如何在循环中传递csv的标头

Question

我想循环创建一个csv文件。但是，当我这样做时，它也会同时写标题部分。如何只写一次标题部分？

fieldnames=['numbers']
for i in range(0,100):
    with open('numbers.csv','a',newline='') as csvfile:
        writer=csv.Dictwriter(csvfile,fieldnames=fieldnames,lineterminator='\n')
        writer.writeheader()
        writer.writerow({'numbers':i})

Answer 1

非常简单：将这部分移出循环（似乎很明显...）。您绝对不想在每次迭代中都重新打开文件（打开文件-关闭FWIW绝非免费）：

fieldnames=['numbers']
with open('numbers.csv','a',newline='') as csvfile:
    writer = csv.Dictwriter(csvfile,fieldnames=fieldnames,lineterminator='\n')
    writer.writeheader()
    for i in range(100):
        writer.writerow({'numbers':i})