pip 报错

一、 No module named pip

如果在执行pip install --upgrade pip命令提示更新失败或是警告，再次使用pip提示“ModuleNotFoundError: No module named 'pip' ”错误；

1 执行第一条命令：

python -m ensurepip

2 执行第二条命令：

python -m pip install --upgrade pip

参考

二 ipython 安装和更新

pip install ipython

pip install --upgrade ipython

pip install --upgrade pip

不管是用pip装什么模块，前面都尽量不要加sudo，

三  Failed to start the Kernel.

Jupyter notebook中使用Markdown画流程图

试图安装nb-mermaid结果把Jupyter notebook搞挂了，kernal启动不了，

 是因为nb-mermaid把ipython给降级了。通过（pip install --upgrade ipython）修复Jupyter notebook。

参考

Failed to start the Kernel. 
AttributeError: module 'collections' has no attribute 'MutableMapping'. 
View Jupyter log for further details.

ERROR: pip's dependency resolver does not currently take into account all the packages that are installed. This behaviour is the source of the following dependency conflicts.
ipykernel 6.11.0 requires ipython>=7.23.1, but you have ipython 3.2.3 which is incompatible.