Python3.x 如何区分文件之类的对象和文件路径之类的对象

就我个人而言，这是一个固执己见的答案，判断类文件对象的属性以进行所需的操作是a pythonic方法来确定对象的类型，因为这是pythonic duck tests/duck-typing的本质:

Duck类型在Python中大量使用，典型的例子是类似文件的类(例如，cStringIO允许将Python字符串视为文件).

Or from the python docs’ definition of duck-typing

一种编程风格，它不查看对象的类型来确定它是否有正确的接口；相反，方法或属性只是通过强调接口而不是特定类型来调用或使用("If it looks like a duck and quacks like a duck, it must be a duck.")，精心设计的代码通过允许多态替换来提高其灵活性.Duck类型避免使用type()或isinstance()进行测试.(但是请注意，duck类型可以用抽象基类来补充.)相反，它通常使用hasattr()个测试或EAFP编程.

如果您强烈地感到，仅仅判断接口的适用性是不够的，有一些非常好的理由，那么您可以反转测试并测试basestring或str，以测试所提供的对象是否与路径类似.测试将根据您的python版本而有所不同.

is_file_like = not isinstance(fp, basestring) # python 2
is_file_like = not isinstance(fp, str) # python 3

在任何情况下，对于您的上下文管理器，我都会继续制作一个完整的对象，如下图所示，以便包装您正在寻找的功能.

class SpiffyContextGuard(object):
    def __init__(self, spiffy_obj, file, mode, closefd=True):
        self.spiffy_obj = spiffy_obj
        is_file_like = all(hasattr(attr) for attr in ('seek', 'close', 'read', 'write'))
        self.fp = file if is_file_like else open(file, mode)
        self.closefd = closefd

    def __enter__(self):
        return self.fp

    def __exit__(self, type_, value, traceback):
        generated = '\n'.join(self.spiffy_obj.gen_file())
        self.fp.write(generated)
        if self.closefd:
            self.fp.__exit__()

然后像这样使用:

with SpiffyContextGuard(obj, 'hamlet.txt', 'w', True) as f:
    f.write('Oh that this too too sullied flesh\n')

fp = open('hamlet.txt', 'a')
with SpiffyContextGuard(obj, fp, 'a', False) as f:
    f.write('Would melt, thaw, resolve itself into a dew\n')

with SpiffyContextGuard(obj, fp, 'a', True) as f:
    f.write('Or that the everlasting had not fixed his canon\n')

如果要使用try/catch语义判断类型适合性，还可以将要在上下文保护上公开的文件操作包装起来:

class SpiffyContextGuard(object):
    def __init__(self, spiffy_obj, file, mode, closefd=True):
        self.spiffy_obj = spiffy_obj
        self.fp = self.file_or_path = file 
        self.mode = mode
        self.closefd = closefd

    def seek(self, offset, *args):
        try:
            self.fp.seek(offset, *args)
        except AttributeError:
            self.fp = open(self.file_or_path, mode)
            self.fp.seek(offset, *args)

    # define wrappers for write, read, etc., as well

    def __enter__(self):
        return self

    def __exit__(self, type_, value, traceback):
        generated = '\n'.join(self.spiffy_obj.gen_file())
        self.write(generated)
        if self.closefd:
            self.fp.__exit__()