Map Values

Remarks#

it should be mentioned that if the key value does not exist then this will raise KeyError, in those situations it maybe better to use merge or get which allows you to specify a default value if the key doesn’t exist

Map from Dictionary

Starting from a dataframe df:

  U   L
111  en
112  en
112  es
113  es
113  ja
113  zh
114  es

Imagine you want to add a new column called S taking values from the following dictionary:

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

You can use map to perform a lookup on keys returning the corresponding values as a new column:

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

that returns:

  U   L   S
111  en  en
112  en  en
112  es  en
113  es  es
113  ja  es
113  zh  es
114  es  es