Day 1 2019-05-29 Pandas 的数据结构介绍

Series

Series 是一种类似于一维数组的对象，它由一组数据（各种Numpy 数据类型）以及与之相关的数据标签（即索引）组成。

obj = Series([4,7,-5,3]) 
obj

Out[217]:

0    4

1    7

2   -5

3    3

Series 类同于一个定长的有序字典，其索引值为其映射。Python 字典可直接被用来进行Series 创建。

sdata = {'Ohio':35000,
         'Texas': 71000,
         'Oregon':16000,
         'Utah':5000}

obj3 = Series(sdata)

obj3
Out[232]: 
Ohio      35000
Texas     71000
Oregon    16000
Utah       5000
dtype: int64

states = ['California',
          'Ohio','Oregon',
          'Texas']

obj4 = Series(sdata, index = states)

obj4
Out[240]: 
California        NaN
Ohio          35000.0
Oregon        16000.0
Texas         71000.0
dtype: float64

DataFrame

data = {'state':['Ohio','Ohio','Ohio','Nevada','Nevada'],
        'year':[2000,2001,2002,2001,2002],
        'pop':[1.5,1.7,3.6,2.4,2.9]}

frame = DataFrame(data)

frame
Out[250]: 
    state  year  pop
0    Ohio  2000  1.5
1    Ohio  2001  1.7
2    Ohio  2002  3.6
3  Nevada  2001  2.4
4  Nevada  2002  2.9