安裝pydensecrf時報錯：

            
              (venv) dorothy@dorothy-MS-7A94:~/project/venv/bin$ pip install pydensecrf
Collecting pydensecrf
  Using cached https://files.pythonhosted.org/packages/31/5a/1c2ab48e8019d282c128bc5c621332267bb954d32eecdda3ba57306b1551/pydensecrf-1.0rc3.tar.gz
Building wheels for collected packages: pydensecrf
  Running setup.py bdist_wheel for pydensecrf ... error
  Complete output from command /home/dorothy/project2/venv/bin/python -u -c "import setuptools, tokenize;__file__='/tmp/pip-build-6jjoctul/pydensecrf/setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" bdist_wheel -d /tmp/tmph56xsy38pip-wheel- --python-tag cp35:
  running bdist_wheel
  running build
  running build_py
  creating build
  creating build/lib.linux-x86_64-3.5
  creating build/lib.linux-x86_64-3.5/pydensecrf
  copying pydensecrf/__init__.py -> build/lib.linux-x86_64-3.5/pydensecrf
  copying pydensecrf/utils.py -> build/lib.linux-x86_64-3.5/pydensecrf
  running build_ext
  building 'pydensecrf.eigen' extension
  creating build/temp.linux-x86_64-3.5
  creating build/temp.linux-x86_64-3.5/pydensecrf
  x86_64-linux-gnu-gcc -pthread -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -g -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2 -fPIC -Ipydensecrf/densecrf/include -I/home/dorothy/project2/venv/include -I/usr/include/python3.5m -c pydensecrf/eigen.cpp -o build/temp.linux-x86_64-3.5/pydensecrf/eigen.o
  cc1plus: warning: command line option ‘-Wstrict-prototypes’ is valid for C/ObjC but not for C++
  pydensecrf/eigen.cpp:23:20: fatal error: Python.h: 沒有那個文件或目錄
  compilation terminated.
  error: command 'x86_64-linux-gnu-gcc' failed with exit status 1
  
  ----------------------------------------
  Failed building wheel for pydensecrf
  Running setup.py clean for pydensecrf
Failed to build pydensecrf
Installing collected packages: pydensecrf
  Running setup.py install for pydensecrf ... error
    Complete output from command /home/dorothy/project2/venv/bin/python -u -c "import setuptools, tokenize;__file__='/tmp/pip-build-6jjoctul/pydensecrf/setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" install --record /tmp/pip-hgybpc8s-record/install-record.txt --single-version-externally-managed --compile --install-headers /home/dorothy/project2/venv/include/site/python3.5/pydensecrf:
    running install
    running build
    running build_py
    creating build
    creating build/lib.linux-x86_64-3.5
    creating build/lib.linux-x86_64-3.5/pydensecrf
    copying pydensecrf/__init__.py -> build/lib.linux-x86_64-3.5/pydensecrf
    copying pydensecrf/utils.py -> build/lib.linux-x86_64-3.5/pydensecrf
    running build_ext
    building 'pydensecrf.eigen' extension
    creating build/temp.linux-x86_64-3.5
    creating build/temp.linux-x86_64-3.5/pydensecrf
    x86_64-linux-gnu-gcc -pthread -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -g -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2 -fPIC -Ipydensecrf/densecrf/include -I/home/dorothy/project2/venv/include -I/usr/include/python3.5m -c pydensecrf/eigen.cpp -o build/temp.linux-x86_64-3.5/pydensecrf/eigen.o
    cc1plus: warning: command line option ‘-Wstrict-prototypes’ is valid for C/ObjC but not for C++
    pydensecrf/eigen.cpp:23:20: fatal error: Python.h: 沒有那個文件或目錄
    compilation terminated.
    error: command 'x86_64-linux-gnu-gcc' failed with exit status 1
    
    ----------------------------------------
Command "/home/dorothy/project2/venv/bin/python -u -c "import setuptools, tokenize;__file__='/tmp/pip-build-6jjoctul/pydensecrf/setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" install --record /tmp/pip-hgybpc8s-record/install-record.txt --single-version-externally-managed --compile --install-headers /home/dorothy/project2/venv/include/site/python3.5/pydensecrf" failed with error code 1 in /tmp/pip-build-6jjoctul/pydensecrf/
You are using pip version 9.0.1, however version 19.2.2 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.
            
          

解決方法：

在

            
              pip install pydensecrf
            
          

之前加上sudo，即：

            
              (venv) dorothy@dorothy-MS-7A94:~/project/venv/bin$ sudo pip install pydensecrf
sudo: /etc/sudoers.d 可被任何人寫
The directory '/home/dorothy/.cache/pip/http' or its parent directory is not owned by the current user and the cache has been disabled. Please check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.
The directory '/home/dorothy/.cache/pip' or its parent directory is not owned by the current user and caching wheels has been disabled. check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.
Collecting pydensecrf
  Downloading https://files.pythonhosted.org/packages/31/5a/1c2ab48e8019d282c128bc5c621332267bb954d32eecdda3ba57306b1551/pydensecrf-1.0rc3.tar.gz (1.0MB)
    100% |████████████████████████████████| 1.0MB 173kB/s 
Installing collected packages: pydensecrf
  Running setup.py install for pydensecrf ... done
Successfully installed pydensecrf-1.0rc3
You are using pip version 8.1.1, however version 19.2.2 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.

            
          

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