python 2.7 - Extratcing all square submatrices from matrix using Numpy -

-

say have nxn numpy matrix. looking fastest way of extracting square chunks (sub-matrices) matrix. meaning cxc parts of original matrix 0 < c < n+1. sub-matrices should correspond contiguous rows/columns indexes of original matrix. want achieve in little time possible.

you use numpy slicing,

import numpy np  n = 20 x = np.random.rand(n, n)  slice_list = [slice(k, l) k in range(0, n) l in range(k, n)]  results = [x[sl,sl] sl in slice_list]

avoiding loops in numpy, not goal itself. long being mindful it, there shouldn't overhead.


Comments

Post a Comment

Popular posts from this blog

PHP DOM loadHTML() method unusual warning -

-
i had following code works fine on localhost: $document = new domdocument(); $document->loadhtml($p_result); $form = $document->getelementsbytagname('form')->item(0); // code continues using $form variable after same code updated on outside server, loadhtml() failed , issued warning. warning: domdocument::loadhtml() expects parameter 1 valid path, string given in path/name/to/script.php returned null instead of object code pretty gets fatal error. note contents of $p_result absolutely same on outside server , on localhost. but why displays kind of warning , why not work? doesn't loadhtml() expects argument 1 string in first place? why method expects parameter 1 valid path ? just make clear i'm not calling loadhtmlfile() , i'm calling loadhtml() . thanks. you're affected one of php bugs . issue present in php 5.6.8 , 5.6.9. have affected php version on server, , bug-free version on localhost. the bug forbids null
Read more

python - How to create jsonb index using GIN on SQLAlchemy? -

-
here's current code creating index jsonb. index("mytable_data_idx_id_key", mytable.data['id'].astext, postgresql_using='gin') but got error. sqlalchemy.exc.programmingerror: (psycopg2.programmingerror) data type text has no default operator class access method "gin" hint: must specify operator class index or define default operator class data type. [sql: "create index event_data_idx_id_key on event using gin ((data ->> 'id'))"] is there way create index on sqlalchemy? the postgresql specific sqlalchemy docs @ http://docs.sqlalchemy.org/en/latest/dialects/postgresql.html#operator-classes mention postgresql_ops dictionary provide "operator class" used postgresql, , provide example illustrating use: index('my_index', my_table.c.id, my_table.c.data, postgresql_ops={ 'data': 'text_pattern_ops',
Read more

c# - TransactionScope not rolling back although no complete() is called -

-
i'm using transactionscope rollback transaction fail bool errorreported = false; action<importerrorlog> newerrorcallback = e => { errorreported = true; errorcallback(e); }; using (var transaction = new transactionscope()) { foreach (importtaskdefinition task in taskdefinition) { loader.load(streamfile, newerrorcallback, task.destinationtable, processingtaskid); } if (!errorreported) transaction.complete(); } i'm sure there no transactionscope started ahead or after code. i'm using entity framework insert in db. regardless state of errorreported transaction never rolled in case of error. what missing ? transactionscope sets transaction.current . that's does. wants transacted must @ property. i believe ef each time connection opened reason. probably, connection open when scope installed. open connection inside of scope or enlist manually. ef has nasty "design decision": default opens
Read more