配置python 环境时，遇到关于 lmdb 模块的问题。

工作需要，下载 rknn-toolkit 开发套件时，需要事先进行python 环境配置，然后就遇到这个问题，卡了我好久。。。。。（还是自己菜，唉。）BUG具体如下：**
这是开始的命令，它就是BUG的潘多拉魔盒：

(venv) shopping1@ubuntu:~/rk3399pro_linux/external/rknn-toolkit/packages$ pip install -r ./requirements-cpu.txt

** 中间有很长一段是第三方库安装成功的记录，就不给你们看了，直接看BUG处吧，下面其实有大半都是红色字体，复制过来我不会弄，搞成全是一样的颜色了。：**

Using cached https://files.pythonhosted.org/packages/c0/4e/fd492e91abdc2d2fcb70ef453064d980688762079397f779758e055f6575/Markdown-3.1.1-py2.py3-none-any.whl
Building wheels for collected packages: lmdb
  Building wheel for lmdb (setup.py) ... error
  ERROR: Complete output from command /home/shopping1/venv/bin/python3 -u -c 'import setuptools, tokenize;__file__='"'"'/tmp/pip-install-vg8t53ai/lmdb/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/pip-wheel-u2ozrkg_ --python-tag cp36:
  ERROR: py-lmdb: Using bundled liblmdb; override with LMDB_FORCE_SYSTEM=1.
  py-lmdb: Using CPython extension; override with LMDB_FORCE_CFFI=1.
  running bdist_wheel
  running build
  running build_py
  creating build
  creating build/lib.linux-x86_64-3.6
  creating build/lib.linux-x86_64-3.6/lmdb
  copying lmdb/cffi.py -> build/lib.linux-x86_64-3.6/lmdb
  copying lmdb/__main__.py -> build/lib.linux-x86_64-3.6/lmdb
  copying lmdb/tool.py -> build/lib.linux-x86_64-3.6/lmdb
  copying lmdb/_config.py -> build/lib.linux-x86_64-3.6/lmdb
  copying lmdb/__init__.py -> build/lib.linux-x86_64-3.6/lmdb
  running build_ext
  building 'cpython' extension
  creating build/temp.linux-x86_64-3.6
  creating build/temp.linux-x86_64-3.6/lmdb
  creating build/temp.linux-x86_64-3.6/lib
  x86_64-linux-gnu-gcc -pthread -DNDEBUG -g -fwrapv -O2 -Wall -g -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2 -fPIC -Ilib/py-lmdb -Ilib -I/usr/include/python3.6m -I/home/shopping1/venv/include/python3.6m -c lmdb/cpython.c -o build/temp.linux-x86_64-3.6/lmdb/cpython.o -UNDEBUG -w
  lmdb/cpython.c:42:10: fatal error: Python.h: No such file or directory
   #include "Python.h"
            ^~~~~~~~~~
  compilation terminated.
  error: command 'x86_64-linux-gnu-gcc' failed with exit status 1
  ----------------------------------------
  ERROR: Failed building wheel for lmdb
  Running setup.py clean for lmdb
Failed to build lmdb
Installing collected packages: lmdb, decorator, networkx, typing, typing-extensions, onnx, itsdangerous, MarkupSafe, Jinja2, click, Werkzeug, flask, dill, opencv-python, ruamel.yaml, wrapt, keras-applications, tensorflow-estimator, grpcio, gast, keras-preprocessing, absl-py, markdown, tensorboard, google-pasta, astor, termcolor, tensorflow
  Running setup.py install for lmdb ... error
    ERROR: Complete output from command /home/shopping1/venv/bin/python3 -u -c 'import setuptools, tokenize;__file__='"'"'/tmp/pip-install-vg8t53ai/lmdb/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-record-yamu_5n9/install-record.txt --single-version-externally-managed --compile --install-headers /home/shopping1/venv/include/site/python3.6/lmdb:
    ERROR: py-lmdb: Using bundled liblmdb; override with LMDB_FORCE_SYSTEM=1.
    py-lmdb: Using CPython extension; override with LMDB_FORCE_CFFI=1.
    running install
    running build
    running build_py
    creating build
    creating build/lib.linux-x86_64-3.6
    creating build/lib.linux-x86_64-3.6/lmdb
    copying lmdb/cffi.py -> build/lib.linux-x86_64-3.6/lmdb
    copying lmdb/__main__.py -> build/lib.linux-x86_64-3.6/lmdb
    copying lmdb/tool.py -> build/lib.linux-x86_64-3.6/lmdb
    copying lmdb/_config.py -> build/lib.linux-x86_64-3.6/lmdb
    copying lmdb/__init__.py -> build/lib.linux-x86_64-3.6/lmdb
    running build_ext
    building 'cpython' extension
    creating build/temp.linux-x86_64-3.6
    creating build/temp.linux-x86_64-3.6/lmdb
    creating build/temp.linux-x86_64-3.6/lib
    x86_64-linux-gnu-gcc -pthread -DNDEBUG -g -fwrapv -O2 -Wall -g -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2 -fPIC -Ilib/py-lmdb -Ilib -I/usr/include/python3.6m -I/home/shopping1/venv/include/python3.6m -c lmdb/cpython.c -o build/temp.linux-x86_64-3.6/lmdb/cpython.o -UNDEBUG -w
    lmdb/cpython.c:42:10: fatal error: Python.h: No such file or directory
     #include "Python.h"
              ^~~~~~~~~~
    compilation terminated.
    error: command 'x86_64-linux-gnu-gcc' failed with exit status 1
    ----------------------------------------
ERROR: Command "/home/shopping1/venv/bin/python3 -u -c 'import setuptools, tokenize;__file__='"'"'/tmp/pip-install-vg8t53ai/lmdb/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-record-yamu_5n9/install-record.txt --single-version-externally-managed --compile --install-headers /home/shopping1/venv/include/site/python3.6/lmdb" failed with error code 1 in /tmp/pip-install-vg8t53ai/lmdb/

回到主题，字里行间都提到 lmdb 这个库，所以我猜想是不是它没法安装引起的，于是想到自己手动安装。一开始输入 python ，进入python 命令行里下载，结果不行：

(venv) shopping1@ubuntu:~/rk3399pro_linux/external/rknn-toolkit/packages$ python
Python 3.6.8 (default, Jan 14 2019, 11:02:34) 
[GCC 8.0.1 20180414 (experimental) [trunk revision 259383]] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> pip install lmdb
  File "", line 1
    pip install lmdb
              ^
SyntaxError: invalid syntax
>>> pip install lmdb
  File "", line 1
    pip install lmdb
              ^
SyntaxError: invalid syntax
>>> quit()

后来退出 python 命令行，在ubuntu 终端里，输入以下命令：

(venv) shopping1@ubuntu:~/rk3399pro_linux/external/rknn-toolkit/packages$ pip install lmdb
Collecting lmdb
  Using cached https://files.pythonhosted.org/packages/86/5c/6ad690daeaa00b328606bf2fa435244a11cc2dd9aedac6ef4d2ef2a21f6e/lmdb-0.96.tar.gz
Building wheels for collected packages: lmdb
  Building wheel for lmdb (setup.py) ... error
  ERROR: Complete output from command /home/shopping1/venv/bin/python3 -u -c 'import setuptools, tokenize;__file__='"'"'/tmp/pip-install-bzqbulh7/lmdb/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/pip-wheel-dnybrxi9 --python-tag cp36:
  ERROR: py-lmdb: Using bundled liblmdb; override with LMDB_FORCE_SYSTEM=1.
  py-lmdb: Using CPython extension; override with LMDB_FORCE_CFFI=1.
  running bdist_wheel
  running build
  running build_py
  creating build
  creating build/lib.linux-x86_64-3.6
  creating build/lib.linux-x86_64-3.6/lmdb
  copying lmdb/cffi.py -> build/lib.linux-x86_64-3.6/lmdb
  copying lmdb/__main__.py -> build/lib.linux-x86_64-3.6/lmdb
  copying lmdb/tool.py -> build/lib.linux-x86_64-3.6/lmdb
  copying lmdb/_config.py -> build/lib.linux-x86_64-3.6/lmdb
  copying lmdb/__init__.py -> build/lib.linux-x86_64-3.6/lmdb
  running build_ext
  building 'cpython' extension
  creating build/temp.linux-x86_64-3.6
  creating build/temp.linux-x86_64-3.6/lmdb
  creating build/temp.linux-x86_64-3.6/lib
  x86_64-linux-gnu-gcc -pthread -DNDEBUG -g -fwrapv -O2 -Wall -g -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2 -fPIC -Ilib/py-lmdb -Ilib -I/usr/include/python3.6m -I/home/shopping1/venv/include/python3.6m -c lmdb/cpython.c -o build/temp.linux-x86_64-3.6/lmdb/cpython.o -UNDEBUG -w
  lmdb/cpython.c:42:10: fatal error: Python.h: No such file or directory
   #include "Python.h"
            ^~~~~~~~~~
  compilation terminated.
  error: command 'x86_64-linux-gnu-gcc' failed with exit status 1
  ----------------------------------------
  ERROR: Failed building wheel for lmdb
  Running setup.py clean for lmdb
Failed to build lmdb
Installing collected packages: lmdb
  Running setup.py install for lmdb ... error
    ERROR: Complete output from command /home/shopping1/venv/bin/python3 -u -c 'import setuptools, tokenize;__file__='"'"'/tmp/pip-install-bzqbulh7/lmdb/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-record-7cmwe2vk/install-record.txt --single-version-externally-managed --compile --install-headers /home/shopping1/venv/include/site/python3.6/lmdb:
    ERROR: py-lmdb: Using bundled liblmdb; override with LMDB_FORCE_SYSTEM=1.
    py-lmdb: Using CPython extension; override with LMDB_FORCE_CFFI=1.
    running install
    running build
    running build_py
    creating build
    creating build/lib.linux-x86_64-3.6
    creating build/lib.linux-x86_64-3.6/lmdb
    copying lmdb/cffi.py -> build/lib.linux-x86_64-3.6/lmdb
    copying lmdb/__main__.py -> build/lib.linux-x86_64-3.6/lmdb
    copying lmdb/tool.py -> build/lib.linux-x86_64-3.6/lmdb
    copying lmdb/_config.py -> build/lib.linux-x86_64-3.6/lmdb
    copying lmdb/__init__.py -> build/lib.linux-x86_64-3.6/lmdb
    running build_ext
    building 'cpython' extension
    creating build/temp.linux-x86_64-3.6
    creating build/temp.linux-x86_64-3.6/lmdb
    creating build/temp.linux-x86_64-3.6/lib
    x86_64-linux-gnu-gcc -pthread -DNDEBUG -g -fwrapv -O2 -Wall -g -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2 -fPIC -Ilib/py-lmdb -Ilib -I/usr/include/python3.6m -I/home/shopping1/venv/include/python3.6m -c lmdb/cpython.c -o build/temp.linux-x86_64-3.6/lmdb/cpython.o -UNDEBUG -w
    lmdb/cpython.c:42:10: fatal error: Python.h: No such file or directory
     #include "Python.h"
              ^~~~~~~~~~
    compilation terminated.
    error: command 'x86_64-linux-gnu-gcc' failed with exit status 1
    ----------------------------------------
ERROR: Command "/home/shopping1/venv/bin/python3 -u -c 'import setuptools, tokenize;__file__='"'"'/tmp/pip-install-bzqbulh7/lmdb/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-record-7cmwe2vk/install-record.txt --single-version-externally-managed --compile --install-headers /home/shopping1/venv/include/site/python3.6/lmdb" failed with error code 1 in /tmp/pip-install-bzqbulh7/lmdb/

发现这个错误和上面的错误是一样的，这证明我的猜想是对的，BUG和 lmdb 有关，于是再次输入：

(venv) shopping1@ubuntu:~/rk3399pro_linux/external/rknn-toolkit/packages$ sudo pip install lmdb
[sudo] password for shopping1: 
The directory '/home/shopping1/.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/shopping1/.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 lmdb
  Downloading https://files.pythonhosted.org/packages/86/5c/6ad690daeaa00b328606bf2fa435244a11cc2dd9aedac6ef4d2ef2a21f6e/lmdb-0.96.tar.gz (869kB)
    100% |████████████████████████████████| 870kB 22kB/s 
Installing collected packages: lmdb
  Running setup.py install for lmdb ... done
Successfully installed lmdb-0.96

试着这样输入，结果成功安装，当时真快要叫出来，不过还好没叫，很快就打脸了。

(venv) shopping1@ubuntu:~/rk3399pro_linux/external/rknn-toolkit/packages$ pip install -r ./requirements-cpu.txt

再次输入这个鬼命令，满心欢喜的等待它全部KO的时候，又报错了，和上面一样，草。在怀疑自己刚才是不是真的成功安装了 lmdb 时，输入下面命令看了一样，启发了我：

(venv) shopping1@ubuntu:~/rk3399pro_linux/external/rknn-toolkit/packages$ sudo pip install lmdb
The directory '/home/shopping1/.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/shopping1/.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.
Requirement already satisfied: lmdb in /usr/local/lib/python2.7/dist-packages

可以看见该库安装在 python 2.7下面，而我输入以下：

(venv) shopping1@ubuntu:~/rk3399pro_linux/external/rknn-toolkit/packages$ python --version
Python 3.6.8

这两个对不上，所以怀疑是不是库默认安装路径错，应该安装在python3.6下面。所以，有以下操作。
先卸载 lmdb 库：

(venv) shopping1@ubuntu:/usr/local/lib/python3.6/dist-packages$ sudo pip uninstall lmdb
[sudo] password for shopping1: 
The directory '/home/shopping1/.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.
Uninstalling lmdb-0.96:
  /usr/local/lib/python2.7/dist-packages/lmdb-0.96-py2.7.egg-info
  /usr/local/lib/python2.7/dist-packages/lmdb/__init__.py
  /usr/local/lib/python2.7/dist-packages/lmdb/__init__.pyc
  /usr/local/lib/python2.7/dist-packages/lmdb/__main__.py
  /usr/local/lib/python2.7/dist-packages/lmdb/__main__.pyc
  /usr/local/lib/python2.7/dist-packages/lmdb/_config.py
  /usr/local/lib/python2.7/dist-packages/lmdb/_config.pyc
  /usr/local/lib/python2.7/dist-packages/lmdb/cffi.py
  /usr/local/lib/python2.7/dist-packages/lmdb/cffi.pyc
  /usr/local/lib/python2.7/dist-packages/lmdb/cpython.so
  /usr/local/lib/python2.7/dist-packages/lmdb/tool.py
  /usr/local/lib/python2.7/dist-packages/lmdb/tool.pyc
Proceed (y/n)? y
  Successfully uninstalled lmdb-0.96

再重新安装，记得加好路径，而且该路径是你目前使用 python 版本的路径，这点要记得。

(venv) shopping1@ubuntu:/usr/local/lib/python3.6/dist-packages$ sudo pip install --target=./ lmdb
The directory '/home/shopping1/.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/shopping1/.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 lmdb
  Downloading https://files.pythonhosted.org/packages/86/5c/6ad690daeaa00b328606bf2fa435244a11cc2dd9aedac6ef4d2ef2a21f6e/lmdb-0.96.tar.gz (869kB)
    100% |████████████████████████████████| 870kB 20kB/s 
Installing collected packages: lmdb
  Running setup.py install for lmdb ... done
Successfully installed lmdb-0.96

因为我在目标目录里，所以这样写，你们不要学我啊！！！ 之后再次输入命令：

(venv) shopping1@ubuntu:~/rk3399pro_linux/external/rknn-toolkit/packages$ sudo pip install -r ./requirements-cpu.txt

在揪心了几分钟后，终于好了，BUG解除！！！发个纪录，分享一下喜悦。

Successfully uninstalled tensorflow-0.9.0
Successfully installed Jinja2-2.10.1 MarkupSafe-1.1.1 Werkzeug-0.15.5 absl-py-0.7.1 astor-0.8.0
backports.weakref-1.0.post1 click-7.0 decorator-4.4.0 dill-0.2.8.2 flask-1.1.1 flatbuffers-1.9 funcsigs-1.0.2 
futures-3.3.0 gast-0.2.2 google-pasta-0.1.7 grpcio-1.22.0 h5py-2.9.0 itsdangerous-1.1.0 
keras-applications-1.0.8 keras-preprocessing-1.1.0 lmdb-0.96 markdown-3.1.1 mock-3.0.5 networkx-1.11 onnx-1.5.0 
opencv-python-4.1.0.25 protobuf-3.9.0 ruamel.ordereddict-0.4.13 ruamel.yaml-0.15.82 scipy-1.2.2 tensorboard-1.14.0 
tensorflow-1.14.0 tensorflow-estimator-1.14.0 termcolor-1.1.0 typing-3.7.4 typing-extensions-3.7.4 wrapt-1.11.2

这个鬼东西卡了我好几个小时，特意发帖纪录，共同进步！！！