How to replace multiple values in a pandas dataframe?

Question

How can I replace multiple values with a mapping in a Pandas DataFrame?

I have one column that I want to replace with the following mapping.

mapping
apple=fruit
tomato=vegetable
steak=protein
milk=dairy

So that my column becomes.

col1       ->     col1
apple             fruit
apple             fruit
tomato            vegtable
steak             protein
milk              dairy

How can I do this most efficiently?

miradulo · Accepted Answer · 2017-07-28 00:50:20Z

2

Just create a dictionary with your mapping and then call Series.map.

>>> d = {'apple': 'fruit', 
         'tomato': 'vegetable', 
         'steak': 'protein', 
         'milk': 'dairy'}

>>> df.col1.map(d)

0        fruit
1        fruit
2    vegetable
3      protein
4        dairy
Name: col1, dtype: object

answered Jul 28, 2017 at 0:50

miradulo

29.8k7 gold badges86 silver badges97 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

OptimusPrime Over a year ago

I tired using the code df[col1]=df.col1.map(d) and i got an error. 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

miradulo Over a year ago

@OptimusPrime This is because of a step you must be taking before. Probably subsetting the columns of your DataFrame, doing something like df = df[['col1', 'col2']]. Use df.loc or df.iloc when subsetting columns instead, so that when you go to set a column like this you won't run into problems.

OptimusPrime Over a year ago

can you give me an example? of using loc or iloc? thanks

Collectives™ on Stack Overflow

How to replace multiple values in a pandas dataframe?

1 Answer 1

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related