Change None value in a column to string 'None' in Python

Question

Some columns in my data set have missing values that are represented as None (Nonetype, not a string). Some other missing values are represented as 'N/A' or 'No'. I want to be able to handle these missing values in below method.

df.loc[df.col1.isin('None', 'Yes', 'No'), col1] = 'N/A'

Now my problem is, None is a value not a string and so I can not use none as 'None'. I have read somewhere we can convert that none value to a string 'None'.

Can anyone kindly give me any clue how to go about it ?

Note 1:

Just for clarity of explanation if I run below code:

df.col1.unique()

I get this output:

array([None, 'No', 'Yes'], dtype=object)

Note 2:

I know I can handle missing or None value with isnull() but in this case I need to use .isin() method

Sample dataframe:

f = {'name': ['john', 'tom', None, 'rock', 'dick'], 'DoB': [None, '01/02/2012', '11/22/2014', '11/22/2014', '09/25/2016'], 'Address': ['NY', 'NJ', 'PA', 'NY', None]}
df1 = pd.DataFrame(data = f)

When you run below code you will see None as a value.

df1.Address.unique()
output: array(['NY', 'NJ', 'PA', None], dtype=object)

I want the None to be displayed as 'None'

Can you give an input dataframe and your expected output? I tried answering your question, but am not sure what you actually need. — PdevG
– PdevG, Commented Apr 26, 2018 at 13:35
could you provide more context on why do you want to do this? The export methods (e.g., df.to_csv) have na_rep arguments that can change all of the null/missing data to any string you want. — Paul H
– Paul H, Commented Apr 26, 2018 at 14:08

Bryce Ramgovind · Accepted Answer · 2018-04-26 13:40:28Z

1

There is a different between a null/None and 'None'. So you can change your original statement to

df.loc[df.col1.isin([None, 'Yes', 'No']), col1] = 'N/A'

That is, take out the apostrophes for None

Or you can first find all the indices where a null's or none's exist and then select all those rows based on the index. And then you can use your original statement.

df["col1"].loc[df["col1"].isnull()] = 'None'

edited Apr 26, 2018 at 13:40

answered Apr 26, 2018 at 13:31

Bryce Ramgovind

3,30713 gold badges47 silver badges72 bronze badges

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

Comments

PdevG · Accepted Answer · 2018-04-26 13:32:22Z

0

Create an example df:

df = pd.DataFrame({"A": [None, 'Yes', 'No', 1, 3, 5]})

which looks like:

Replace your 'None' by None and make the to be replaced arguments a list (that's how isin works):

df.loc[df.A.isin([None, 'Yes', 'No']), 'A'] = 'N/A'

which returns:

     A
0  N/A
1  N/A
2  N/A
3    1
4    3
5    5

answered Apr 26, 2018 at 13:32

PdevG

3,6972 gold badges18 silver badges34 bronze badges

Collectives™ on Stack Overflow

Change None value in a column to string 'None' in Python

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related