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RE: updating dictionaries from/to dictionaries

P: n/a
if the values for any of the keys are None, both do not work as can be seenbelow!!.

since both loops are iterating over keys(), 'get' method which would returna '0' for non existing key does not encounter any non-existing keys.
================================================== ==========
import copy, sys

foo = { 'one' : 1, 'two' : 2, 'three' : None }
bar = copy.deepcopy(foo)

try:
for key in foo:
foo[key] += bar.get(key, 0)
except:
print 'foo', sys.exc_info()[:2]

try:
for key in bar:
foo[key] += bar[key]
except:
print 'bar', sys.exc_info()[:2]
========================================
foo (<type 'exceptions.TypeError'>, TypeError("unsupported operand type(s) for +=: 'NoneType' and 'NoneType'",))
bar (<type 'exceptions.TypeError'>, TypeError("unsupported operand type(s) for +=: 'NoneType' and 'NoneType'",))

hope that helps to clarify both point of views.
thanks Edwin

-----Original Message-----
From: py************************************************ **@python.org
[mailto:py***************************************** *********@python.org]
On Behalf Of Brandon
Sent: Thursday, August 14, 2008 8:35 PM
To: py*********@python.org
Subject: Re: updating dictionaries from/to dictionaries
(1) iterating over foo:
for key in foo:
foo[key] += bar.get(key, 0)

(2) iterating over bar:
for key in bar:
foo[key] += bar[key]

I (again) challenge you to say *why* you feel that the "iterating over
bar" solution will not work.

Well if you're going to be clever enough to iterate over bar and then
send the results to another dictionary altogether, I obviously cannot
put up a good argument on this matter!

Thanks for the input, I appreciate it.
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Aug 15 '08 #1
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P: n/a
On Aug 15, 11:23 am, Edwin.Mad...@VerizonWireless.com wrote:
if the values for any of the keys are None, both do not work as can be seen below!!.
If any of the values are None, nothing can work. The OP justifiably
(given his problem domain (bigram frequencies)) expects that all
values will be integers. If this is not the case, it means that the
code that populates his dictionaries is majorly stuffed, an exception
will be raised, and he can fix it.

Aug 15 '08 #2

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