接續上次的話題,如果指定一系列的欄 (column),DataFrame 的欄將按照那個順序來排列:
In [53]: pd.DataFrame(data, columns=["year", "state", "pop"])
Out[53]:
year state pop
0 2000 Ohio 1.5
1 2001 Ohio 1.7
2 2002 Ohio 3.6
3 2001 Nevada 2.4
4 2002 Nevada 2.9
5 2003 Nevada 3.2
如果傳入一個在字典找不到的欄,在結果裡會被顯示為缺失值:
In [54]: frame2 = pd.DataFrame(data, columns=["year", "state", "pop", "debt"])
Out[55]: frame2
year state pop debt
0 2000 Ohio 1.5 NaN
1 2001 Ohio 1.7 NaN
2 2002 Ohio 3.6 NaN
3 2001 Nevada 2.4 NaN
4 2002 Nevada 2.9 NaN
5 2003 Nevada 3.2 NaN
In[56]: frame2.columns
Out[56]: Index(['year', 'state', 'pop', 'debt'], dtype ='object')
使用類似字典的語法或屬性語法來取出 DataFrame 的一欄,結果會是 Series 的形式:
In [57]: frame2["state"]
Out[57]: frame2
0 Ohio
1 Ohio
2 Ohio
3 Nevada
4 Nevada
5 Nevada
Name: state, dtype: object
In [58]: frame2.year
Out[58]: frame2
0 2000
1 2001
2 2002
3 2001
4 2002
5 2003
Name: year, dtype: int64
今日的分享就到這囉,我們明天見,掰掰!