如何在Python中切换目录执行脚本，解决树莓派pi_video_looper重启问题

Hey there! Let's break down your problems and fix them one by one.

1. How to Switch to a Specific Directory and Execute a Script in Python #

You’ve got a few solid options here—some simpler, some more robust:

Option 1: Use os.chdir() to Switch Globally #

This changes the working directory of your entire Python process before running the command:

import os

try:
    # Switch to the target directory
    os.chdir("/home/pi/pi_video_looper")
    # Execute the script with sudo
    os.system("sudo ./install.sh")
except FileNotFoundError:
    print("Error: Target directory doesn't exist!")
except Exception as e:
    print(f"An error occurred: {e}")

⚠️ Note: If your script runs other commands later, they’ll use this new directory unless you switch back manually.

Option 2: Use subprocess with cwd (Recommended) #

The subprocess module is more flexible than os.system—it lets you capture output, handle errors better, and specify the working directory without changing the global process state:

import subprocess

try:
    # Run the script in the target directory, with sudo
    result = subprocess.run(
        ["sudo", "./install.sh"],
        cwd="/home/pi/pi_video_looper",
        check=True,
        stdout=subprocess.PIPE,
        stderr=subprocess.PIPE,
        text=True
    )
    print("Script output:", result.stdout)
except subprocess.CalledProcessError as e:
    print(f"Script failed with error: {e.stderr}")
except FileNotFoundError:
    print("Error: Script or directory not found!")

The cwd parameter tells subprocess to run the command from that directory directly—no need to alter your Python script’s working directory.

Option 3: Shell Command with && #

If you prefer keeping it all in one shell command, you can chain the directory change and script execution:

import os

os.system("cd /home/pi/pi_video_looper && sudo ./install.sh")

This works because the cd and ./install.sh run in the same shell session—Python itself doesn’t switch directories, just the temporary shell instance that runs the command.

2. Automate NAS Mounting & Video Looper Restart on Raspberry Pi #

Manually stopping the looper, remounting, and restarting every reboot is a huge hassle. Let’s fix the root cause and automate this workflow:

Step 1: Fix Automatic NAS Mounting #

First, make sure your NAS mounts reliably on boot by updating /etc/fstab. Add a line like this (adjust values to match your NAS setup):

//your_nas_ip/your_share /mnt/nas cifs username=your_nas_user,password=your_nas_pass,vers=3.0,x-systemd.automount,x-systemd.mount-timeout=10 0 0

• x-systemd.automount: Makes systemd mount the share only when it’s accessed (avoids boot delays if the NAS is offline)
• x-systemd.mount-timeout=10: Times out after 10 seconds if the NAS isn’t reachable, so your Pi boot doesn’t get stuck

Test it with sudo mount -a—if it works, reboot to confirm it mounts automatically.

Step 2: Make Supervisor Depend on the NAS Mount #

Update your video_looper supervisor config (usually at /etc/supervisor/conf.d/video_looper.conf) to ensure it starts only after the NAS is mounted. Add these lines:

[program:video_looper]
command=/home/pi/pi_video_looper/start_looper.sh
directory=/home/pi/pi_video_looper
user=pi
autorestart=true
startsecs=5
environment=MOUNT_POINT="/mnt/nas"

Then create a wrapper script start_looper.sh to check if the NAS is mounted before starting the looper:

#!/bin/bash
MOUNT_POINT="/mnt/nas"

# Wait until the NAS is mounted
while ! mountpoint -q "$MOUNT_POINT"; do
    echo "Waiting for NAS mount..."
    sleep 2
done

# Start the video looper
./your_video_looper_executable

Make the script executable with chmod +x start_looper.sh.

Step 3: Allow Passwordless Sudo for Critical Commands #

To let your Python script run sudo commands without prompting for a password, edit the sudoers file:

sudo visudo

Add this line at the end:

pi ALL=(ALL) NOPASSWD: /usr/bin/mount, /usr/bin/supervisorctl, /home/pi/pi_video_looper/install.sh

This lets the pi user run those specific commands with sudo without entering a password—perfect for automation.

内容的提问来源于stack exchange，提问作者Elias Schuhmacher