Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.python > #5000 > unrolled thread

Inconsistency with split() - Script, OS, or Package Problem?

Back to article view | Back to comp.lang.python

Contents

  Inconsistency with split() - Script, OS, or Package Problem? James Wright <jamfwright@gmail.com> - 2011-05-09 14:10 -0400
    Re: Inconsistency with split() - Script, OS, or Package Problem? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-05-09 18:43 +0000
      Re: Inconsistency with split() - Script, OS, or Package Problem? James Wright <jamfwright@gmail.com> - 2011-05-09 15:09 -0400
        Re: Inconsistency with split() - Script, OS, or Package Problem? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-05-10 00:00 +0000

#5000 — Inconsistency with split() - Script, OS, or Package Problem?

Hello,

I have been using a script on several boxes that have been around for
a while, and everything works just fine.  I am finding though, that on
some new OS installs the script fails with:

Traceback (most recent call last):
  File "render4.py", line 114, in <module>
    create_report_index(each_item)
  File "render4.py", line 25, in create_report_index
    [clean_name, _] = each_value.split('_', 1)
ValueError: need more than 1 value to unpack


The OS's are various OpenSuse installs from 10.3 to 11.4.  It works on
all the existing ones, which leads me to believe that I have a package
or configuration inconsistency. It should be noted though that I am
quite new to python programming and very well could have coded in a
non-portable manner and was just lucky to get it working in the first
place :)

Here is the code snippet that generates the failure (  when you look
at this remember that I am a novice :-)  ):

for each_item in D4:  #D4 is a dictionary
    create_report_index(each_item)

def create_report_index(report):  #Here we are creating a simple
index.html file from data in a text file
    newfile = open(report + '.html', 'w') #Create the index file using
report name
    for each_value in D4[report]:
        [clean_name, _] = each_value.split('_', 1)
        newfile.write('<a href="' + report +'//' + each_value +
'/index.htm">' + clean_name + '</a><BR>\n')


I've tried to match packages from a known working install and even
compiled a newer python (one known to work, version 3.1.3 in this
particular case).  The only discernible difference is that the new OS
installs are VM's hosted on VMWare ESX.  Using the same ISO I can spin
up a VirtualBox VM and the script works just fine.  I've tried this
with OpenSuse 11.3 and 11.4, once again, using the exact same ISO's to
install.

Do I have a Python, OS, or package issue?


Many thanks,
James

[toc] | [next] | [standalone]

#5005

On Mon, 09 May 2011 14:10:21 -0400, James Wright wrote:

> Hello,
> 
> I have been using a script on several boxes that have been around for a
> while, and everything works just fine.  I am finding though, that on
> some new OS installs the script fails with:
> 
> Traceback (most recent call last):
>   File "render4.py", line 114, in <module>
>     create_report_index(each_item)
>   File "render4.py", line 25, in create_report_index
>     [clean_name, _] = each_value.split('_', 1)
> ValueError: need more than 1 value to unpack

It's a data issue, not an OS or package problem.

Firstly, you don't have to wrap the left hand side in brackets, this 
works fine:

>>> each_value = "aaa_bbb_ccc"
>>> clean_name, _ = each_value.split('_', 1)
>>> clean_name
'aaa'


However, if your data has no underscore at all:

>>> each_value = "aaa*bbb*ccc"
>>> clean_name, _ = each_value.split('_', 1)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: need more than 1 value to unpack



So you need to allow for the possibility that there is no underscore.




-- 
Steven

[toc] | [prev] | [next] | [standalone]

#5008

Thank you Steven,

I will take your advice :)  In this particular case though, I do not
think a lack of underscore is the issue, at least as far as I can
understand the issue.  Please see my reply to Ethan.


Thanks,
James


On Mon, May 9, 2011 at 2:43 PM, Steven D'Aprano
<steve+comp.lang.python@pearwood.info> wrote:
> On Mon, 09 May 2011 14:10:21 -0400, James Wright wrote:
>
>> Hello,
>>
>> I have been using a script on several boxes that have been around for a
>> while, and everything works just fine.  I am finding though, that on
>> some new OS installs the script fails with:
>>
>> Traceback (most recent call last):
>>   File "render4.py", line 114, in <module>
>>     create_report_index(each_item)
>>   File "render4.py", line 25, in create_report_index
>>     [clean_name, _] = each_value.split('_', 1)
>> ValueError: need more than 1 value to unpack
>
> It's a data issue, not an OS or package problem.
>
> Firstly, you don't have to wrap the left hand side in brackets, this
> works fine:
>
>>>> each_value = "aaa_bbb_ccc"
>>>> clean_name, _ = each_value.split('_', 1)
>>>> clean_name
> 'aaa'
>
>
> However, if your data has no underscore at all:
>
>>>> each_value = "aaa*bbb*ccc"
>>>> clean_name, _ = each_value.split('_', 1)
> Traceback (most recent call last):
>  File "<stdin>", line 1, in <module>
> ValueError: need more than 1 value to unpack
>
>
>
> So you need to allow for the possibility that there is no underscore.
>
>
>
>
> --
> Steven
> --
> http://mail.python.org/mailman/listinfo/python-list
>

[toc] | [prev] | [next] | [standalone]

#5041

On Mon, 09 May 2011 15:09:32 -0400, James Wright wrote:

> Thank you Steven,
> 
> I will take your advice :)  In this particular case though, I do not
> think a lack of underscore is the issue, at least as far as I can
> understand the issue.  Please see my reply to Ethan.


In your reply to Ethan, you inserted a print statement in the code and 
got this output:

    # python render4.py
    current each_value is: vsr
    Traceback (most recent call last):
      File "render4.py", line 115, in <module>
        create_report_index(each_item)
      File "render4.py", line 26, in create_report_index
        [clean_name, _] = each_value.split('_', 1)
    ValueError: need more than 1 value to unpack


The current value of each_value is the three letter string "vsr". There 
are no underscores in "vsr". Clearly the lack of underscore is the issue. 
Now that this has been solved, it has revealed a deeper problem, namely, 
how you get an empty key and "vsr" into your data on some machines but 
not others.

If your script is behaving differently on different machines with the 
same data, it is *far* more likely that there is something non-
deterministic in your code than that it is a bug in either the OS, 
Python, or the virtualization environment. Without seeing either your 
code or data, it is impossible to know what.

No offense, but are you sure it's not a PEBCAK error? Are you absolutely 
sure you're running the same script the same way from the same data on 
each virtual machine?

The fact that your script works correctly *once* when you rename it 
doesn't strike me with confidence. Renaming the script shouldn't change 
its behaviour.

I suppose it is just barely plausible that one of the VMs is reading its 
data from faulty sectors on a disk, and hence gets inconsistent results, 
but that is stretching the bounds of possibility almost to breaking.

You posted the data and script to Alex off list. Perhaps you could post 
it again on-list? As they say, many eyes make bugs shallow.


-- 
Steven

[toc] | [prev] | [standalone]

Back to top | Article view | comp.lang.python

csiph-web