Question

我的问题是如何使用DataFrame的append（）方法将行干净地附加到DataFrame？

根据docs，append（）将“DataFrame或Series / dict-like对象或其列表”作为参数。鉴于描述，我想到的是这样应该是可能的，但我找不到合适的语法：

df = pd.DataFrame(columns=('x', 'y', 'label'))
df.append([2, 4, 1]) # Does not work

我可以在df.loc[len(df)] = [4, 4, 1]附加一行，但这不是很干净。

Answer 1

DataFrame.append需要Series或DataFrame与index相同columns names或与df相同{/ 1}}：

df1 = pd.DataFrame([[2, 4, 1]], columns=('x', 'y', 'label'))
print (df1)
   x  y  label
0  2  4      1

df = df.append([pd.Series([4, 4, 1], index = df.columns)], ignore_index=True)
df = df.append(df1, ignore_index=True)
#your solution
df.loc[len(df)] = [4, 4, 1]
print (df)
     x    y  label
0  4.0  4.0    1.0
1  2.0  4.0    1.0
2  4.0  4.0    1.0

#dont align because default columns names
df = df.append([[4, 4, 1]])
print (df)
     x    y label    0    1    2
0  NaN  NaN   NaN  4.0  4.0  1.0

但是如果是默认列名：

df = pd.DataFrame(columns=range(3))
print (df)
Empty DataFrame
Columns: [0, 1, 2]
Index: []

df = df.append([[4, 4, 1]])
print (df)
     0    1    2
0  4.0  4.0  1.0

Answer 2

您也可以执行以下操作：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;


namespace WindowsFormsApplication24
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();

            string[] Paths = {
                "Home/Girls/Smoll",
                "Home/Girls/Pige",
                "Home/Girls/Manualy",
                "Home/Man/Smoll",
                "Home/Man/Pig",
                "index/domain/index",
                "index/ur"
            };
            List<List<string>> splitPaths = Paths.Select(x => x.Split(new char[] { '/' }).ToList()).ToList();
            TreeNode node = new TreeNode();
            RecursiveAdd(splitPaths, node);
            treeView1.Nodes.Add(node);
            treeView1.ExpandAll();
        }
        public void RecursiveAdd(List<List<string>> splitPaths, TreeNode node)
        {
            var groups = splitPaths.GroupBy(x => x[0]).ToList();
            foreach (var group in groups)
            {
                TreeNode childNode = node.Nodes.Add(group.Key);
                List<List<string>> children = group.Where(x => x.Count() > 1).Select(x => x.Skip(1).ToList()).ToList();
                RecursiveAdd(children, childNode);
            }
        }

    }

}

真的没办法少于那个。

Pandas append（）行具体示例

2 个答案: