Python DataFrame: How to replace Nan with value on one specific position

Question

I am trying to replace NA value at a specific position with another value using pd.DataFrame.fillna(previous_value, value, inplace = True). Although it's no error showing up in the running process, the original Na value hasn't been replaced yet.
Data[pd.isnull(Data["gender"])]

Data Output:

Replace Code:
 Data.loc[[2956]]["gender"].replace(np.nan, "F",inplace = True)

Data after replacement
Data.loc[[2956]]

Dataset after replacement:

Any idea how it happened?

Pranjal dubey · Answer

One method you can try is without using replace. When you know the
index just assign the value you want  Code:

Data.gender[2956]='F'

NANDHA KUMAR · Answer

Try this
    Data.loc[[2956]]["gender"].replace(None, "F",inplace = True)

Guil23 · Answer

Dataframe.replace isn't meant to replace a value at a single position to begin with, but to replace all the values that correspond to something. So in your example, by using replace the best result you could have is having 'Scout Schultz' and 'Tk Tk' 's genders set to 'F'.
Since you know that the row 2956 has NaN in 'gender' column, you can do something like
data.loc[2956, 'gender'] = 'F'

Murilo Malek · Answer

When you get the value using column and row, you take the value, not that position in the dataframe. And you can't use replace() for a single value.
You can just change the value using:
 Data["gender"].loc[[2956]] = 'F'

rhug123 · Answer

You could just do this.
df.loc[2956,'gender'] = 'F'

Python DataFrame: How to replace Nan with value on one specific position

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