python-3.x - pandas pivot 转换 DataFrame

Question

我只是想玩 will pivot 以我希望的方式转换数据帧，但这里不起作用。

请任何专家见解。

数据框:

>>> df1
     id   item value
0  2225  prize   1.5
1  2225   unit    kg
2  2225  prize   2.4
3  8187   unit    lt
4  1401  stock    10
5  1401  prize   4.3

在运行 pivot 时我看到以下错误..

>>> df1.pivot('id', 'item')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/grid/common/pkgs/python/v3.6.1/lib/python3.6/site-packages/pandas/core/frame.py", line 4359, in pivot
    return pivot(self, index=index, columns=columns, values=values)
  File "/grid/common/pkgs/python/v3.6.1/lib/python3.6/site-packages/pandas/core/reshape/reshape.py", line 381, in pivot
    return indexed.unstack(columns)
  File "/grid/common/pkgs/python/v3.6.1/lib/python3.6/site-packages/pandas/core/frame.py", line 4546, in unstack
    return unstack(self, level, fill_value)
  File "/grid/common/pkgs/python/v3.6.1/lib/python3.6/site-packages/pandas/core/reshape/reshape.py", line 469, in unstack
    return _unstack_frame(obj, level, fill_value=fill_value)
  File "/grid/common/pkgs/python/v3.6.1/lib/python3.6/site-packages/pandas/core/reshape/reshape.py", line 488, in _unstack_frame
    fill_value=fill_value)
  File "/grid/common/pkgs/python/v3.6.1/lib/python3.6/site-packages/pandas/core/reshape/reshape.py", line 116, in __init__
    self._make_selectors()
  File "/grid/common/pkgs/python/v3.6.1/lib/python3.6/site-packages/pandas/core/reshape/reshape.py", line 154, in _make_selectors
    raise ValueError('Index contains duplicate entries, '
ValueError: Index contains duplicate entries, cannot reshape

甚至 pivot_table 也会产生错误..

>>> df1.pivot_table(columns='item', values='value')

我试过 github link reference但没有得到它。

想要的应该是这样的:

      Value

item  prize  stock  unit
    id

2225  1.5  10  2.4  lt

Answer 1

您应该尝试以下操作:

pd.pivot_table(df1, values='value', index=['id'], columns=['item'], aggfunc=np.sum)

正如 jezrael 在下面提到的，aggfunc 可以表示数值，也可以表示字符串。