try-except 带文件句柄（关闭的地方）

Question

假设我想在处理 txt 文件时引入一个 try-except 块。以下两种捕获可能异常的方式，哪一种是正确的？

try:
    h = open(filename)
except:
    h.close()
    print('Could not read file')



try:
    h = open(filename)
except:
  
    print('Could not read file')

换句话说，h.close()即使发生异常也要调用吗？

其次，假设你有如下代码

try:
    h = open(filename)
    "code line here1"
    "code line here2"
except:
    h.close()
    print('Could not read file')

如果“code line here1”中出现错误，我应该在 except 块中使用 h.close() 吗？

和之前的代码行有区别吗？

Answer 1

您应该使用 with，它会适当地关闭文件：

with open(filename) as h:
    #
    # do whatever you need...
    # 
# when you get here, the file will be closed automatically.

如果需要，您可以将其包含在 try/except 块中。文件将始终正确关闭：

try:
    with open(filename) as h:
        #
        # do whatever you need...
        #
except FileNotFoundError:
    print('file not found')

try-except 带文件句柄（关闭的地方）

try-except with files handle (where to close)

python

try-catch