Python function returning correct result but interpreter returning strange error -

-

python newbie here, bear me...

i'm attempting utilize poorly written codeacademy python tutorial, wherein exercise challenge to:

write function called digit_sum takes positive integer n input , returns sum of number's digits.

for example: digit_sum(1234) should return 10 1 + 2 + 3 + 4.

(assume number given positive.)

so, attempt solve challenge writing following code: 

userinput = raw_input("please enter number string here: ") n = userinput lst = list(n) usernumbers = []  def digit_sum(n):     in lst:         b = int(i)         usernumbers.append(b)     numsum = sum(usernumbers)     return numsum  print "this total: %s" % digit_sum(n)

in console exercise, seems work expected:

please enter number string here: 123 total: 6 none

however, interpreter returns error (despite console seeming work properly):

oops, try again. function fails on digit_sum(434). returns 18 when should return 11.

why in heck error being returned? can elucidate what's happening here?

unfortunately, there's no 1 ask @ codeacademy, have post question other students read, not getting insights there.

you not understand variable scoping or types. that's "problem". (it's not problem, since you're learning.)

what's expected

the question wants provide function digit_sum accepts number, , returns number. in case accept 434 , return 18. is, digit_sum(434) = 18.

what you're doing

reading keyboard (raw_input) , printing (print) not related question.

if remove non-function parts of solution, have:

def digit_sum(n):     in lst:         b = int(i)         usernumbers.append(b)     numsum = sum(usernumbers)     return numsum

when try submit this, problems become apparent:

  1. lst not defined.
  2. usernumbers not defined.
  3. you expect string (str) , not number (int)

addressing issues

  1. we have move definition of usernumbers , lst function digit_sum. if set @ "top" level, not reset each time call function, , that's why codecademy isn't getting correct answer.

    the code use check yours like:

    if digit_sum(434) != 18:     print "it should have been 18, got %s" % digit_sum(434)

    they have many such calls, , each subsequent call not change value of lst or usernumbers.

  2. this masks error: digit_sum function accepts string. is, calling (after incorporating fixes #1 above) digit_sum(434) codecademy does, result in error, since expect called digit_sum("434").

a possible solution

the following function based on yours, altered advice above:

def digit_sum(n):     lst = list(str(n))     usernumbers = []     in lst:         b = int(i)         usernumbers.append(b)     numsum = sum(usernumbers)     return numsum

you'll notice other stuff missing: can add in, it's unnecessary. might want use following test while developing:

def digit_sum(n):     lst = list(str(n))     usernumbers = []     in lst:         b = int(i)         usernumbers.append(b)     numsum = sum(usernumbers)     return numsum  print "digit_sum(%s) = %s" % (434, digit_sum(434)) print "digit_sum(%s) = %s" % (123, digit_sum(123)) print "digit_sum(%s) = %s" % (555, digit_sum(555)) print "digit_sum(%s) = %s" % (18, digit_sum(18)) print "digit_sum(%s) = %s" % (1001, digit_sum(1001))

when run it, yields:

digit_sum(434) = 11 digit_sum(123) = 6 digit_sum(555) = 15 digit_sum(18) = 9 digit_sum(1001) = 2

the news these results correct, you're off start! 1 thing you'll learn small, tedious details matter lot in programming.

a small note

it's not easy or obvious. so-called experts started @ zero, , had learn , make mistakes well. don't discouraged! there a lot of disparate concepts have understand know 100% what's happening. nobody gets @ once.

i respect you're trying learn , grow tremendously, fact you're willing ask questions. it's never easy, little burn might getting in brain when try understand of learning feels like. embrace it! ask questions!

good luck learning!

other resources

  1. if may, recommend zed shaw's learn python hard way quality, free supplement learning journey. it's excellent!
  2. i've found udacity's free online courses magnificent resource learning lot of different things. specifically, "intro"-level cs courses in python, , worth time.
  3. peter norvig's essay "teach programming in ten years" considered classic. it's going long journey, enjoy it!

again, luck.


Comments

Post a Comment

Popular posts from this blog

Java 3D LWJGL collision -

-
i making 3d java game lwjgl library, , wondering how add collision detection, player not go through models. i using obj models. here objloader class, loads models: package renderengine; import java.io.bufferedreader; import java.io.file; import java.io.filenotfoundexception; import java.io.filereader; import java.util.arraylist; import java.util.list; import models.rawmodel; import org.lwjgl.util.vector.vector2f; import org.lwjgl.util.vector.vector3f; public class objloader { public static rawmodel loadobjmodel(string filename, loader loader){ filereader fr = null; try { fr = new filereader(new file("res/"+filename+".obj")); } catch (filenotfoundexception e) { system.err.println("couldn't load file!"); e.printstacktrace(); } bufferedreader reader = new bufferedreader(fr); string line; list<vector3f> vertices = new arraylist<vector3f...
Read more

spring - SubProtocolWebSocketHandler - No handlers -

-
i have ugly error during deploying spring app on jboss. 18:11:16,025 error [org.apache.catalina.core.containerbase.[jboss.web].[default-host].[/consumer]] (msc service thread 1-7) exception sending context initialized event listener instance of class org.springframework.web.context.contextloaderlistener: org.springframework.context.applicationcontextexception: failed start bean 'subprotocolwebsockethandler'; nested exception java.lang.illegalargumentexception: no handlers @ org.springframework.context.support.defaultlifecycleprocessor.dostart(defaultlifecycleprocessor.java:176) [spring-context-4.1.3.release.jar:4.1.3.release] @ org.springframework.context.support.defaultlifecycleprocessor.access$200(defaultlifecycleprocessor.java:51) [spring-context-4.1.3.release.jar:4.1.3.release] @ org.springframework.context.support.defaultlifecycleprocessor$lifecyclegroup.start(defaultlifecycleprocessor.java:346) [spring-context-4.1.3.release.jar:4.1.3.release] @ org.s...
Read more

methods - python can't use function in submodule -

-
my folder structure this: pythonstuff/ program.py modulea/ __init__.py foo.py bar.py here's code bar.py : def hello(): print("hello, world!") here's code program.py : #!/usr/bin/env python3 modulea import bar bar.hello() i run $ python3 program.py somehow error: file "program.py", line 3, in <module> bar.hello() attributeerror: 'module' object has no attribute 'hello' edit: __init__.py file empty. edit2: after trying realized had bar.py in root directory contained hello() method. bar.py in modulea/ directory empty. add it import os __all__ = [] module in os.listdir(os.path.dirname(__file__)): if module != '__init__.py' , module[-3:] == '.py': __all__.append(module[:-3]) the init .py files required make python treat directories containing packages; done prevent directories common name, such string, unintentionally hiding v...
Read more