Summing into a Dictionary

[tbline]

Hi,

Programming in perl and running through lines in a text file, when wanting to sum the area by a key (repeating) variable I am used to using the syntax:
$Hash{$var1}[0] += $area
And then using a foreach loop to get out the total area for each variable.
What is the translation into python for this?

Thanks

[ghostdog74]

Hi,

Programming in perl and running through lines in a text file, when wanting to sum the area by a key (repeating) variable I am used to using the syntax:
$Hash{$var1}[0] += $area
And then using a foreach loop to get out the total area for each variable.
What is the translation into python for this?

Thanks

myDict[var1][0]+=area
 

[tbline]

myDict[var1][0]+=area
 

That is what I have been trying, however when I do, I get the following error:

myDict[au][0]+=area
KeyError: 5

This is the jist of my code so far:

myDict={}
 
for line in f:
        vals = line.strip('\n').split('|')
        stand_num = vals[0]
        access    = vals[3]
        au        = int(vals[7])
        area      = float(vals[9])
 
 
        if au != 99:
                 myDict[au][0]+=area

What does KeyError:5 mean and how I can fix it?

Thanks

[bvdet]

That is what I have been trying, however when I do, I get the following error:

myDict[au][0]+=area
KeyError: 5

This is the jist of my code so far:

myDict={}

for line in f:
vals = line.strip('\n').split('|')
stand_num = vals[0]
access = vals[3]
au = int(vals[7])
area = float(vals[9])


if au != 99:
myDict[au][0]+=area


What does KeyError:5 mean and how I can fix it?

Thanks

myDict does not contain the key 5, therefore the key error. Try this instead:

if myDict.has_key(au):
    myDict[au][0] += area
else:
    myDict[au] = whatever

[bartonc]

That is what I have been trying, however when I do, I get the following error:

myDict[au][0]+=area
KeyError: 5

This is the jist of my code so far:

myDict={}
 
for line in f:
        vals = line.strip('\n').split('|')
        stand_num = vals[0]
        access    = vals[3]
        au        = int(vals[7])
        area      = float(vals[9])
 
 
        if au != 99:
                 myDict[au][0]+=area

What does KeyError:5 mean and how I can fix it?

Thanks

See how much nicer it looks when CODE tags are used. To learn how to use them, look to the right. Third point down under REPLY GUIDELINES. Thanks for taking the time,
Moderator

[elbin]

myDict does not contain the key 5, therefore the key error. Try this instead:

if myDict.has_key(au):
    myDict[au][0] += area
else:
    myDict[au] = whatever

And the 'whatever' should be a list with the area if you're going to use the [0] index:

if myDict.has_key(au):
    myDict[au][0] += area
else:
    myDict[au] = [area]

Or simpler (no index if there will be only one value):

if myDict.has_key(au):
    myDict[au] += area
else:
    myDict[au] = area

OR simpler still ;) :

myDict[au] = myDict.get(au, 0) + area

get() gives you the value of myDict[au], or 0 if it does not exist.