How to add a column with values of a dictionary in Python

user_7472392 0
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I am trying to add a column with values from a dictionary. It will be easy to show you the dummy data.

df = pd.DataFrame({'id':[1,2,3,2,5], 'grade':[5,2,2,1,3]})

dictionary = {'1':[5,8,6,3], '2':[1,2], '5':[8,6,2]}

Notice that not every id is in the dictionary and the values which are the lists. I want to find the row in the df that matches with the keys in the dictionary and add the list in one column. So the desired output will look like this:

output = pd.DataFrame({'id':[1,2,3,2,5], 'grade':[5,2,2,1,3], 'new_column':[[5,8,6,3],[1,2],[],[1,2],[8,6,2]]})
pandas dataframe dictionary python
3 Answers

Is this what you want?

df = df.set_index('id')
dictionary = {1:[5,8,6,3], 2:[1,2], 5:[8,6,2]}    
df['new_column'] = pd.Series(dictionary)

Note: The keys of the dictionary need to be the same type (int) as the index of the data frame.

>>> print(df)
    gender    new_column
id                      
1        0  [5, 8, 6, 3]
2        0        [1, 2]
3        1           NaN
4        1           NaN
5        1     [8, 6, 2]

Update:

A better solution if 'id' column contains duplicates (see comments below):

df['new_column'] = df['id'].map(dictionary)
user_16095140 
import pandas as pd

df = pd.DataFrame({'id':[1,2,3,4,5], 'gender':[0,0,1,1,1]})

dictionary = {'1':[5,8,6,3], '2':[1,2], '5':[8,6,2]}

then just create a list with the values you want and add them to your dataframe

newValues = [ dictionary.get(str(val),[]) for val in df['id'].values]

df['new_column'] = newValues


>>> print(df)
    gender    new_column
id                      
1        0  [5, 8, 6, 3]
2        0        [1, 2]
3        1            []
4        1            []
5        1     [8, 6, 2]
user_99838800

You can construct your column using special dictionaries that has a value [] by default.

from collections import defaultdict
default_dictionary = defaultdict(list)
id = [1,2,3,4,5]
dictionary = {'1':[5,8,6,3], '2':[1,2], '5':[8,6,2]}
for n in dictionary:
    default_dictionary[n] = dictionary[n]
new_column = [default_dictionary[str(n)] for n in id]

new_column is [[5, 8, 6, 3], [1, 2], [], [], [8, 6, 2]] now and you can pass it to your last argument of pd.DataFrame(...)

user_30448250
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