# (1) Count NaN values under a single DataFrame column:
df['column name'].isna().sum()
#(2) Count NaN values under an entire DataFrame:
df.isna().sum().sum()
#(3) Count NaN values across a single DataFrame row:
df.loc[[index value]].isna().sum().sum()
# 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"]), :]
# Count NaN values under a single DataFrame column:
df['column name'].isna().sum()
# Count NaN values under an entire DataFrame:
df.isna().sum().sum()
# Count NaN values across a single DataFrame row:
df.loc[[index value]].isna().sum().sum()