Pandas 系列仅将 NaN 填充到一定限度

Question

I have a dataset "artwork.csv" https://gitlab.com/IEA_ML_LAB/test/-/blob/80713d4823c4778d11468bcaf4a5223f6a160c88/artwork.csv

The 'year' column includes int64 and NaN.

I want to replace the first 100 NaN values with text 'no date'. I tried different methods but didn't succeed.

'year' columns has 1279 NaN values. I want to set the first 100 out of 1279 to 'no date'

The first 100 NaN values:

I try the below commands. They don't produce any errors but they don't modify the Series either:

df.loc[df.year.isnull(), 'year'].iloc[:100] = 'no date'

(df.loc[df.year.isnull(), 'year'].iloc[:100]).replace('NaN', 'no date', inplace=True)

(df.loc[df.year.isnull(), 'year'].iloc[:100]).transform(lambda x: 'no date')

Thanks in advance.

Answer 1

fillna has a limit argument you can set to 100:

df['year'] = df['year'].fillna('no date', limit=100)

No need to call iloc beforehand, as that would generate an additional copy of data.

Although beware mixing strings and floats is probably not the best option here as it severely impacts performance while handling the data.