运行命令brew install pip3，结果界面一直卡在Updating Homebrew…上

解决办法是替换brew源：
替换brew.git:
cd "$(brew --repo)"
git remote set-url origin https://mirrors.ustc.edu.cn/brew.git

替换homebrew-core.git:
cd "$(brew --repo)/Library/Taps/homebrew/homebrew-core"
git remote set-url origin https://mirrors.ustc.edu.cn/homebrew-core.git

重置brew.git:
cd "$(brew --repo)"
git remote set-url origin https://github.com/Homebrew/brew.git

重置homebrew-core.git:
cd "$(brew --repo)/Library/Taps/homebrew/homebrew-core"
git remote set-url origin https://github.com/Homebrew/homebrew-core.git

查看当前Homebrew 镜像源

# brew.git镜像源
git -C "$(brew --repo)" remote -v

# homebrew-core.git镜像源
git -C "$(brew --repo homebrew/core)" remote -v

# homebrew-cask.git镜像源
git -C "$(brew --repo homebrew/cask)" remote -v 

国内镜像地址

• 科大: https://mirrors.ustc.edu.cn
• 阿里: https://mirrors.aliyun.com/homebrew/

科大真香实例：

git -C "$(brew --repo)" remote set-url origin https://mirrors.ustc.edu.cn/brew.git

git -C "$(brew --repo homebrew/core)" remote set-url origin https://mirrors.ustc.edu.cn/homebrew-core.git

git -C "$(brew --repo homebrew/cask)" remote set-url origin https://mirrors.ustc.edu.cn/homebrew-cask.git

if [ $SHELL = "/bin/bash" ] # 如果你的是bash
then 
    echo 'export HOMEBREW_BOTTLE_DOMAIN=https://mirrors.ustc.edu.cn/homebrew-bottles/' >> ~/.bash_profile
    source ~/.bash_profile
elif [ $SHELL = "/bin/zsh" ] # 如果用的shell 是zsh 的话
then
    echo 'export HOMEBREW_BOTTLE_DOMAIN=https://mirrors.ustc.edu.cn/homebrew-bottles/' >> ~/.zshrc
    source ~/.zshrc
fi

brew update

如果需要恢复原有镜像源的话（国内镜像源突然不能用了或版本不够新）

git -C "$(brew --repo)" remote set-url origin https://github.com/Homebrew/brew.git

git -C "$(brew --repo homebrew/core)" remote set-url origin https://github.com/Homebrew/homebrew-core.git

git -C "$(brew --repo homebrew/cask)" remote set-url origin https://github.com/Homebrew/homebrew-cask.git

# 找到 ~/.bash_profile 或者 ~/.zshrc 中的HOMEBREW_BOTTLE_DOMAIN 一行删除

brew update

如果可以了下面的就不用看了

如果不行的话可以依次尝试以下命令

brew doctor
brew update-reset
brew update