如何将一个数据帧转换为另一个数据帧？

Question

主席()

    critic  title   rating
0   Jack Matthews   Lady in the Water   3.0
1   Jack Matthews   Snakes on a Plane   4.0
2   Jack Matthews   You Me and Dupree   3.5
3   Jack Matthews   Superman Returns    5.0
4   Jack Matthews   The Night Listener  3.0

我想让它看起来像

critic  Just My Luck    Lady in the Water   Snakes on a Plane   Superman Returns    The Night Listener  You Me and Dupree

Claudia Puig    3.0 NaN 3.5 4.0 4.5 2.5
Gene Seymour    1.5 3.0 3.5 5.0 3.0 3.5
Jack Matthews   NaN 3.0 4.0 5.0 3.0 3.5
Lisa Rose   3.0 2.5 3.5 3.5 3.0 2.5
Mick LaSalle    2.0 3.0 4.0 3.0 3.0 2.0
Toby    NaN NaN 4.5 4.0 NaN 1.0

我试着使用

movie_rating= ratings.pivot(index='critic', columns='title',values='rating')

但它会创建额外的列名。像

title   Just My Luck    Lady in the Water   Snakes on a Plane   Superman Returns    The Night Listener  You Me and Dupree
critic                      
Claudia Puig    3.0 NaN 3.5 4.0 4.5 2.5
Gene Seymour    1.5 3.0 3.5 5.0 3.0 3.5
Jack Matthews   NaN 3.0 4.0 5.0 3.0 3.5
Lisa Rose   3.0 2.5 3.5 3.5 3.0 2.5
Mick LaSalle    2.0 3.0 4.0 3.0 3.0 2.0
Toby    NaN NaN 4.5 4.0 NaN 1.0

Answer 1

您看到的不是额外的列。这些是行和列的索引名称。行索引名为'critic'，列索引名为'title'。要使数据透视框显示时不带它们，只需将name参数设置为None以表示index和columns

import pandas as pd

df = pd.DataFrame({'critic':list('AABBCC'), 
                   'title':['hello','world']*3, 
                   'rating':[4,3,6,2,3,2]}

p = df.pivot(index='critic', columns='title',values='rating')
p
# returns:
title   hello  world
critic
A           4      3
B           6      2
C           3      2

您可以看到title和critic分别是columns和index的名称属性

p.columns, p.index
# returns:
(Index(['hello', 'world'], dtype='object', name='title'),
 Index(['A', 'B', 'C'], dtype='object', name='critic'))

要删除显示的名称，只需覆盖index和columns对象的name属性即可

p.index.name = None
p.columns.name = None
p
# returns:
   hello  world
A      4      3
B      6      2
C      3      2