How to proceed with `None` value in pandas fillna

user_1868738 0
Viewed 43903

I have the following dictionary:

fillna(value={'first_name':'Andrii', 'last_name':'Furmanets', 'created_at':None})

When I pass that dictionary to fillna I see:

raise ValueError('must specify a fill method or value')\nValueError: must specify a fill method or value\n"

It seems to me that it fails on None value.

I use pandas version 0.20.3.

pandas python
5 Answers

In case you want to normalize all of the nulls with python's None.

df.fillna(np.nan).replace([np.nan], [None])

The first fillna will replace all of (None, NAT, np.nan, etc) with Numpy's NaN, then replace Numpy's NaN with python's None.

user_73741990

An alternative method to fillna with None. I am on pandas 0.24.0 and I am doing this to insert NULL values to POSTGRES database.

# Stealing @pIRSquared dataframe
df = pd.DataFrame(dict(A=[1, None], B=[None, 2], C=[None, 'D']))

df

     A    B     C
0  1.0  NaN  None
1  NaN  2.0     D

# fill NaN with None. Basically it says, fill with None whenever you see NULL value.
df['A'] = np.where(df['A'].isnull(), None, df['A'])
df['B'] = np.where(df['B'].isnull(), None, df['B'])

# Result
df

     A    B     C
0  1.0  None  None
1  None  2.0     D
user_73734400

It's a bad idea to try to fill a datetime with None, this is exactly what pandas NaT (NotATime), is for: for missing datetimes.

user_2022290
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