select rows with null value python-pandas

Question

How can I select the rows with null values in respect of columns name?

What I have:

ID	A	B
1	a	b
2		v
3	y
4	w	j
5	w

What I want:

Select rows with null in respect with e.g. column B:

ID	B
3	y
5	w

Answer 1

Use pandas.DataFrame.pop and pandas.Series.isna:

>>> df
   ID    A    B
0   1    a    b
1   2  NaN    v
2   3    y  NaN
3   4    w    j
4   5    w  NaN

>>> df[df.pop('B').isna()]

   ID  A
2   3  y
4   5  w

Use pop if you do not need column 'B' in the original dataframe afterwards. Otherwise, use pandas.DataFrame.drop:

>>> df[df['B'].isna()].drop('B', axis=1)

Answer 2

I guess you can use isna() or isnull() functions.

df[df['column name'].isna()]

(or)

df[df['column name'].isnull()]