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Li Zheng flyskywhy@gmail.com

Python 使用详解

从预编译包安装 Python​

从 https://github.com/indygreg/python-build-standalone 下载预编译好的安装包，以cpython-3.11.10+20241016-x86_64_v3-unknown-linux-gnu-pgo+lto-full.tar.zst为例

cd /home/foobar/tools/ wget https://github.com/indygreg/python-build-standalone/releases/download/20241016/cpython-3.11.10+20241016-x86_64_v3-unknown-linux-gnu-pgo+lto-full.tar.zst tar axvf cpython-3.11.10+20241016-x86_64_v3-unknown-linux-gnu-pgo+lto-full.tar.zst mv python cpython-3.11.10 export PYTHONHOME=/home/foobar/tools/cpython-3.11.10/install export PYTHONPATH=/home/foobar/tools/cpython-3.11.10/install export PATH=/home/foobar/tools/cpython-3.11.10/install/bin:$PATH

从源码安装 Python​

以期望运行 https://github.com/Tianxiaomo/pytorch-YOLOv4/tool/darknet2pytorch.py 为例，在 git clone 下来之后的 pytorch-YOLOv4 目录中直接运行

python tool/darknet2pytorch.py

的话，会报错说

ModuleNotFoundError: No module named 'torch'

显然是先要运行

pip install -r requirements.txt

但运行到一半， requirements.txt 中的一个 module 会报错说当前运行的 python 版本太低，于是去 https://www.python.org/downloads/ 下载较新版本的 Python 3.10.12 ，而该网站针对 Linux 只提供了源代码下载来自己编译安装，于是

cd ~/tools/ wget https://www.python.org/ftp/python/3.10.12/Python-3.10.12.tgz tar axvf Python-3.10.12.tgz cd Python-3.10.12 ./configure make make test sudo make altinstall sudo update-alternatives --install /usr/bin/python python /usr/bin/python2 100 sudo update-alternatives --install /usr/bin/python python /usr/bin/python3 150 sudo update-alternatives --install /usr/bin/python python /usr/local/bin/python3.10 200 sudo update-alternatives --config python sudo update-alternatives --install /usr/bin/pip pip /usr/bin/pip2 100 sudo update-alternatives --install /usr/bin/pip pip /usr/bin/pip3 150 sudo update-alternatives --install /usr/bin/pip pip /usr/local/bin/pip3.10 200 sudo update-alternatives --config pip

编译过程中如果出现

fatal error: pip_ffi.h: No such file or directory

则需要

sudo apt install libffi-devel

并重新（最好先重新./configure）make

现在再次运行

cd pytorch-YOLOv4 pip install -r requirements.txt

如果出现错误

Could not fetch URL

则需要先

pip config set global.index-url https://mirrors.cloud.tencent.com/pypi/simple

（就会自动生成~/.pip/pip.ini 文件）来加以永久解决，或是在 pip install 后面临时加上参数

-i https://mirrors.cloud.tencent.com/pypi/simple --trusted-host mirrors.cloud.tencent.com

如果出现错误

pip is configured with locations that require TLS/SSL, however the ssl module in Python is not available

则可能是当前 Linux 中安装的 openssl 版本太旧而不符合太新版本的 Python 3.10.12 的需求，此时如果不想更新 openssl 版本的话，可以选择安装较旧版本的 Python 3.6.2

cd ~/tools/ wget https://www.python.org/ftp/python/3.6.2/Python-3.6.2.tgz tar axvf Python-3.6.2.tgz cd Python-3.6.2 ./configure make make test sudo make altinstall sudo update-alternatives --install /usr/bin/python python /usr/local/bin/python3.6 250 sudo update-alternatives --config python sudo update-alternatives --install /usr/bin/pip pip /usr/local/bin/pip3.6 250 sudo update-alternatives --config pip

然后如果仍然出现

pip is configured with locations that require TLS/SSL, however the ssl module in Python is not available

的话，则可以观察一下之前 make 时最后的输出

    Failed to find the necessary bits to build these modules:
    _bsddb             _curses            _curses_panel
    _hashlib           _sqlite3           _ssl   <----------

如果有 _ssl 在里面的，则需要

sudo apt install libssl-dev

并重新（最好先重新./configure）make

其它对应备忘

_dbm和_gdbm对应sudo apt install libgdbm-dev libgdbm-compat-dev

_tkinter对应sudo apt install tk-dev

readline对应sudo apt install libreadline-dev

如果出现错误

ModuleNotFoundError: No module named '_bz2'

则需要

sudo apt-get install libbz2-dev

并重新（最好先重新./configure）make

如果出现错误

Exception: Traceback (most recent call last): File "/usr/local/lib/python3.6/site-packages/pip/_internal/cli/base_command.py", line 143, in main ... pip._vendor.pytoml.core.TomlError: /tmp/pip-install-5q3n6wai/cmake/pyproject.toml(87, 1): msg You are using pip version 18.1, however version 21.3.1 is available. You should consider upgrading via the 'pip install --upgrade pip' command.

则需要升级 pip 版本

pip install --upgrade pip --user sudo update-alternatives --install /usr/bin/pip pip ~/.local/bin/pip3.6 300 sudo update-alternatives --config pip

后续如果碰到

ERROR: Could not find a version that satisfies the requirement

错误，升级 Python 也是一种解决方法，比如

cd ~/tools/ wget https://www.python.org/ftp/python/3.7.17/Python-3.7.17.tgz tar axvf Python-3.7.17.tgz cd Python-3.7.17 ./configure make make test sudo make altinstall sudo update-alternatives --install /usr/bin/python python /usr/local/bin/python3.7 350 sudo update-alternatives --config python sudo update-alternatives --install /usr/bin/pip pip /usr/local/bin/pip3.7 350 sudo update-alternatives --config pip

坑​

action='store_false'​

这个用于解决一个 PyTorch 问题的提交点 https://github.com/flyskywhy/YOLOv5-Lite/commit/bb07475 花了我几天时间去调试，然而究其原因只是 Python 的一个无聊设计——如果命令行参数被设计为 action='store_false' ，那就表示如果命令运行时没有写上该参数，则该命令就认为该参数为 True ，反之如果写上该参数，则反而为 False ——比较反人类的设计，很少有人会无聊到这样为自己的命令代码这样设计参数。

pip install 时报错no space left on device也就是/tmp/存储空间不够​

mkdir /home/foobar/a-big-tmp TMPDIR=/home/foobar/a-big-tmp/ pip install -r requirements.txt