pandas - add new column to dataframe from dictionary

Question

I would like to add a column 'D' to a dataframe like this:

U,L

111,en

112,en

112,es

113,es

113,ja

113,zh

114,es

based on the following Dictionary:

d = {112: 'en', 113: 'es', 114: 'es', 111: 'en'}

so that the resulting dataframe appears as:

U,L,D

111,en,en

112,en,en

112,es,en

113,es,es

113,ja,es

113,zh,es

114,es,es

So far I tried the pd.join() method but I can't figured out how it works with Dictionaries.

Answer 1

First call map and then pass the dict. It will perform a lookup and return the associated value for that key:

In [248]:

d = {112: 'en', 113: 'es', 114: 'es', 111: 'en'}

df['D'] = df['U'].map(d)

df

Out[248]:

     U   L   D

0  111  en  en

1  112  en  en

2  112  es  en

3  113  es  es

4  113  ja  es

5  113  zh  es

6  114  es  es