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Description
- I have checked that this issue has not already been reported.
- I have confirmed this bug exists on the latest version of pandas (1.0.5)
series = pd.Series({'1':1,'2':None,'3':np.nan, '4':''})
will create a series which looks like:
1 1
2 None
3 NaN
4
dtype: object
When using the fillna method on this series on index 3 it changes also the entry in index 2!
series.fillna({'3':0})
This will result in a output as follows:
1 1
2 NaN
3 0
4
dtype: object
Problem:
The value at index 2 changed from None to NaN.
Expected Behaviour:
The value at index 2 should never be touched when using fillna and specifying the indices you want to alter.