How to Select Rows with One or More Nulls from a Pandas Dataframe Without Listing Columns Explicitly

Display rows with one or more NaN values in pandas dataframe

You can use DataFrame.any with parameter axis=1 for check at least one True in row by DataFrame.isna with boolean indexing:

df1 = df[df.isna().any(axis=1)]

d = {'filename': ['M66_MI_NSRh35d32kpoints.dat', 'F71_sMI_DMRI51d.dat', 'F62_sMI_St22d7.dat', 'F41_Car_HOC498d.dat', 'F78_MI_547d.dat'], 'alpha1': [0.8016, 0.0, 1.721, 1.167, 1.897], 'alpha2': [0.9283, 0.0, 3.833, 2.809, 5.459], 'gamma1': [1.0, np.nan, 0.23748000000000002, 0.36419, 0.095319], 'gamma2': [0.074804, 0.0, 0.15, 0.3, np.nan], 'chi2min': [39.855990000000006, 1e+25, 10.91832, 7.966335000000001, 25.93468]}
df = pd.DataFrame(d).set_index('filename')

print (df)
                             alpha1  alpha2    gamma1    gamma2       chi2min
filename                                                                     
M66_MI_NSRh35d32kpoints.dat  0.8016  0.9283  1.000000  0.074804  3.985599e+01
F71_sMI_DMRI51d.dat          0.0000  0.0000       NaN  0.000000  1.000000e+25
F62_sMI_St22d7.dat           1.7210  3.8330  0.237480  0.150000  1.091832e+01
F41_Car_HOC498d.dat          1.1670  2.8090  0.364190  0.300000  7.966335e+00
F78_MI_547d.dat              1.8970  5.4590  0.095319       NaN  2.593468e+01

Explanation:

print (df.isna())
                            alpha1 alpha2 gamma1 gamma2 chi2min
filename                                                       
M66_MI_NSRh35d32kpoints.dat  False  False  False  False   False
F71_sMI_DMRI51d.dat          False  False   True  False   False
F62_sMI_St22d7.dat           False  False  False  False   False
F41_Car_HOC498d.dat          False  False  False  False   False
F78_MI_547d.dat              False  False  False   True   False

print (df.isna().any(axis=1))
filename
M66_MI_NSRh35d32kpoints.dat    False
F71_sMI_DMRI51d.dat             True
F62_sMI_St22d7.dat             False
F41_Car_HOC498d.dat            False
F78_MI_547d.dat                 True
dtype: bool

df1 = df[df.isna().any(axis=1)]
print (df1)
                     alpha1  alpha2    gamma1  gamma2       chi2min
filename                                                           
F71_sMI_DMRI51d.dat   0.000   0.000       NaN     0.0  1.000000e+25
F78_MI_547d.dat       1.897   5.459  0.095319     NaN  2.593468e+01

Select rows of a dataframe where at least one column is NaN

Use isnull with any

df[df.isnull().any(1)]
Out[122]: 
   columnA  columnB
0      NaN      1.0
2      NaN      NaN
3      1.0      NaN

filter dataframe using isna() to filter ourt rows that have null value in following columns

You can filter if exist at least one non missing values after second columns with DataFrame.notna and DataFrame.any:

df = df[df.iloc[:,2:].notna().any(axis=1)]
print (df)
     id  name  val1_rain  val2_tik  val3_bon  val4_tig
0  2349  Rivi       0.11      0.34      0.78      0.21
2   835  Pigi       0.34       NaN      0.32       NaN
3  5093  Tari       0.65      0.12      0.34      2.45

Select data when specific columns have null value in pandas

Use boolean indexing:

mask = df['Date1'].isnull() | df['Date2'].isnull()
print (df[mask])
           ID     Date1     Date2
0  58844880.0  04/11/16       NaN
2  59743311.0  04/13/16       NaN
4  59598413.0       NaN       NaN
8  59561198.0       NaN  04/17/16

Timings:

#[900000 rows x 3 columns]
df = pd.concat([df]*100000).reset_index(drop=True)

In [12]: %timeit (df[df['Date1'].isnull() | df['Date2'].isnull()])
10 loops, best of 3: 89.3 ms per loop

In [13]: %timeit (df[df.filter(like='Date').isnull().any(1)])
10 loops, best of 3: 146 ms per loop

select rows based on a combination of strings without order in strings

Might as well just make separate masks for both words in this case. If you have a longer list of words, there are better solutions.

df_ = df_[df_['summary'].str.contains('slow') & df_['summary'].str.contains('delivery')]