposed recipes on topological sorting. Hopefully I do grasp the "write once, read many" concept.

Here, you will find a plain algorithm, optimized only for code clarity, of a topological sorting for direct acyclic graphs, implemented in python from the pseudo code found on wikipedia:

L ← Empty list that will contain the sorted elements
S ← Set of all nodes with no incoming edges
while S is non-empty do
    remove a node n from S
    insert n into L
    for each node m with an edge e from n to m do
        remove edge e from the graph
        if m has no other incoming edges then
            insert m into S
if graph has edges then
    return error (graph has at least one cycle)
else 
    return L (a topologically sorted order)

Only tested with python3.2, should work with other versions. Be careful, code indented with tabs, since space is evil è_é