- +在此添加单个AI新笔记
pandas列级df["新列名"] = 0新增列和基础值
![列级 - df["新列名"] = 0 - 新增列和基础值](/_next/image?url=https%3A%2F%2Fbookchips.com%2Fchips%2F6850eb130b9569655f1202d5%2F%E5%88%97%E7%BA%A7-df%5B_%E6%96%B0%E5%88%97%E5%90%8D_%5D%3D0-%E6%96%B0%E5%A2%9E%E5%88%97%E5%92%8C%E5%9F%BA%E7%A1%80%E5%80%BC.png&w=3840&q=85)
所有列后面添加新列
import numpy as npimport pandas as pddf = pd.DataFrame(data=[{"A":"one", "B":"a"}, {"A":"two", "B":np.nan}, {"A":"one", "B":1}])
| A | B | |
|---|---|---|
| 0 | one | a |
| 1 | two | NaN |
| 2 | one | 1 |
df["新列名"] = 0
不需要df_new = 返回
| A | B | 新列名 | |
|---|---|---|---|
| 0 | one | a | 0 |
| 1 | two | NaN | 0 |
| 2 | one | 1 | 0 |
指定位置添加新列
df.insert(第几列用int, '新列名', 基础值int或str等)df.insert(int, '新列名', new_value)df.insert(df.shape[1], '新列名', new_value) # 在最后一列加
int：指定列的列索引后面加
new_value:基础值
DataFrame信息 - df.shape[0] - [0]行数、[1]列数
import numpy as npimport pandas as pddf = pd.DataFrame(data=[{"A":"one", "B":"a"}, {"A":"two", "B":np.nan}, {"A":"one", "B":1}])
| A | B | |
|---|---|---|
| 0 | one | a |
| 1 | two | NaN |
| 2 | one | 1 |
df.insert(df.shape[1], '新列名', df['A'])
不需要df_new = 返回
| A | B | 新列名 | |
|---|---|---|---|
| 0 | one | a | one |
| 1 | two | NaN | two |
| 2 | one | 1 | one |
df第几列用int添加
import numpy as npimport pandas as pddf = pd.DataFrame(data=[{"A":"one", "B":"a"}, {"A":"two", "B":np.nan}, {"A":"one", "B":1}])print(df)df.insert(1, '新列名', df['A'])print(df)
