Question

当使用Python代码中的多个文件时，使用推荐的样式时会变得很丑：

with open("foo.txt") as foo:
    with open("bar.txt", "w") as bar:
         with open("baz.txt", "w") as baz:
              # Read from foo, write different output to bar an baz

只有处理文件的三个缩进级别！替代方案是这个

foo = open("foo.txt")
bar = open("bar.txt", "w")
baz = open("baz.txt", "w")
# Read from foo, write different output to bar an baz
foo.close()
bar.close()
baz.close()

我觉得这些例子中的任何一个都可以重构为更优雅的东西。有什么例子吗？

Answer 1

Python 2.7及更高版本允许您在一个with语句中指定多个上下文管理器：

with open("foo.txt") as foo, open("bar.txt", "w") as bar, open("baz.txt", "w") as baz:
    # Read from foo, write different output to bar an baz

行行变长，你不能使用括号将其保持在80个字符以下。但是，您可以使用\反斜杠延续：

with open("foo.txt") as foo,\
        open("bar.txt", "w") as bar,\
        open("baz.txt", "w") as baz:
    # Read from foo, write different output to bar an baz

另一个选择是使用contextlib.ExitStack() context manager（仅在Python 3.3及更高版本中）：

from contextlib import ExitStack

with ExitStack() as stack:
    foo = stack.enter_context(open("foo.txt"))
    bar = stack.enter_context(open("bar.txt"))
    baz = stack.enter_context(open("baz.txt"))

在Python中处理多个文件时，如何避免使用嵌套的“with”语句

1 个答案: