python built-in integer object -


i read article python retains number objects better performance. example:

x = 3 y = 3 print(id(x)) print(id(y))

gives out same values, means x , y referencing same object. article suggested retained number objects approximately in range 1~100.

so tested following code getting exact range:

for in range(-1000,1000):     x = int(str(i))     y = int(str(i))     if str(id(x)) == str(id(y)):         print(i)

and result quite weird: prints out -5~256.

i'm wondering how these 2 magic numbers came , why they're being used. also, these 2 values change in different environment? thanks!

256 power of 2 , small enough people using numbers range.

-5 less sure about, perhaps special values?

related: what's integer cache inside python?

also word of wisdom thread:

this implementation detail, don't ever rely on happening or not happening


-

Comments

Post a Comment

Popular posts from this blog

angular - Is it possible to get native element for formControl? -

i've got angular2 reactive form . created formcontrol s , assigned input fields by [formcontrol]=... . understand creates nativeelement <-> formcontrol link. my question: possible nativeelement formcontrol ? wanna myformcontrol.nativeelement.focus() i can share 1 terrible solution works me. in reactive forms can use either 1) formcontroldirective ts mycontrol = new formcontrol('') template <input type="text" [formcontrol]="mycontrol"> or 2) formcontrolname ts myform: formgroup; constructor(private fb: formbuilder) {} ngoninit() { this.myform = this.fb.group({ foo: '' }); } template <form [formgroup]="myform"> <input type="text" formcontrolname="foo"> </form> so these directives write patch like 1) formcontroldirective const originformcontrolngonchanges = formcontroldirective.prototype.ngonchanges; formcontroldirective.proto
Read more

unity3d - Rotate an object to face an opposite direction -

i have object , b. when click on object b, rotates object b (a faces b). b doesn't face a. need following : when faces b, need face opposite direction. have code rotating @ b. how rotate face opposite direction after that? vector3 targetdirection = target - transform.position; float step = speed * time.deltatime; vector3 newdirection = vector3.rotatetowards (turretdome.transform.forward, targetdirection, step, 0.0f); turretdome.transform.rotation = quaternion.lookrotation (newdirection); you object facing object b, want inverse direction of object after that? objecta.transform.rotation = quaternion.inverse(objecta.transform.rotation) but lets assume example turretdome object a, (negate direction): turretdome.transform.rotation = quaternion.lookrotation (-newdirection); naturally, both of these snippets not show how smoothen rotation, seem know how use time.deltatime. just incase unsure, quaternion.lerp this
Read more

javascript - Why jQuery Select box change event is now working? -

i working on product filters user select select box according his/her preference not getting selected value user in jquery. html code:- <select name="product_filter" id="product_filter"> <option value="price_low_first">price : low high</option> <option value="price_high_first">price : high low</option> <option value="latest">latest</option> <option value="popular">most popular</option> </select> jquery code: $(function () { $("#product_filter").change(function () { alert("hi") var selectedtext = $(this).find("option:selected").text(); var selectedvalue = $(this).val(); alert("selected text: " + selectedtext + " value: " + selectedvalue); }); }); hi believe code perfect. once please check jquery.min.js
Read more