Python不创建新的文件头时，它不存在

Question

如果CSV文件不存在，我想写一个新的CSV文件，并在其中附加行数据。不确定以下代码为什么不添加文件头？（罚款）

import os
import csv

path = "test.csv"


with open(path, mode="a") as f:    
    writer = csv.writer(f, delimiter=",", quotechar='"', quoting=csv.QUOTE_MINIMAL)

    if not os.path.exists(path):
        writer.writerow(["col1", "col2", "col3", "col4", "col5", "col6", "col7"])

    row = [1,2,3,4,5,6,7]
    writer.writerow(row)

Answer 1

在打开文件之前，需要移动（如果存在）测试。如果文件不存在，以“a”模式打开文件将创建该文件。

import os
import csv

path = "test.csv"

exists = os.path.exists(path)
with open(path, mode="a") as f:    
    writer = csv.writer(f, delimiter=",", quotechar='"', quoting=csv.QUOTE_MINIMAL)

    if not exists:
        writer.writerow(["col1", "col2", "col3", "col4", "col5", "col6", "col7"])

    row = [1,2,3,4,5,6,7]
    writer.writerow(row)