Python Question
How to fill pandas dataframe columns with random dictionary values
I'm new to Pandas and I would like to play with random text data. I am trying to add 2 new columns to a DataFrame df which would be each filled by a key (newcol1) + value (newcol2) randomly selected from a dictionary.
countries = {'Africa':'Ghana','Europe':'France','Europe':'Greece','Asia':'Vietnam','Europe':'Lithuania'}
My df already has 2 columns and I'd like something like this :
Year Approved Continent Country
0 2016 Yes Africa Ghana
1 2016 Yes Europe Lithuania
2 2017 No Europe Greece
I can certainly use a for or while loop to fill df['Continent'] and df['Country'] but I sense .apply() and np.random.choice may provide a simpler more pandorable solution for that.
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Answer Source
Yep, you're right. You can use np.random.choice + map:
df
Year Approved
0 2016 Yes
1 2016 Yes
2 2017 No
df['Continent'] = np.random.choice(list(countries), len(df))
df['Country'] = df['Continent'].map(countries)
df
Year Approved Continent Country
0 2016 Yes Africa Ghana
1 2016 Yes Asia Vietnam
2 2017 No Europe Lithuania
You choose len(df) number of keys at random from the country key-list, and then use the country dictionary as a mapper to find the country equivalents of the previously picked keys.
For the second step of replacement, pd.Series.replace also works:
df['Country'] = df.Continent.replace(countries)
df
Year Approved Continent Country
0 2016 Yes Africa Ghana
1 2016 Yes Asia Vietnam
2 2017 No Europe Lithuania
For the sake of completeness, you can also use apply + dict.get:
df['Country'] = df.Continent.apply(countries.get)
df
Year Approved Continent Country
0 2016 Yes Africa Ghana
1 2016 Yes Asia Vietnam
2 2017 No Europe Lithuania
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