Problem with dictionary key in Python

Question

For some project I have to make a dictionary in which the keys are urls,among which I have this url:

http://www.microsoft.com/isapi/redir.dll?prd=windows&sbp=mediaplayer&ar=Media&sba=Guide&pver=6.2

the url is too long to fit in here I guess in one single line. I can build a dictionary without any errors this url is also a key. but for some reason when I want to extract the values associated to this key(url). I cannot, I get and error "error key:...." Does someone know what is wrong with this url? Are dictionary keys sensitive to some stuff? thanks

below is the code:

def initialize_sumWTP_table(cursor):
cursor.execute( ''' SELECT url,tagsCount
                     FROM sumWTP''')
rows = cursor.fetchall ()
for url,tagsCount in rows:
    sumWTP[url] = tagsCount

I bet it's nothing to do with the URL specifically - show us your code. — David Z
– David Z, Commented May 16, 2010 at 22:41
gotcha, all good now. (It'd still help to see the code though) — David Z
– David Z, Commented May 16, 2010 at 22:42
also i can easily print the whole dictinary, and also i can access to the items individually, but this key is exception. — Hossein
– Hossein, Commented May 16, 2010 at 22:43
I meant all the code. Where's the line that causes the error? Where is sumWTP initialized? Where's the code that adds the URL to the database? If it's a lot of code, you can post it at some other site like pastebin.net (just for example) and link to it, and then just include the most important few lines here. — David Z
– David Z, Commented May 16, 2010 at 22:49

wisty · Accepted Answer · 2010-05-17 05:23:33Z

1

It is almost inconceivable that the dictionary is "losing" your key. I would guess that there is some small change in the string (case, or how the query string is ordered) that results in the same effective URL, but with a slightly different string.

If this is the case, find a way to "normalize" the URL.

answered May 17, 2010 at 5:23

wisty

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Hossein · Accepted Answer · 2010-05-17 23:25:27Z

1

The problem was a bug in my code. I added some exception handling to solve the problem.The data was right, but I have forgotten to do exception handling in these cases. example:

def getWPT(url,tag):
try:
    row = MemoryInitializer.wtp[url][tag]
except KeyError:
    row = 0
#print row
return row

answered May 17, 2010 at 23:25

Hossein

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Ignacio Vazquez-Abrams · Accepted Answer · 2010-05-16 22:40:37Z

0

The reason for getting a key error when accessing a dict is that the key does not exist. Verify that the key you think exists, and that you're using the correct string.

answered May 16, 2010 at 22:40

Ignacio Vazquez-Abrams

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3 Comments

Hossein Over a year ago

i verified it, i can see it there...when I print the whole dictionary i can see it.

Hossein Over a year ago

i run the code and I can see the keys and values among which is this url, but if I want to access it alone using the key, i can't, other urls work fine.

Ignacio Vazquez-Abrams Over a year ago

That's still saying it. Prove it.

Pierce · Accepted Answer · 2010-05-16 23:37:28Z

0

It's hard to tell based on the code fragment offered. It looks like you are initializing the dictionary. You need to create the sumWTP dictionary first, something like: sumWTP = {}. Then statements like sumWTP[url] = tagcount should work.

answered May 16, 2010 at 23:37

Pierce

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