一个上下文管理器而不是两个用于打开文件？

Question

我的问题看起来与类似，但不确定...我想解析一些有时用 gzip 压缩有时不用的日志文件。

我有以下内容：

if file[-3:] == ".gz":
     with gzip.open(file, 'rb') as f:
          # do something
else:
    with open(file) as f:
          # do the same thing.

是否可以只有一个 with 语句？

Answer 1

把你的"Do Something"放在一个函数中

def processFile(f)
        Do Something...

if file[-3:] == ".gz":
     with gzip.open(file, 'rb') as f:
          processFile(f)
else:
    with open(file) as f:
          processFile(f)

Answer 2

fn = gzip.open if file.endswith('.gz') else open

with fn(file, 'rb') as f:
    ...

另请注意，调用返回上下文管理器的函数不必发生在 with 行内：

if file.endswith('.gz'):
    ctx = gzip.open(file, 'rb')
else:
    ctx = open(file)

with ctx as f:
    ...

Answer 3

你可以把条件语句放在with行：

with gzip.open(file, 'rb') if file[-3:] == '.gz' else open(file) as f:
   processFile(f)

一个上下文管理器而不是两个用于打开文件？

One context manager instead of two for open file?

python

with-statement

python-3.x