Python与数据科学实战课程——第三章Pandas：谈一谈NaN

import numpy as np
import pandas as pd
from pandas import Series,DataFrame

n = np.nan
n

nan

type(n)

float

任何数据类型 不管是int还是float 和nan做运算后得到的结果都是nan

m = 1
m + n            

nan

NaN in series

s1 = Series([1,2,np.nan,3,4],index=["A","B","C","D","E"])
s1

A 1.0
B 2.0
C NaN
D 3.0
E 4.0
dtype: float64

s1.isnull()

A False
B False
C True
D False
E False
dtype: bool

s1.notnull()

A True
B True
C False
D True
E True
dtype: bool

s1.dropna()   #将原有的nan行删除掉

A 1.0
B 2.0
D 3.0
E 4.0
dtype: float64

NaN in DataFrame

dframe = DataFrame