python - How are finite automata implemented in code? -


how 1 implement dfa or nfa matter in python code?

what ways in python? , ever used in real world projects?

a straightforward way represent dfa dictionary of dictionaries. each state create dictionary keyed letters of alphabet , global dictionary keyed states. example, following dfa wikipedia article on dfas

enter image description here

can represented dictionary this:

dfa = {0:{'0':0, '1':1},        1:{'0':2, '1':0},        2:{'0':1, '1':2}}

to "run" dfa against input string drawn alphabet in question (after specifying initial state , set of accepting values) straightforward:

def accepts(transitions,initial,accepting,s):     state = initial     c in s:         state = transitions[state][c]     return state in accepting

you start in initial state, step through string character character, , @ each step next state. when done stepping through string check if final state in set of accepting states.

for example

>>> accepts(dfa,0,{0},'1011101') true >>> accepts(dfa,0,{0},'10111011') false

for nfas store sets of possible states rather individual states in transition dictionaries , use random module pick next state set of possible states.


Comments

Post a Comment

Popular posts from this blog

javascript - jQuery: Add class depending on URL in the best way -

i have html progress meter: <div class="col-md-3" style="margin-left: -20px;"> <div class="progress-pos active" id="progess-1"> <div class="progress-pos-inner"> login </div> </div> </div> <div class="col-md-3 progress-pos-container"> <div class="progress-pos" id="progess-2"> <div class="progress-pos-inner"> scan items </div> </div> </div> <div class="col-md-3 progress-pos-container"> <div class="progress-pos" id="progess-3"> <div class="progress-pos-inner"> confirm address </div> </div> </div> <div class="col-md-3 progress-pos-container"> <div class="progress-pos" id="progess-4"> <div class="progress-pos-in...
Read more

caching - How to check if a url path exists in the service worker cache -

i need check if particular url path exists in service worker cache. example, suppose url is: /myserviceworker/service?a=110&b=70 this url exists in cache, there many of them different values of , b. now, suppose want refresh of these urls, how can that? i want know how access key values service worker cache. if know key, plan follows: var url = new url(key); if(url.pathname === "\/myserviceworker/service") refetch key but not sure how cache key , in format is. mean, string or url? cache api has match() method returns promise resolving in response object if match or undefined if no match exists. second parameter object can specify ignoresearch not take account url parameters. the ignoresearch option supported firefox ( chrome status here ). in other hand, retrieve cache entries, can use keys() method.
Read more

Redirect to a HTTPS version using .htaccess -

i need modify .htaccess file redirect urls https version without "www". http://example.com --> https://example.com http://www.example.com --> https://example.com https://www.example.com --> https://example.com this how .htaccess file looks like: rewriteengine on rewritecond %{request_filename} !-d rewritecond %{request_filename} !-f rewriterule ^(.*)$ redirect.php?id=$1&page=$2 [qsa,l] what modifications need make .htaccess in order forward https without "www"? it depends on doing current code. looks file called redirect trying display php page seo friendly url. think might confusing people. anyway, need , force https without www, need 1 more rule above. also second rule needs two capture groups in rewriterule test string because wanting 2 different values using $1 , $2 references. rewriteengine on #rediect www non www and/or http https --- combinations. rewritecond %{http_host} !^example\.com [nc,or] rewritecond %{https} !^...
Read more