Re: [Tutor] adding dictionary values
2009/3/20 Kent Johnson ken...@tds.net 2009/3/20 Emad Nawfal (عماد نوفل) emadnaw...@gmail.com: if I want to do this with more than two dictionaries, the obvious solution for me is to use something like the reduce functions with a list of dictionary names like: dictList = [dict1, dict2, dict3] newDict = reduce(addDicts, dictList) Is this a satisfactory solution? This will do some extra copying, as addDicts() always copies the first argument. You would do better with something like def addToDict(a, b): for k,v in b.iteritems(): a[k] += v return a newDict = reduce(addDictTo, dictList[1:], defaultdict(int, dictList[0])) or rewrite addDicts() to take a variable number of arguments and loop over the args. Kent Thanks Kent and All. I appreciate your helpfulness -- لا أعرف مظلوما تواطأ الناس علي هضمه ولا زهدوا في إنصافه كالحقيقة.محمد الغزالي No victim has ever been more repressed and alienated than the truth Emad Soliman Nawfal Indiana University, Bloomington ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] adding dictionary values
Hi Tutors,
I have two pickled dictionaries containing word counts from two different
corpora. I need to add the values, so that a word count is the sum of both.
If the word man has a count of 2 in corpus A and a count of 3 in corpus B,
then I need a new dictionary that has man: 5. Please let me know whether
the following is correct/incorrect, good/bad, etc.
Your help appreciated:
def addDicts(a, b):
c = {}
for k in a:
if k not in b:
c[k] = a[k]
else:
c[k] = a[k] + b[k]
for k in b:
if k not in a:
c[k] = b[k]
return c
# test this
dict1 = {dad: 3, man: 2}
dict2 = {dad: 5, woman: 10}
newDict = addDicts(dict1, dict2)
print(newDict)
# This gives
{'dad': 8, 'woman': 10, 'man': 2}
--
لا أعرف مظلوما تواطأ الناس علي هضمه ولا زهدوا في إنصافه كالحقيقة.محمد
الغزالي
No victim has ever been more repressed and alienated than the truth
Emad Soliman Nawfal
Indiana University, Bloomington
___
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Re: [Tutor] adding dictionary values
You should iterate over the keys of the dictionary:
for k in a.keys():
because if you iterate over the full dictionary, your items are the values,
not the keys. Otherwise your code looks correct, and I don't think its
terribly bad form. You could do something interesting with sets:
sa = set(a.keys())
sb = set(b.keys())
The next step could be a for loop, but if you enjoy terseness and taking
advantage of language features (also should be faster for big enough dicts):
c = dict( \
[(k, a[k]+b[k]) for k in sasb ] + \
[(k, a[k]) for k in sa-sb ] + \
[(k, b[k]) for k in sb-sa ]
)
which creates a new dict from a list of key, value pairs. The list is a sum
of three lists: those keys in both a and b, those only in a, and those only
in b.
Cheers
On Friday 20 March 2009 10:11, Emad Nawfal wrote:
Hi Tutors,
I have two pickled dictionaries containing word counts from two different
corpora. I need to add the values, so that a word count is the sum of both.
If the word man has a count of 2 in corpus A and a count of 3 in corpus
B, then I need a new dictionary that has man: 5. Please let me know
whether the following is correct/incorrect, good/bad, etc.
Your help appreciated:
def addDicts(a, b):
c = {}
for k in a:
if k not in b:
c[k] = a[k]
else:
c[k] = a[k] + b[k]
for k in b:
if k not in a:
c[k] = b[k]
return c
# test this
dict1 = {dad: 3, man: 2}
dict2 = {dad: 5, woman: 10}
newDict = addDicts(dict1, dict2)
print(newDict)
# This gives
{'dad': 8, 'woman': 10, 'man': 2}
___
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Re: [Tutor] adding dictionary values
2009/3/20 greg whittier g...@thewhittiers.com:
This looks like it will work, but you can accomplish this more compactly by
just looping over the items in both dictionaries and making use of the
default argument of the dictionaries get method.
newDict = {}
for k, v in dict1.items() + dict2.items():
newDict[k] = newDict.get(k,0) + v
Even simpler, start with a copy of dict1:
newDict = dict(dict1)
for k, v in dict2.items():
newDict[k] = newDict.get(k,0) + v
Kent
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Re: [Tutor] adding dictionary values
2009/3/20 Chris Fuller cfuller...@thinkingplanet.net:
You should iterate over the keys of the dictionary:
for k in a.keys():
because if you iterate over the full dictionary, your items are the values,
not the keys. Otherwise your code looks correct, and I don't think its
terribly bad form. You could do something interesting with sets:
sa = set(a.keys())
sb = set(b.keys())
The next step could be a for loop, but if you enjoy terseness and taking
advantage of language features (also should be faster for big enough dicts):
c = dict( \
[(k, a[k]+b[k]) for k in sasb ] + \
[(k, a[k]) for k in sa-sb ] + \
[(k, b[k]) for k in sb-sa ]
)
which creates a new dict from a list of key, value pairs. The list is a sum
of three lists: those keys in both a and b, those only in a, and those only
in b.
Cheers
On Friday 20 March 2009 10:11, Emad Nawfal wrote:
Hi Tutors,
I have two pickled dictionaries containing word counts from two different
corpora. I need to add the values, so that a word count is the sum of both.
If the word man has a count of 2 in corpus A and a count of 3 in corpus
B, then I need a new dictionary that has man: 5. Please let me know
whether the following is correct/incorrect, good/bad, etc.
Your help appreciated:
def addDicts(a, b):
c = {}
for k in a:
if k not in b:
c[k] = a[k]
else:
c[k] = a[k] + b[k]
for k in b:
if k not in a:
c[k] = b[k]
return c
# test this
dict1 = {dad: 3, man: 2}
dict2 = {dad: 5, woman: 10}
newDict = addDicts(dict1, dict2)
print(newDict)
# This gives
{'dad': 8, 'woman': 10, 'man': 2}
___
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Just to add another tool to your toolbox, defaultdicts, available from
version 2.5, are good for word counts, and simplifies your function no
end:
from collections import defaultdict
def addDict(a, b):
newdict = defaultdict(int, a)
for k,v in b.iteritems():
newdict[k] += v
return newdict
you can chage the last line to return dict(newdict) if the returned
value MUST be a dict, but there is very little advantage to doing so
in properly written code.
Extra credit:
To do a word count with a defaultdict is simple:
wordcount = defaultdict(int)
for word in list_of_words:
wordcount[word] += 1
Look it up in the docs if you want details of defaultdict.
--
Richard Roadie Rich Lovely, part of the JNP|UK Famile
www.theJNP.com
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Re: [Tutor] adding dictionary values
2009/3/20 Emad Nawfal (عماد نوفل) emadnaw...@gmail.com: if I want to do this with more than two dictionaries, the obvious solution for me is to use something like the reduce functions with a list of dictionary names like: dictList = [dict1, dict2, dict3] newDict = reduce(addDicts, dictList) Is this a satisfactory solution? This will do some extra copying, as addDicts() always copies the first argument. You would do better with something like def addToDict(a, b): for k,v in b.iteritems(): a[k] += v return a newDict = reduce(addDictTo, dictList[1:], defaultdict(int, dictList[0])) or rewrite addDicts() to take a variable number of arguments and loop over the args. Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
