Re: Django python fuction

[Andrew Farrell]

In general, I recommend adding the line "import pdb;pdb.set_trace()"

to the top of your function and walking through it to see why it doesn't work.

def foo(x):

    import pdb;pdb.set_trace()

    list = []
    if isinstance(x, list):
        for i in x:
            elem = i
            return list + foo(i)
    else:
        return 1

See https://docs.python.org/2/library/pdb.html on how pdb works.

There are faster ways to debug, but when starting out, pdb lets you see what is happening as you run the function.

Some questions I have about this function:

- What is the purpose of the "elem" function? It is never accessed.

- What is the purpose of returning 1 if the argument is not a list?

- Why is it named "foo" rather than something that tells me what the purpose of the function is?

On Tue, Jun 10, 2014 at 8:16 AM, hito koto <hitoko...@gmail.com> wrote:

Hello,

I don't know how can i do to change to write python function
I want to following code change to write python function　or change to write  recursive definition
>>> y = [10, 12, [13, [14, 9], 16], 7]
>>> z = copy.deepcopy(y)
>>> y
[10, 12, [13, [14, 9], 16], 7]
>>> z
[10, 12, [13, [14, 9], 16], 7]
>>> z[2][1][1]
9
>>> z[2][1][1] = 88
>>> z
[10, 12, [13, [14, 88], 16], 7]
[10, 12, [13, [14, 9], 16], 7]
>>>

this is my use function but not work:

def foo(x):
    list = []
    if isinstance(x, list):
        for i in x:
            elem = i
            return list + foo(i)
    else:
        return 1

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[hito koto]

hi,

I have this erroes:

>>> def foo(x):
...     list = []
...     if isinstance(x, list):
...         for i in x:
...             elem = i
...             return list + foo(i)
...     else:
...         return 1
...
>>> foo(a)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 3, in foo
TypeError: isinstance() arg 2 must be a class, type, or tuple of classes and types



2014年6月10日火曜日 22時27分42秒 UTC+9 Andrew Farrell:

[François Schiettecatte]

You are redefining 'list' on line 2, rename list to myList as follows:

def foo(x):
myList = []

if isinstance(x, list):
for i in x:
elem = i

return myList + foo(i)
else:
return 1

And take this to a python list, this is for django.

Cheers

François

> To view this discussion on the web visit https://groups.google.com/d/msgid/django-users/2347967a-55c4-400b-9bf3-7aacc4f27311%40googlegroups.com.

[hito koto]

So, I also have errors:


>>> def foo(x):
...         myList = []

...         if isinstance(x, list):
...                 for i in x:
...                         elem = i

...                 return myList + foo(elem)

...         else:
...                 return 1
...
>>>
>>> foo(a)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>

  File "<stdin>", line 6, in foo
  File "<stdin>", line 6, in foo
TypeError: can only concatenate list (not "int") to list





2014年6月10日火曜日 22時53分28秒 UTC+9 François Schiettecatte:

[François Schiettecatte]

You need to use .append() to add elements to a list, I suggest you take a look at the python tutorial:

https://docs.python.org/2/tutorial/

Not quite sure what you are doing with i or elem either.

François

> To view this discussion on the web visit https://groups.google.com/d/msgid/django-users/4bfaf57c-fd97-4543-b6d1-d479fe3d43e4%40googlegroups.com.

[moqia...@gmail.com]

Hi, hito koto:

I think you want to deep copy the list. The following code maybe  helpful:

def dcopy(obj):

    if not isinstance(obj, list):

        return obj

    return [dcopy(x) for x in obj]

 

But this function only deep copy for list.  You can change code as what I did for dic, set, tuple , etc ..

---

moqia...@gmail.com

To view this discussion on the web visit https://groups.google.com/d/msgid/django-users/7B064353-8567-4B33-BA7C-97BF08A45764%40gmail.com.

[hito koto]

Hi,  Qiancong :

I was looking for exactly this、

Thank you ver much!

2014年6月10日火曜日 23時35分52秒 UTC+9 Qiancong:



[François Schiettecatte]

Wouldn't the deep copy module handle this for you:

https://docs.python.org/2/library/copy.html

François

On Jun 10, 2014, at 12:17 PM, hito koto <hitoko...@gmail.com> wrote:

> Hi, Qiancong :
>
> I was looking for exactly this、
> Thank you ver much!
>
>
> 2014年6月10日火曜日 23時35分52秒 UTC+9 Qiancong:
> 
> Hi, hito koto:
> I think you want to deep copy the list. The following code maybe helpful:
> def dcopy(obj):
> if not isinstance(obj, list):
> return obj
> return [dcopy(x) for x in obj]
>
> But this function only deep copy for list. You can change code as what I did for dic, set, tuple , etc ..

> To view this discussion on the web visit https://groups.google.com/d/msgid/django-users/3015c174-52e5-419c-9854-d089fa533921%40googlegroups.com.

[moqia...@gmail.com]

Yeah, I think hito koto need a function like copy.deepcopy.. I think he known copy.deepcopy before(as his example said),  just not known how to write a funtion work as copy.deecopy does for list.

 

---

To view this discussion on the web visit https://groups.google.com/d/msgid/django-users/D1CD8ADE-6501-4BC6-B1B2-A6C3404D87A6%40gmail.com.

[hito koto]

Thanks

2014年6月11日水曜日 10時37分43秒 UTC+9 Qiancong:



[hito koto]

hi, François :
Thanks

2014年6月11日水曜日 1時22分04秒 UTC+9 François Schiettecatte: