学习Pandas，第 5 课

英文原文: 05 - Lesson

我们将快速地看一下 stack 和 unstack 这两个函数。

# 导入库
import pandas as pd
import sys

print('Python version ' + sys.version)
print('Pandas version: ' + pd.__version__)

Python version 3.6.1 | packaged by conda-forge | (default, Mar 23 2017, 21:57:00) 
[GCC 4.2.1 Compatible Apple LLVM 6.1.0 (clang-602.0.53)]
Pandas version: 0.19.2

# 我们的小数聚集
d = {'one':[1,1],'two':[2,2]}
i = ['a','b']

# 创建一个 dataframe
df = pd.DataFrame(data = d, index = i)
df

df.index

Index(['a', 'b'], dtype='object')

# 把列(column)放置到索引位置
stack = df.stack()
stack

a  one    1
   two    2
b  one    1
   two    2
dtype: int64

# 现在索引包含了原来的列名字
stack.index

MultiIndex(levels=[['a', 'b'], ['one', 'two']],
           labels=[[0, 0, 1, 1], [0, 1, 0, 1]])

unstack = df.unstack()
unstack

one  a    1
     b    1
two  a    2
     b    2
dtype: int64

unstack.index

MultiIndex(levels=[['one', 'two'], ['a', 'b']],
           labels=[[0, 0, 1, 1], [0, 1, 0, 1]])

用 T (转置)，我们可以把列和索引交换位置。

transpose = df.T
transpose

transpose.index

Index(['one', 'two'], dtype='object')

This tutorial was created by HEDARO

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