Hey Sam, I’ve run into this exact issue dozens of times with macOS’s system Python—let’s break down the most reliable fixes, ordered by how safe and sustainable they are:

1. Use the --user Flag (Quickest, Official Recommended Fix) #

This is the simplest way to bypass system permission locks, since it installs packages to your user-specific directory instead of the protected system Python folders. Just run this command:

pip install --user -r requirements.txt

The packages will land in ~/Library/Python/2.7/site-packages, which your account has full access to. Your Python script will automatically detect these packages when you run it normally.

2. Use sudo (Not Recommended, But Works for Global Installs) #

If you absolutely need packages installed globally (I’d strongly advise against this, since it can break macOS’s built-in tools that rely on system Python), you can run pip with admin privileges:

sudo pip install -r requirements.txt

You’ll be prompted for your Mac password. Again, this is risky—modifying system Python packages can cause unexpected behavior with macOS utilities, so only use this as a last resort.

3. Use a Virtual Environment (Best Long-Term Solution) #

Since Python 2.7 is no longer supported, using a virtual environment is the cleanest way to isolate your project’s dependencies and avoid permission issues entirely. Here’s how to set it up:

• First install virtualenv (using --user to skip permission hurdles):

  pip install --user virtualenv
  

• Navigate to your project directory:

  cd /path/to/your/project/folder
  

• Create a virtual environment named venv (you can name it anything):

  virtualenv venv
  

• Activate the virtual environment—you’ll see (venv) at the start of your terminal prompt when it’s active:

  source venv/bin/activate
  

• Now install your requirements—no permission issues here, since the environment is fully under your control:

  pip install -r requirements.txt
  

• When you’re done working, deactivate the environment with:

  deactivate
  

Why Modifying Folder Permissions Didn’t Work #

macOS has a security feature called System Integrity Protection (SIP) that locks down system directories like /Library/Python/2.7/site-packages. Even if you run chmod or chown on these folders, SIP will block write access—this is intentional to prevent accidental system damage, so manual permission changes won’t work here.

内容的提问来源于stack exchange，提问作者Sam