python – ValueError:长度不匹配:在pandas数据帧中创建分层列
发布时间:2020-12-20 11:59:10 所属栏目:Python 来源:网络整理
导读:我正在阅读关于Pandas中的层次索引的 documentation.我尝试从中测试示例以创建带有分层索引的空数据框: In [5]: df = pd.DataFrame()In [6]: df.columns = pd.MultiIndex(levels = [['first','second'],['a','b']],labels = [[0,1,1],[0,1]]) 但是,它会抛出
我正在阅读关于Pandas中的层次索引的
documentation.我尝试从中测试示例以创建带有分层索引的空数据框:
In [5]: df = pd.DataFrame() In [6]: df.columns = pd.MultiIndex(levels = [['first','second'],['a','b']],labels = [[0,1,1],[0,1]]) 但是,它会抛出一个错误: ValueError Traceback (most recent call last) <ipython-input-6-dd823f9b8d22> in <module>() ----> 1 df.columns = pd.MultiIndex(levels = [['first',1]]) /usr/local/lib/python3.4/dist-packages/pandas/core/generic.py in __setattr__(self,name,value) 2755 try: 2756 object.__getattribute__(self,name) -> 2757 return object.__setattr__(self,value) 2758 except AttributeError: 2759 pass pandas/src/properties.pyx in pandas.lib.AxisProperty.__set__ (pandas/lib.c:44873)() /usr/local/lib/python3.4/dist-packages/pandas/core/generic.py in _set_axis(self,axis,labels) 446 447 def _set_axis(self,labels): --> 448 self._data.set_axis(axis,labels) 449 self._clear_item_cache() 450 /usr/local/lib/python3.4/dist-packages/pandas/core/internals.py in set_axis(self,new_labels) 2800 raise ValueError('Length mismatch: Expected axis has %d elements,' 2801 'new values have %d elements' % -> 2802 (old_len,new_len)) 2803 2804 self.axes[axis] = new_labels ValueError: Length mismatch: Expected axis has 0 elements,new values have 4 elements 我没有看到我的代码有任何问题.有什么想法发生了什么? 解决方法
问题是你有一个空数据框,它有零列,你试图为它分配一个四列多索引;如果最初创建一个包含四列的空数据框,则错误将消失:
df = pd.DataFrame(pd.np.empty((0,4))) df.columns = pd.MultiIndex(levels = [['first',1]]) 或者您可以使用多索引创建空数据框,如下所示: multi_index = pd.MultiIndex(levels = [['first',1]]) df = pd.DataFrame(columns=multi_index) df # first second # a b a b (编辑:李大同) 【声明】本站内容均来自网络,其相关言论仅代表作者个人观点,不代表本站立场。若无意侵犯到您的权利,请及时与联系站长删除相关内容! |