如何摆放 pandas 数据帧中每行的行值？ [英] How can i pivot down my row values for each row in pandas dataframe?

问题描述

我的数据框架：

    Name  Percent Subject1 Subject2
  ramesh       85    Maths  Science
     ram       42    Maths      
     Raj       85      NaN  Science

输出数据框：

     Name  Percent  Subject
   ramesh       85    Maths
   ramesh       85  Science
      ram       42    Maths
      Raj       85  Science

推荐答案

pd.lreshape 可以将多列的值组合成一个：

pd.lreshape can combine the values from multiple columns into one:

import numpy as np
import pandas as pd
nan = np.nan
df = pd.DataFrame({'Name': ['ramesh', 'ram', 'Raj'],
                   'Percent': [85, 42, 85],
                   'Subject1': ['Maths', 'Maths', nan],
                   'Subject2': ['Science', nan, 'Science']})

print(pd.lreshape(df, {'Subject':['Subject1', 'Subject2']}))

b
$ b

yields

     Name  Percent  Subject
0  ramesh       85    Maths
1     ram       42    Maths
2  ramesh       85  Science
3     Raj       85  Science

---

pd.lreshape 在中似乎没有记录（但是？）在线文档。这是它的docstring：

---

pd.lreshape does not appear to be documented (yet?) in the online docs. Here is its docstring:

In [40]: help(pd.lreshape)
Help on function lreshape in module pandas.core.reshape:

lreshape(data, groups, dropna=True, label=None)
    Reshape long-format data to wide. Generalized inverse of DataFrame.pivot

    Parameters
    ----------
    data : DataFrame
    groups : dict
        {new_name : list_of_columns}
    dropna : boolean, default True

    Examples
    --------
    >>> import pandas as pd
    >>> data = pd.DataFrame({'hr1': [514, 573], 'hr2': [545, 526],
    ...                      'team': ['Red Sox', 'Yankees'],
    ...                      'year1': [2007, 2008], 'year2': [2008, 2008]})
    >>> data
       hr1  hr2     team  year1  year2
    0  514  545  Red Sox   2007   2008
    1  573  526  Yankees   2007   2008

    >>> pd.lreshape(data, {'year': ['year1', 'year2'], 'hr': ['hr1', 'hr2']})
          team   hr  year
    0  Red Sox  514  2007
    1  Yankees  573  2007
    2  Red Sox  545  2008
    3  Yankees  526  2008

    Returns
    -------
    reshaped : DataFrame

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