Add column to pandas.Dataframe using key values from dictionary

Question

I have the below dataframe:

And I have the below dictionary:

resource_ids_dict = {'Austria':1586023272, 'Bulgaria':1550004006, 'Croatia':1131119835, 'Denmark':1703440195, 
                     'Finland':2005848983, 'France':1264698819, 'Germany':1907737079, 'Greece':2113941104, 
                     'Italy':27898245, 'Netherlands':1832579427, 'Norway':1054291604, 'Poland':1188865122, 
                     'Romania':270819662, 'Russia':2132391298, 'Serbia':1155274960, 'South Africa':635838568, 
                     'Spain':52600180, 'Switzerland':842323896, 'Turkey':1716131192, 'UK':199152257}

I am using the above dictionary values to make calls to a vendor API. I then append all the return data into a dataframe df.

What I would like to do now is add a column after ID that is the dictionary keys of the dictionay values that lie in ResourceSetID.

I have had a look on the web, but haven't managed to find anything (probably due to my lack of accurate key word searches). Surely this should be a one-liner? I want avoid looping through the dataframe and the dictionary and mapping that way..

jezrael · Accepted Answer · 2020-08-05 10:35:05Z

5

Use Series.map but first is necessary swap values with keys in dictionary:

d = {v:k for k, v in resource_ids_dict.items()}
#alternative
#d = dict(zip(resource_ids_dict.values(), resource_ids_dict.keys()))
df['new'] = df['ResourceSetID'].map(d)

answered Aug 5, 2020 at 10:35

jezrael

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5 Comments

DDV Over a year ago

Thanks! It is completing the task, but returning this warning:

C:\Users\User\Documents\Anaconda\lib\site-packages\ipykernel_launcher.py:5: SettingWithCopyWarning:  A value is trying to be set on a copy of a slice from a DataFrame. Try using .loc[row_indexer,col_indexer] = value instead  See the caveats in the documentation: http://pandas.pydata.org/pandas-docs/stable/user_guide/indexing.html#returning-a-view-versus-a-copy   """

. Do you know what this means?

jezrael Over a year ago

@Dean - it means DataFrame is created by some filter, need .copy() like this

DDV Over a year ago

Okay, so you make a copy of the dataframe you have filtered instead of changing the original one, per se?

jezrael Over a year ago

@Dean - exactly, you need modify your code before mapping similar way - if still problem, please show me code used before map and I can help you find where is necessary add .copy()

DDV Over a year ago

No, that's perfect. Thanks for explaining. I am still very new to python so most important for me is to get the understanding :) the df was a 'filtered' version of the original dataframe as only need the 3 columns from original 10+. So .copy() works great - thanks again!

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