NaN

np.nan

任何與NaN都是NaN
1+NaN=NaN
1*NaN=NaN

NaN in Series

s1=Series([1,2,np.nan,np.nan],index=[‘A’,’B’,’C’,’D’])
s1.isnull()
s1.notnull()
s1.dropna()

NaN in DataFrame

df=DataFrame([[1,2,3],[4,np.nan,6],[7,np,nan,9]])#crate dataframe by list
df.isnull()
df.notnull()
df.dropna()
df.drop(axis=1)#NaN drop column
df.dropna(how=’any’)#NaN drop row
df.dropna(how=’all’)#全部NaN才會drop row
df.dropna(axis=1,how=’all’)

df.fillna()