Handling Missing Data
Missing values appear as NaN. isna() marks them, fillna(value) replaces them and dropna() removes the rows that have them. Always decide on purpose: dropping loses rows, filling invents numbers.
Examplepython
Quick check
What does `dropna()` do?
Your turn: write the code
Print how many scores are missing (use isna().sum()).
Finish the quick check (and any code exercise) to complete this lesson, or mark it done yourself.
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