Re: [Tutor] Unpack requires a string argument of length 8
On Mon, May 2, 2011 at 1:17 PM, Marc Tompkins wrote:
> On Mon, May 2, 2011 at 12:36 PM, Susana Iraiis Delgado Rodriguez
> wrote:
>>
>> I'm working on getting information that comes from a dbf file (database),
>> this dbf file is related to another file in the system, a shapefile. My code
>> is trying to get all the dbf name records, but when the systen gets an empty
>> file, my code fails:
>> Traceback (most recent call last):
>> File "", line 1, in
>> File "get_dbf.py", line 32, in
>> dbf = Dbf(d,new=False, readOnly=True)
>> File "C:\Python26\lib\site-packages\dbf.py", line 135, in __init_
>> self.header = self.HeaderClass.fromStream(self.stream)
>> File "C:\Python26\lib\site-packages\header.py", line 109, in from
>> (_cnt, _hdrLen, _recLen) = struct.unpack("> struct.error: unpack requires a string argument of length 8
>> >>>
>> How can I fix it?
>
> You said that this happens when you're trying to process an empty file. If
> that's the case, then I would certainly expect this: "_data[4:12]" not to
> return a string of length 8!
>
> So you have two options:
> - "Get permission"
>>
>> if (some check to make sure the file isn't empty):
>> dbf = Dbf(d,new=False, readOnly=True)
>
> or
> - "Ask forgiveness".
>>
>> try:
>> dbf = Dbf(d,new=False, readOnly=True)
>> except:
>> (cleanup code to handle aborted file opening)
>>
>
> Which is correct? That depends on your own preference, and also on how
> often the error occurs. If you rarely run across empty files, then "ask
> forgiveness" makes more sense, since otherwise you waste time checking for
> an error that hardly ever happens; on the other hand, if you run into lots
> of empty files, then it makes sense to check first, each time.
Also, the first option does leave the possibility of a race condition,
however slim that might be.
Personally, I'd use the try/except pair, and optimize later if it
turned out to be an issue.
--
http://neon-buddha.net
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Re: [Tutor] Medical Decision-Making Question
On Mon, Jun 13, 2011 at 7:22 AM, Fred G wrote: > Hello-- > I'm a pre-med student interested in decision-making as applied to medical > decisions. I am trying to build a medical decision-making algorithm and am > pretty stuck on a few things. > I've built a file that contains a list of many diseases and their associated > symptoms. For example, here are the column headers and two sample rows (the > "|" = "or"): > Disease Symptoms > Cold > sore_throat|runny_nose|congestion|cough|aches|slight_fever > Flu > sore_throat|fever|headache|muscle_aches|soreness|congestion|cough|returning_fever > My questions are the following: > a) How's the best way to make it so I can have a user type in a list of > symptoms and then have the computer tell the user the possible diseases that > share those symptoms? In other words, on a high-level I have a pretty good > idea of what I want my algorithm to do-- but I need help implementing the > basic version first. I'd like to do the following: Please enter a list of symptoms [user_input] Possible diseases include: x, y, z > b)Once I get that working, could anyone point me to good code already > written in Python such that I could have a model (for syntax and overall > structure) for figuring out how to make the computer evaluate more factors > such as: patient age, patient history, and even downloading archival data > for patients in the same demographic group? > Thanks! > > One problem with writing the symptoms is misspelling and word choice, is mild fever the same as slight fever? etc. Another way to do that is to present a list, when the user selects one item in that list, (say, fever, mild) the list is restructured to exclude symptoms that would clash with that, like all the other fevers. After a while of clicking on list items, the evaluator can make a best match against diseases. Downside is a fair amount of processing. You could also group symptoms and have severity as a seperate, so you select fever, then mild,high, whatever. Evaluating it is going to be fun, it's a lot more than binary matches. -- http://neon-buddha.net ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Medical Decision-Making Question
On Mon, Jun 13, 2011 at 3:35 PM, Fred G wrote: > Thanks guys for all the feedback. > re Jim's comments: I completely agree that the difference b/t "slight" fever > and "returning" fever, etc will pose some problems. My hunch is that > initially I'll just do something like make "fever" be the only one for now > w/ the obvious caveat that a few more diseases would not be eliminated than > actually should be. Building on this, another challenging problem will be > how to code the fact that when a symptom occurs early it usually means > something else than if it returns later in the course of an illness. I'm > not 100% sure how I'll handle this, but I think the first priority is > getting access to a dataset and getting the bot up and running before I > focus on this. > re Steve's comments: hmm, sounds like I really should take an AI class. > This problem is just really exciting and driving me, and I'm glad you > pointed out that this will probably take a lot more time than I had > predicted. I'm pretty motivated personally to solve it. I had a few more > questions about your code: > a) Why did you choose not to use a dictionary to store the diseases (keys) > and their possible values (symptoms)? That seemed the most intuitive to me, > like, what I want to do is have it such that we enter in a few symptoms and > then all the keys without those symptoms are automatically eliminated. I've > been off and on teaching myself python for the last 6 months and have > experience in Java. I mean, I think I want a structure like this: If you are going to use dicts, I'd suggest you flip it around, have the symptom be the key, and the list of diseases related to a given symptom, be the value. But that sounds more like a map:reduce problem or an sql query problem than a dict one. I haven't used it in over 20 years, and I was no expert then, but this sounds like a prolog problem :) To maintain the pythonical nature of the list, https://bitbucket.org/cfbolz/pyrolog/ is something I found. Looks interesting. > 1) Main class > -this class calls the diagnose_disease class based on the set of entered > symptoms and demographic information (ie age, location, season (winter, > spring, fall, etc), patient history) > 2) Diagnose_disease class > -this is the heart of the project. Based on the entered symptoms, it keeps > narrowing down the list of possible diseases. Ideally it would ask > follow-up questions of the user to even further narrow down the list of > possible diseases, but that's going to have to wait until I get the rest > working. > 3) Dictionary Class > -this class contains a *dictionary??* of all possible diseases and their > associated symptoms. Assuming in a standardized form for now (such that > "slight_fever" and "returning_fever" are simply coded as "fever" for now, > etc). > does this seem like the best way to go about it? > re: James. I completely agree that my first step should be getting access > to a dataset. I need to know the format, etc of it before I really can > progress on this. > > -- http://neon-buddha.net ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
