pandas引入約定:
import pandas as pd
from pandas import Series
Series是一種類似於一維數組的對象,它由一組數據以及相對應的索引組成。
Series數據可由下面幾種方式生成(索引在左邊,值在右邊):
一、自動創建並生成索引,索引從0開始
In :
import pandas as pd
from pandas import Series
import numpy as np
obj = Series([1,2,3,4])
obj
Out:
二,自定義索引
In :
obj = Series([1,2,3,4],index = ['a', 'b', 'c', 'd'])
obj
Out:三、通過字典創建
1.只傳入一個字典,索引即爲dict的key。
In:
sdata = {'a': 1, 'b': 2, 'c': 3, 'd': 4}
obj = Series(sdata)
obj
Out:
In:
skey = ['a', 'b', 'c', 'd', 'e', 'f']
obj = Series(sdata, skey)
obj
Out:
Series索引可根據賦值立即修改,索引個數要保持一致:
In:
obj.index = ['q', 'w', 'e', 'r', 't', 'y']
obj
Out:
Series可通過索引獲取單個或一組值;可通過索引直接賦值:
In :
obj['a']
Out:In :
obj['a'] = 5
Out:
obj
Series數組運算(如根據布爾型數組進行過濾、標量乘法、應用數學函數等)也會保留索引和值之間的鏈接:
In :
obj[obj > 2]
Out:
a 5
In:
obj *2
Out:
In :
np.exp(obj)
Out:
Series重要功能:在算術運算中會自動對齊不同索引的數據:
In:
sdata = {'a': 1, 'b': 2}
obj1 = Series(sdata, index = ['a', 'b', 'c'])
obj1
Out:
In:
sdata = {'b':2, 'c': 3, 'd':4}
obj2 = Series(sdata)
obj2
Out:
In:
obj1 + obj2
Out: