python取特定列

data = [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
]

# 提取第二列（索引为1）
column = [row[1] for row in data]
print(column)  # 输出: [2, 5, 8]

import numpy as np

data = np.array([
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
])

# 提取第二列（索引为1）
column = data[:, 1]
print(column)  # 输出: [2 5 8]

import pandas as pd

data = pd.DataFrame({
    'A': [1, 4, 7],
    'B': [2, 5, 8],
    'C': [3, 6, 9]
})

# 提取'B'列
column = data['B']
print(column)  # 输出: 0    2
              #       1    5
              #       2    8
              #       Name: B, dtype: int64

# 错误示例
try:
    column = data[:, 10]  # 假设data只有3列
except IndexError as e:
    print(f"Error: {e}")

# 错误示例
try:
    column = data['D']  # 假设'D'列不存在
except KeyError as e:
    print(f"Error: {e}")