Re: [Tutor] Tutor Digest, Vol 146, Issue 9
Hi, there is one place i think you have to have a look at it and it's the python official site. One thing i love about python is the so well written documentation, i remember when i was learning ruby and had to go to the official doc! it was hard to understand for the beginner how i was. so, here is the link https://docs.python.org/3/tutorial/index.html Good luck Regards ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Understanding error in recursive function
Hi Tom,
You can see what happens for yourself in the Pythontutor:
http://goo.gl/YVkh03 - step through the code by clicking on "Forward" and
see what happens. You are calling the howMany function from inside the
function itself, which is called recursion. This can be practical, but in
your case it isn't. In other langauges, the function would call itself
until you run out of memory, but in Python there is an (adjustable) limit
to the number of recursion that can be executed, before the error occurs
that you describe.
One simple rewrite of your function that counts alle elements of all lists
in the dictionary (I am not sur if that's what you want, but I guess you
can figure out what you need from the example) is this: http://goo.gl/frZfkc
animals = { 'a': ['aardvark'], 'b': ['baboon'], 'c': ['coati']}
x = animals['a']
def how_many(aDict):
count = 0
for value in animals.values():
count += len(value)
return count
print(how_many(x))
(hope the pasted code is not mangled ...)
cheers
Oliver
On Sat, 9 Apr 2016 at 00:52 Tom Maher wrote:
> Hi,
>
> As a test I am trying to write a function that returns the sum of values
> attached to one key in a dictionary. I am wondering why the code that I
> wrote is returning:
> "maximum recursion depth exceeded "
> Here is the code:
>
> animals = { 'a': ['aardvark'], 'b': ['baboon'], 'c': ['coati']}
>
> x = animals['a']
>
> def howMany(aDict):
>
> count = 0
>
> for value in howMany(aDict):
>
>count += 1
>
> return count
>
> howMany(x)
>
>
> Just wondering why I would be getting that error.
>
>
> Thanks
> ___
> Tutor maillist - Tutor@python.org
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>
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Re: [Tutor] Understanding error in recursive function
Hi, I think your function runs forever because the only thing it done is calling it self when entering the for loop when you call your function in the for loop it jump to the definition (def howMany(aDict)) then initialise count and bond the value 0 to it then enter a for loop then call the function 'howMany' again and so on! before the for loop there is nothing happening to the function you defined or the argument is not modified in the recursive call, so i don't understand why you used a recursion there! i think you have to replace the howMany(aDict) in the for loop by aDict it self and it will be ok. for value in aDict: ... Regards ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Understanding error in recursive function
On 08/04/2016 21:48, Tom Maher wrote:
Hi,
As a test I am trying to write a function that returns the sum of values
attached to one key in a dictionary. I am wondering why the code that I
wrote is returning:
"maximum recursion depth exceeded"
Here is the code:
animals = { 'a': ['aardvark'], 'b': ['baboon'], 'c': ['coati']}
x = animals['a']
def howMany(aDict):
count = 0
for value in howMany(aDict):
count += 1
return count
howMany(x)
Just wondering why I would be getting that error.
Thanks
howMany calls howMany which calls howMany...
--
My fellow Pythonistas, ask not what our language can do for you, ask
what you can do for our language.
Mark Lawrence
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