获取 os.path.join 以使用生成器

Question

试图让这行代码工作，无论我如何更改格式，我都会遇到问题：

if not os.path.exists(os.path.join(IncludeSettings.FILE_URL, [str(x) for x in [year, month, day]])):

（年、月、日）可以是整数或字符串。

追踪：

Traceback (most recent call last):
  File "/home/tinyup/dev/lib/python2.7/site-packages/pyramid_debugtoolbar-1.0.3-py2.7.egg/pyramid_debugtoolbar/toolbar.py", line 117, in toolbar_tween
    response = _handler(request)
  File "/home/tinyup/dev/lib/python2.7/site-packages/pyramid_debugtoolbar-1.0.3-py2.7.egg/pyramid_debugtoolbar/panels/performance.py", line 55, in resource_timer_handler
    result = handler(request)
  File "/home/tinyup/dev/lib/python2.7/site-packages/pyramid-1.4a3-py2.7.egg/pyramid/tweens.py", line 20, in excview_tween
    response = handler(request)
  File "/home/tinyup/dev/lib/python2.7/site-packages/pyramid-1.4a3-py2.7.egg/pyramid/router.py", line 161, in handle_request
    response = view_callable(context, request)
  File "/home/tinyup/dev/lib/python2.7/site-packages/pyramid-1.4a3-py2.7.egg/pyramid/config/views.py", line 342, in rendered_view
    result = view(context, request)
  File "/home/tinyup/dev/lib/python2.7/site-packages/pyramid-1.4a3-py2.7.egg/pyramid/config/views.py", line 456, in _class_requestonly_view
    response = getattr(inst, attr)()
  File "/home/tinyup/dev/tinyuploads/tinyuploads/views/share.py", line 56, in view_process
    return self.handle_file_upload(self.request.params['file'], shareID)
  File "/home/tinyup/dev/tinyuploads/tinyuploads/views/share.py", line 101, in handle_file_upload
    self.save(file, newFileName, isImage, uploadTime)
  File "/home/tinyup/dev/tinyuploads/tinyuploads/views/share.py", line 166, in save
    if not os.path.exists(os.path.join(IncludeSettings.FILE_URL, [str(x) for x in [year, month, day]])):
  File "/home/tinyup/dev/lib/python2.7/posixpath.py", line 66, in join
    if b.startswith('/'):
AttributeError: 'list' object has no attribute 'startswith'

Answer 1

您在此处缺少"*"：

>>> os.path.join('foo', *['a','b'])
'foo/a/b'

您必须在此处使用 star 运算符才能将列表项作为解压缩的变量参数列表传递给该方法。

Answer 2

@user1833746首先有了答案，所以如果你接受其中任何一个，接受那个:)

除了解包之外，如果您不打算使用结果列表，您还可以将[更改为(，使其成为真正的生成器（而不是创建一个列表然后迭代它）。*运算符"解包"，这意味着项目的各个组件将被传递给函数。正如您在下面的代码中看到的，os.path.join接受"两个"参数：a（路径名）和*p（任意数量的路径组件）。如您所见，您可以使用此语法提供任意数量的附加路径名参数（即没有固定的path_component1、path_component2变量）。在您的情况下，一旦你得到了你的值生成器，你就把它们"解包"成单独的值（而不是单个list或generator对象），然后os.path.join函数处理：

In [1]: import os
In [2]: os.path.join('/home/myname', *(str(x) for x in ('one', 'two', 'three')))
Out[2]: '/home/myname/one/two/three'
In [3]: os.path.join??
Type:           function
Base Class:     <type 'function'>
String Form:    <function join at 0x7f4944c31a28>
Namespace:      Interactive
File:           /usr/lib/python2.6/posixpath.py
Definition:     os.path.join(a, *p)
Source:
def join(a, *p):
    """Join two or more pathname components, inserting '/' as needed.
    If any component is an absolute path, all previous path components
    will be discarded."""
    path = a
    for b in p:
        if b.startswith('/'):
            path = b
        elif path == '' or path.endswith('/'):
            path +=  b
        else:
            path += '/' + b
    return path

Answer 3

在[str(x) for x in [year, month, day]]前添加 *

*[str(x) for x in [year, month, day]]

Answer 4

if not os.path.exists(os.path.join(IncludeSettings.FILE_URL, str(year), str(month), str(day))):

为了可读性：

fname = os.path.join(IncludeSettings.FILE_URL, str(year), str(month), str(day))
if not os.path.exists(fname):