I am new to python. please help me how I should proceed. The following dataframe contains large blocks of NaNs. # Fill the NAs with mean only for 2 or less consecutive values of NAs. # Refer to the documentation of fillna() to find out the parameter you would use to fill only a certail number of NAs. # The resulting dataframe should look like df_filled

# The resulting dataframe should look like df_filled shown below.df = pd.DataFrame({'val1':[4,np.nan,7,np.nan,np.nan,9,5, np.nan , 1,9,np.nan, np.nan,np.nan, 5, np.nan], 'val2': [ np.nan, 5,7,np.nan, np.nan,8,3,np.nan, 4,np.nan, np.nan, np.nan,np.nan,21,np.nan]})d = {'val1': {0: 4.0,1: 5.7142857142857144,2: 7.0,3: 5.7142857142857144,4: np.nan,5: 9.0,6: 5.0,7: np.nan,8: 1.0,9: 9.0,10: np.nan,11: np.nan,12: np.nan,13: 5.0,14: np.nan},
'val2': {0: 8.0,1: 5.0,2: 7.0,3: 8.0,4: np.nan,5: 8.0,6: 3.0,7: np.nan,8: 4.0,9: np.nan,10: np.nan,11: np.nan,12: np.nan,13: 21.0,14: np.nan}}df_filled = pd.DataFrame(d)

Let's try this

df["val1"] = df["val1"].transform(lambda x: x.fillna(x.mean(), limit=2))
df["val2"] = df["val2"].transform(lambda x: x.fillna(x.mean(), limit=2))
print df

Don't forget to let us know if it solved your problem :)