Answers for "dataframe becomes nan when index is given python"

find position of nan pandas

# position of NaN values in terms of index
df.loc[pandas.isna(df["b"]), :].index

# position of NaN values in terms of rows that cotnain NaN
df.loc[pandas.isna(df["b"]), :]

find nan value in dataframe python

# to mark NaN column as True
df['your column name'].isnull()