How to add values from one dictionary to another based on matching keys?

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I have two dictionaries with matching keys and different values. I want to add the values of a to b.

Some keys are in dictionary a but not b. I want to skip over these.

a = {1:"a", 2:"b", 3:"c", 4:"d"}
b = {1:"e", 2:"f", 3:"g"}



for k, v in a.items():
    if k in b.keys():
        list(b).append(v)
    else: print 'Could not locate key', k

I would like the output to be b = {1: ["e", "a"], 2: ["b", "f"], 3: ["g","c"]}

Instead the values aren't appending. I've also tried using brackets around the v, which returns

TypeError: 'builtin_function_or_method' object has no attribute '__getitem__'

Is this something that you want?

a = {1:"a", 2:"b", 3:"c", 4:"d"}
b = {1:"e", 2:"f", 3:"g"}
c={}

keys = set(list(a.keys())+list(b.keys()))

for key in keys:
    items = []
    items += [a[key]] if key in a else []
    items += [b[key]] if key in b else []
    c[key]=items

Python, Python | Combine two dictionary adding values for common keys. Given two dictionary, the task is to combine the dictionaries such that we get the added values for common keys in resultant dictionary. Method #1: Naive method See your article appearing on the GeeksforGeeks main page and help other Geeks. Append multiple key value pair in dictionary As update () accepts an iterable sequence of key value pairs, so we can pass a dictionary or list of tuples of new key value pairs to update (). It will all add the given key value pairs in the dictionary, if any key already exists then it will update its value.


I think this is what you want... I used strings for the original values but will still work with lists.

>>> a = {"1":"a", "2":"b", "3": "c", "4":"d"}
>>> b = {"1":"e", "2":"f", "3":"g"}
>>> for k, v in a.items():
...     if k in b:
...         b[k] = [a[k], b[k]]
... 
>>> b
{'1': ['a', 'e'], '2': ['b', 'f'], '3': ['c', 'g']}

Associating Multiple Values with Each Key in a Dictionary, You need a dictionary that maps each key to multiple values. not hard to make it one-to-many—in other words, to make one key map to multiple values. approaches, depending on how you want to treat duplications in the set of values for a key. Of course, you need to be able to do more than just add values for a key. This function iterate over all the key value pairs in dictionary and call the given callback function () on each pair. Items for which callback () function returns True are added to the new dictionary. In the end new dictionary is returned. Now let’s use this to filter a dictionary by key i.e.


    a = {1:"a", 2:"b", 3:"c", 4:"d"}
    b = {1:"e", 2:"f", 3:"g"}

    for k, v in a.items():
        if k in b.keys():
            b[k] = [v,b[k]]
        else: print('Could not locate key', k)
    print(b)

output :
Could not locate key 4
{1: ['a', 'e'], 2: ['b', 'f'], 3: ['c', 'g']}

use b[k] = [v,b[k]] instead of list(b).append(v)

list(b).append(v) means you are creating a list of keys of dictionary b and then appending v to that

b[k] = [v,b[k]] means create a list of values of dict a and b for key k and assign to dictionary b at key k

Dictionary Data Structures in Python 3, Dictionaries map keys to values, making key-value pairs that can then store data. the key-value pairs will remain intact, enabling us to access data based on their relational In this section, we'll go over adding and deleting dictionary elements. In this case, we'll reference an existing key and pass a different value to it. I have a dictionary with a list of values of varying numbers of items. I want to compare the values of this dictionary (dict1) to the keys of another (dict2), and if they match print the key and value of the matching component of dict1, along with the value of dict2.


Python: Match key values in two dictionaries, Write a Python program to match key values in two dictionaries. Sample Solution: Python Code: x = {'key1': 1, 'key2': 3, 'key3': 2} y = {'key1': 1, 'key2': 2} for (key, value) in Write a Python program to replace dictionary values with their sum. You can use a global variable in other functions by declaring it as  Now we have a dataframe of top 5 countries and their population and a dictionary which holds the country as Key and their National Capitals as value pair. Let’s create a new column called capital in the dataframe matching the Key value pair from the country column. Create Column Capital matching Dictionary value


dict manual page - Tcl Built-In Commands, Performs one of several operations on dictionary values or variables containing dictionary values (see the dict append dictionaryVariable key ?string . Method #2 : Using next() + dictionary comprehension The combination of these methods can also be used to perform this task. This difference is that it’s a one liner and more efficient as next function uses iterator as internal implementation which are quicker than generic methods.


Python Dictionary(Dict): Update, Cmp, Len, Sort, Copy, Items, str , Python Dictionary are defined into two elements Keys and Values. Keys will be a single element; Values can be a list or list within a list, numbers, etc. In this Here in the example we will add another name "Sarah" to our existing dictionary. SciPy is an Open Source Python-based library, which is used in  Python | Add new keys to a dictionary Dictionary in Python is an unordered collection of data values, used to store data values like a map, which unlike other Data Types that hold only single value as an element, Dictionary holds key:value pair.