Question

我的requirements.txt中有以下两个依赖项：

$ pip3 install elasticsearch==7.0.0 requests==2.21.0
Collecting elasticsearch==7.0.0
  Using cached https://files.pythonhosted.org/packages/a8/27/d3a9ecd9f8f972d99da98672d4766b9f62ef64c323c40bb5e2557e538ea3/elasticsearch-7.0.0-py2.py3-none-any.whl
Collecting requests==2.21.0
  Using cached https://files.pythonhosted.org/packages/7d/e3/20f3d364d6c8e5d2353c72a67778eb189176f08e873c9900e10c0287b84b/requests-2.21.0-py2.py3-none-any.whl
Collecting urllib3>=1.21.1 (from elasticsearch==7.0.0)
  Using cached https://files.pythonhosted.org/packages/39/ec/d93dfc69617a028915df914339ef66936ea976ef24fa62940fd86ba0326e/urllib3-1.25.2-py2.py3-none-any.whl
Collecting certifi>=2017.4.17 (from requests==2.21.0)
  Using cached https://files.pythonhosted.org/packages/60/75/f692a584e85b7eaba0e03827b3d51f45f571c2e793dd731e598828d380aa/certifi-2019.3.9-py2.py3-none-any.whl
Collecting chardet<3.1.0,>=3.0.2 (from requests==2.21.0)
  Using cached https://files.pythonhosted.org/packages/bc/a9/01ffebfb562e4274b6487b4bb1ddec7ca55ec7510b22e4c51f14098443b8/chardet-3.0.4-py2.py3-none-any.whl
Collecting idna<2.9,>=2.5 (from requests==2.21.0)
  Using cached https://files.pythonhosted.org/packages/14/2c/cd551d81dbe15200be1cf41cd03869a46fe7226e7450af7a6545bfc474c9/idna-2.8-py2.py3-none-any.whl
requests 2.21.0 has requirement urllib3<1.25,>=1.21.1, but you'll have urllib3 1.25.2 which is incompatible.
Installing collected packages: urllib3, elasticsearch, certifi, chardet, idna, requests
Successfully installed certifi-2019.3.9 chardet-3.0.4 elasticsearch-7.0.0 idna-2.8 requests-2.21.0 urllib3-1.25.2

我想了解以上输出中出现的警告：

requests 2.21.0 has requirement urllib3<1.25,>=1.21.1, but you'll have urllib3 1.25.2 which is incompatible.

为什么pip安装了urllib3 1.25.2？这似乎没有意义。所需的依赖项是：

elasticsearch==7.0.0要求urllib3>=1.21.1（source）
requests==2.21.0要求urllib3>=1.21.1,<1.25（source）

通过安装urllib3 1.24.3可以轻松满足这两个依赖关系。为什么pip3然后安装urllib3 1.25.2？难道不是根据可用需求确定正确的版本吗？

这是pip3中的错误，还是功能正常？

Answer 1

pip doesn’t have true dependency resolution现在，只是使用它为项目找到的第一个规范。

您可以使用constraints.txt添加urllib3==1.24.3文件，然后调用：

$ pip install -r requirements.txt -c contraints.txt

那样就可以了。更新需求时，请记住也要矛盾。

或者，您可以使用以下一种Python dependency managers：

请参阅pip用户指南和Requirements Files教程中的Constraints Files和Managing Application Dependencies部分。

pip3安装了一个版本的依赖项，该版本违反了需求说明符

1 个答案: