python - How can I quickly find the first element in a list that matches a conditional? -

-

i have 2 subroutines in large program search list first item matches condition , return index. reason, these take large percentage of program's execution time, , wondering how optimize them.

def next_unignored(start_index, ignore, length):     """takes start index, set of indices ignore,         , length of list , finds first index        not in set ignore."""     in xrange(start_index+1, length):         if not in ignore:             return  def last_unignored(start_index, ignore, lower_limit):     """the same other, backwards."""     in xrange(start_index-1, lower_limit-1, -1):         if not in ignore:             return

does have tips on optimizing these routines or others follow similar pattern?

example input:

from sample import next_unignored, last_unignored  start_index = 0 ignore = set([0,1,2,3,5,6,8]) length = 100 print next_unignored(start_index, ignore, length) # => 4  start_index = 8 ignore = set([0,1,2,3,5,6,8]) lower_limit = 0 print last_unignored(start_index, ignore, lower_limit) # => 7 

>>> import numpy np >>> start,length = 0,100 >>> ignore = set([0,1,2,3,5,6,8]) >>> x = np.arange(start,start+length) >>> x[~np.in1d(x,ignore)][0] 4

without numpy

>>> start,length = 0,100 >>> ignore = set([0,1,2,3,5,6,8]) >>> my_list = set(range(start,start+length)) >>> my_list2 = my_list - ignore >>> >>> print max(my_list2) # highest number not in ignore list 99 >>> print min(my_list2)  #lowest value not in ignore list 4

if ignore set sparse method may faster since short circuits if ignore set dense should speed considerably


Comments

Post a Comment

Popular posts from this blog

c# - How Configure Devart dotConnect for SQLite Code First? -

-
can configure following sample code ? when run following code, error : no entity framework provider found ado.net provider invariant name 'devart.data.sqlite' setting in machine.config <system.data> <dbproviderfactories> <add name="dotconnect sqlite" invariant="devart.data.sqlite" description="devart dotconnect sqlite" type="devart.data.sqlite.sqliteproviderfactory, devart.data.sqlite, version=4.6.287.0, culture=neutral, publickeytoken=09af7300eec23701" /> </dbproviderfactories> </system.data> after add below block code in app.config <?xml version="1.0"?> <configuration>   <configsections> <!-- more information on entity framework configuration, visit http://go.microsoft.com/fwlink/?linkid=237468 --> <section name="entityframework" type="system.data.entity.internal.configfile.entityframeworksection, entit...
Read more

c++ - Clear the memory after returning a vector in a function -

-
i have function processes , stores lot of data in , returns results vector of class. amount of data stored in function tremendous , want clear storage memory of function after finished job. necessary (does function automatically clear memory) or should clear memory function? update: vector<customers> process(char* const *filename, vector<int> id) { vector<customers> list_of_customers; (perform actions) return list_of_customers; } variables defined locally within function automatically released @ end of function scope. destructors objects called, should free memory allocated objects (if objects coded correctly). example of such object std::vector . anything you've allocated new must have corresponding delete release storage. try avoid doing own allocation , use raii instead, i.e. containers or smart pointers.
Read more

erlang - Saving a digraph to mnesia is hindered because of its side-effects -

-
updated the digraph library in erlang implements data type side-effectful. each operation on data type saves new state in ets table -- instead of returning altered version of itself, more common in functional languages. the problem usage perspective, impedes effort store or pass around state in convenient way requiring me first "collect" state before can start juggle around. the closest solution have seen far serializer/deserializer , these have drawback tied current structure of digraphs instead of operating on abstract type -- prevents future proof solution. update pascal pointed out serializer utilizes interface of digraph, , hence eliminates drawback mentioned above. better, albeit still inconvenient, see no better alternative. what recommendation on how store digraphs? should go different data type altogether? thanks. i not sure understand concern. fact digraph stored in ets transparent in user interface, might want chnge either exchange digr...
Read more