安装Fastapi依赖时报错OSError: [WinError 2] 系统找不到指定文件如何解决

问题复现 #

执行pip install Fastapi[all]命令安装FastAPI全量框架依赖，安装包全部下载完成后，安装阶段抛出如下错误：

Using legacy 'setup.py install' for python-multipart, since package 'wheel' is not installed.

WARNING: Ignoring invalid distribution -ip (c:\\python39\\lib\\site-packages)
WARNING: Ignoring invalid distribution - (c:\\python39\\lib\\site-packages)

Installing collected packages: sniffio, idna, colorama, typing-extensions, h11, click, anyio, websockets, watchgod, uvicorn, urllib3, starlette, six, pyyaml, 
python-dotenv, pydantic, MarkupSafe, httptools, dnspython, charset-normalizer, certifi, ujson, requests, python-multipart, orjson, jinja2, itsdangerous, fastapi, email-validator

  WARNING: Failed to write executable - trying to use .deleteme logic
ERROR: Could not install packages due to an OSError: [WinError 2] The system cannot find the file specified: 'c:\\python39\\Scripts\\watchgod.exe' -> 'c:\\python39\\Scripts\\watchgod.exe.deleteme'

WARNING: Ignoring invalid distribution -ip (c:\\python39\\lib\\site-packages)
WARNING: Ignoring invalid distribution - (c:\\python39\\lib\\site-packages)
WARNING: Ignoring invalid distribution -ip (c:\\python39\\lib\\site-packages)
WARNING: Ignoring invalid distribution - (c:\\python39\\lib\\site-packages)

运行环境 #

• Python版本：Python 3.10.0
• pip版本：pip 21.3 来自c:\python39\lib\site-packages\pip (python 3.9)

错误原因 #

1. 权限不足：Windows系统当前终端无Python安装目录的写入权限，无法重命名Scripts目录下的可执行文件，触发watchgod.exe写入失败报错
2. 环境版本不匹配：本地同时存在Python3.9和Python3.10两个版本，当前调用的pip对应Python3.9，和实际使用的Python3.10环境不一致，出现路径冲突
3. 存在破损依赖：site-packages目录下有安装中断产生的无效破损包，干扰安装流程
4. 缺少wheel依赖：部分包只能用旧版setup.py方式安装，兼容问题多

解决步骤 #

• 以管理员身份运行终端（命令提示符/PowerShell），获取Python目录写入权限
• 统一Python与pip调用版本，执行以下命令确认版本匹配：

  py -3.10 -m pip --version
  

  确认输出的pip信息对应Python3.10后，后续所有pip操作均使用py -3.10 -m pip install 包名格式执行，避免版本调用混乱
• 清理破损依赖包：进入c:\python39\lib\site-packages目录，手动删除所有名称以~开头的破损包文件夹
• 先安装wheel依赖，再安装FastAPI全量包：

  py -3.10 -m pip install wheel
  py -3.10 -m pip install fastapi[all]
  

• 可选隔离安装方案：如果全局环境冲突过多，使用虚拟环境安装：

  # 创建虚拟环境
  py -3.10 -m venv fastapi-env
  # PowerShell环境激活虚拟环境
  .\fastapi-env\Scripts\Activate.ps1
  # CMD环境激活虚拟环境
  fastapi-env\Scripts\activate.bat
  # 激活后安装依赖
  pip install wheel
  pip install fastapi[all]
  

内容的提问来源于stack exchange，提问作者Obinna Okeke