我的Ubuntu 10.04附带了Python 2.6。现在，我还安装了Python 2.7，这是现在的系统默认值，因为当我从终端启动python时，它会启动Python 2.7。
现在，我想使用pip安装库pysftp，但我很难做到这一点。下面是我尝试的一些结果和结论。我做了pip install pysftp，但它说：

Downloading/unpacking pysftp
  Running setup.py egg_info for package pysftp
    Traceback (most recent call last):
      File "<string>", line 3, in <module>
      File "/usr/local/lib/python2.6/dist-packages/setuptools/__init__.py", line 12, in <module>
        from setuptools.extension import Extension
      File "/usr/local/lib/python2.6/dist-packages/setuptools/extension.py", line 8, in <module>
        from .dist import _get_unpatched
      File "/usr/local/lib/python2.6/dist-packages/setuptools/dist.py", line 21, in <module>
        packaging = pkg_resources.packaging
    AttributeError: 'module' object has no attribute 'packaging'
    Complete output from command python setup.py egg_info:
    Traceback (most recent call last):
  File "<string>", line 3, in <module>
  File "/usr/local/lib/python2.6/dist-packages/setuptools/__init__.py", line 12, in <module>
    from setuptools.extension import Extension
  File "/usr/local/lib/python2.6/dist-packages/setuptools/extension.py", line 8, in <module>
    from .dist import _get_unpatched
  File "/usr/local/lib/python2.6/dist-packages/setuptools/dist.py", line 21, in <module>
    packaging = pkg_resources.packaging
AttributeError: 'module' object has no attribute 'packaging'
----------------------------------------
Command python setup.py egg_info failed with error code 1
Storing complete log in ./pip-log.txt

字符串
在我看来，pip（显然是在Python 2.7安装之前安装的）链接到旧版本的Python，它不支持pysftp。还因为当我执行pip --version时，它说：

pip 0.3.1 from /usr/lib/python2.6/dist-packages (python 2.6)

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当我执行whereis python时，它会给我以下信息：

python: /usr/src/Python-2.7.10/python /usr/bin/python2.6 /usr/bin/python /etc/python2.6 /etc/python /usr/lib/python2.6 /usr/lib/python3.1 /usr/lib64/python2.6 /usr/lib64/python3.1 /usr/local/bin/python2.7-config /usr/local/bin/python /usr/local/bin/python2.7 /usr/local/lib/python2.6 /usr/local/lib/python2.7 /usr/include/python2.6 /usr/share/python /usr/share/man/man1/python.1.gz

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如何安装pysftp？