Add a new column to pandas data frame from dictionary

Question

I want to add a new column to my dataframe and map it to a dictionary. Mapping should be on the index of my original dataframe and I don't know how to use .map() to get there.

d={'KO': 'Consumer, Non-cyclical', 'AAPL': 'Technology'}

df:

Date   2015-12-01   
KO    2144.499950  
AAPL  5162.959824

I would like the result too look like this:

df:

Date   2015-12-01  industry 
KO    2144.499950  Consumer, Non-cyclical
AAPL  5162.959824  Technology

Andy Hayden · Accepted Answer · 2015-12-12 04:13:02Z

4

Construct the Series first:

df["industry"] = pd.Series(d)

Note: This assumes that the dict keys are in the DataFrame index:

In [11]: df
Out[11]:
       2015-12-01
KO    2144.499950
AAPL  5162.959824

In [12]: df["industry"] = pd.Series(d)

In [13]: df
Out[13]:
       2015-12-01                industry
KO    2144.499950  Consumer, Non-cyclical
AAPL  5162.959824              Technology

answered Dec 12, 2015 at 4:13

Andy Hayden

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3 Comments

vol_of_vol Over a year ago

Thanks Andy. This is good. I was about to reindex the df data frame and have it indexed with 0,1,2,3, ... . Then move KO, AAPL,.. to fist column and use map() afterwards.

Mugen Over a year ago

A very basic question. What does the code In[11] and Out[11] mean?\

Andy Hayden Over a year ago

@Mugen it's ipython/jupyter syntax. highly recommended download. e.g. see ipython.readthedocs.io/en/stable/interactive/tutorial.html

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