Pandas: print column name with missing values

Question

I am trying to print or to get list of columns name with missing values. E.g.

data1 data2 data3   1     3     3   2     NaN   5   3     4     NaN   

I want to get ['data2', 'data3']. I wrote following code:

print('\n'.join(map(     lambda x : str(x[1])     ,(filter(lambda z: z[0] != False, zip(train.isnull().any(axis=0), train.columns.values))) ))) 

It works well, but I think should be simpler way.

Answer 1

df.isnull().any() generates a boolean array (True if the column has a missing value, False otherwise). You can use it to index into df.columns:

df.columns[df.isnull().any()] 

will return a list of the columns which have missing values.

---

df = pd.DataFrame({'A': [1, 2, 3],                     'B': [1, 2, np.nan],                     'C': [4, 5, 6],                     'D': [np.nan, np.nan, np.nan]})  df Out:     A    B  C   D 0  1  1.0  4 NaN 1  2  2.0  5 NaN 2  3  NaN  6 NaN  df.columns[df.isnull().any()] Out: Index(['B', 'D'], dtype='object')  df.columns[df.isnull().any()].tolist()  # to get a list instead of an Index object Out: ['B', 'D'] 

Answer 2

Oneliner -

[col for col in df.columns if df[col].isnull().any()]