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Combining Multiple Element Dictionaries

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chase32

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Combining Multiple Element Dictionaries

Sep 15th, 2009

I am trying to combine two multi-element dictionaries but am running into a problem.

From the example below, what I expected was the dictionary x to contain all three unique combinations.

What seems to have happened is that the y dictionary overwrote the x dictionary.

Am I just using this wrong? Is there a elegant way to add two multi element dictionaies?
thanks!

 Help with Code Tags 
 Python Syntax (Toggle Plain Text) 
>>> x=nested_dict()
>>> y=nested_dict()
>>> 
>>> x[1][1]=1
>>> x[1][2]=2
>>> y[1][3]=3
>>> x.update(y)
>>> print x
defaultdict(<class 'nested_dict.nested_dict'>, {1: defaultdict(<class 'nested_dict.nested_dict'>, {3: 3})})
>>> x=nested_dict()
>>> y=nested_dict()
>>> 
>>> x[1][1]=1
>>> x[1][2]=2
>>> y[1][3]=3
>>> x.update(y)
>>> print x
defaultdict(<class 'nested_dict.nested_dict'>, {1: defaultdict(<class 'nested_dict.nested_dict'>, {3: 3})})

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woooee

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Re: Combining Multiple Element Dictionaries

Sep 15th, 2009

This is correct, as you are updating x[1], that is y's key is also 1 and so overwrite's whatever is in x for that key. Change to
y[2][3]=3
or use
x[1].update(y[1])
and you should get what you expect.. If that's not satisfactory then you will have to write your own routine to update however you want.

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chase32

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Re: Combining Multiple Element Dictionaries

Sep 16th, 2009

Thanks!

the

 Help with Code Tags 
 Python Syntax (Toggle Plain Text) 
x[1].update(y[1])
x[1].update(y[1])

format should work.

If I walk through the keys of Y and use the same value for the key of X, that should let me merge two arbitrary two element dictionaries

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woooee

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Re: Combining Multiple Element Dictionaries

Sep 16th, 2009

Indeed it should, but test for "key in x" as well, or use a try/except, as you can never tell. Please mark this "solved" so no wastes their time on a solved thread.

Edit: I just did the following and it worked fine so you don't have to test for "key in x" as update takes care of that for you.

 Help with Code Tags 
 Python Syntax (Toggle Plain Text) 
x = {}
x[1] = {}
x[1][1]=1
x[1][2]=2
 
y = {}
y[2] = {}
y[2][3]=3
x.update(y)
print x
#
# prints
{1: {1: 1, 2: 2}, 2: {3: 3}}
x = {}
x[1] = {}
x[1][1]=1
x[1][2]=2

y = {}
y[2] = {}
y[2][3]=3
x.update(y)
print x
#
# prints
{1: {1: 1, 2: 2}, 2: {3: 3}}

Last edited by woooee; Sep 16th, 2009 at 1:13 am.

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chase32

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Re: Combining Multiple Element Dictionaries

Sep 16th, 2009

Marked as solved. Thanks for the help!

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chase32

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Re: Combining Multiple Element Dictionaries

Sep 16th, 2009

This is what I ended up with, works great

 Help with Code Tags 
 Python Syntax (Toggle Plain Text) 
def merge(lib1,lib2):
    for item in lib2.keys():
        lib1[item].update(lib2[item])
    return lib1
def merge(lib1,lib2):
    for item in lib2.keys():
        lib1[item].update(lib2[item])
    return lib1

Last edited by chase32; Sep 16th, 2009 at 1:22 pm.

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Re: Combining Multiple Element Dictionaries

Sep 16th, 2009

•

Originally Posted by chase32

This is what I ended up with, works great
Help with Code Tags

Python Syntax (Toggle Plain Text)
def merge(lib1,lib2):
    for item in lib2.keys():
        lib1[item].update(lib2[item])
    return lib1
def merge(lib1,lib2): for item in lib2.keys(): lib1[item].update(lib2[item]) return lib1

Mild caveat, for this to work lib1 and lib2 have to be of type collections.defaultdict(dict) , and each value has to be a dictionary too.

Here is a typical eaxmple ...

 Help with Code Tags 
 python Syntax (Toggle Plain Text) 
# merge two dictionaries and handle key collisions with 
# collections.defaultdict(dict)
 
import collections
 
def merge(lib1, lib2):
    for item in lib2.keys():
        lib1[item].update(lib2[item])
    return lib1
 
d1 = {'a':{1:11}, 'b':{2:22}, 'c':{3:33}}
d2 = {'d':{4:44}, 'c':{5:55}, 'e':{6:66}}
 
# mutliple values go into a dictionary
lib1 = collections.defaultdict(dict)
lib2 = collections.defaultdict(dict)
 
# convert each dict to a defaultdict
lib1.update(d1)
lib2.update(d2)
 
print(lib1)
print(lib2)
print('-'*60)
print( merge(lib1, lib2) )
 
"""my result (notice key 'c')-->
defaultdict(<type 'dict'>, {'a': {1: 11}, 'c': {3: 33}, 'b': {2: 22}})
defaultdict(<type 'dict'>, {'c': {5: 55}, 'e': {6: 66}, 'd': {4: 44}})
------------------------------------------------------------
defaultdict(<type 'dict'>, {'a': {1: 11}, 'c': {3: 33, 5: 55}, 
'b': {2: 22}, 'e': {6: 66}, 'd': {4: 44}})
"""
# merge two dictionaries and handle key collisions with 
# collections.defaultdict(dict)

import collections

def merge(lib1, lib2):
    for item in lib2.keys():
        lib1[item].update(lib2[item])
    return lib1

d1 = {'a':{1:11}, 'b':{2:22}, 'c':{3:33}}
d2 = {'d':{4:44}, 'c':{5:55}, 'e':{6:66}}

# mutliple values go into a dictionary
lib1 = collections.defaultdict(dict)
lib2 = collections.defaultdict(dict)

# convert each dict to a defaultdict
lib1.update(d1)
lib2.update(d2)

print(lib1)
print(lib2)
print('-'*60)
print( merge(lib1, lib2) )

"""my result (notice key 'c')-->
defaultdict(<type 'dict'>, {'a': {1: 11}, 'c': {3: 33}, 'b': {2: 22}})
defaultdict(<type 'dict'>, {'c': {5: 55}, 'e': {6: 66}, 'd': {4: 44}})
------------------------------------------------------------
defaultdict(<type 'dict'>, {'a': {1: 11}, 'c': {3: 33, 5: 55}, 
'b': {2: 22}, 'e': {6: 66}, 'd': {4: 44}})
"""

Last edited by vegaseat; Sep 16th, 2009 at 2:25 pm.

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