pandas ：如何摆脱数据框中的“未命名：”列 [英] Pandas: how to get rid of `Unnamed:` column in a dataframe

问题描述

我有一种情况，有时当我从 df 读取 csv 时，我会得到一个不需要的类索引列名为未命名：0 。这很烦人！我试过了

I have a situation wherein sometimes when I read a csv from df I get an unwanted index-like column named unnamed:0. This is very annoying! I have tried

merge.to_csv('xy.df', mode = 'w', inplace=False)

我认为这是一个解决方案，但我仍然得到未命名：0 专栏！有没有人对此有所了解？

which I thought was a solution to this, but I am still getting the unnamed:0 column! Does anyone have an idea on this?

推荐答案

这是索引列，传递 index = False 不写出来，请参阅 docs

It's the index column, pass index=False to not write it out, see the docs

示例：

In [37]:
df = pd.DataFrame(np.random.randn(5,3), columns=list('abc'))
pd.read_csv(io.StringIO(df.to_csv()))

Out[37]:
   Unnamed: 0         a         b         c
0           0  0.109066 -1.112704 -0.545209
1           1  0.447114  1.525341  0.317252
2           2  0.507495  0.137863  0.886283
3           3  1.452867  1.888363  1.168101
4           4  0.901371 -0.704805  0.088335

与以下项比较：

In [38]:
pd.read_csv(io.StringIO(df.to_csv(index=False)))

Out[38]:
          a         b         c
0  0.109066 -1.112704 -0.545209
1  0.447114  1.525341  0.317252
2  0.507495  0.137863  0.886283
3  1.452867  1.888363  1.168101
4  0.901371 -0.704805  0.088335

你也可以选择通过传递 index_col =告诉 read_csv 第一列是索引列0 ：

You could also optionally tell read_csv that the first column is the index column by passing index_col=0:

In [40]:
pd.read_csv(io.StringIO(df.to_csv()), index_col=0)

Out[40]:
          a         b         c
0  0.109066 -1.112704 -0.545209
1  0.447114  1.525341  0.317252
2  0.507495  0.137863  0.886283
3  1.452867  1.888363  1.168101
4  0.901371 -0.704805  0.088335

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