Python调用file.close()后文件仍被占用，邮件附件发送后移动文件报错求助

核心原因 #

邮件发送后，附件文件的句柄未被完全释放（比如SMTP连接未关闭、文件流未关闭），导致系统仍锁定该文件，无法执行移动操作。

解决方案 #

1. 确保文件流被正确关闭 #

添加附件时，必须用with语句打开文件，保证文件自动关闭，避免手动关闭遗漏：

with open(attachment_path, "rb") as attachment_file:
    part = MIMEBase('application', 'octet-stream')
    part.set_payload(attachment_file.read())
    encoders.encode_base64(part)
    part.add_header('Content-Disposition', f"attachment; filename={os.path.basename(attachment_path)}")
    msg.attach(part)

2. 显式关闭SMTP连接 #

发送邮件后，必须调用server.quit()或通过with语句管理SMTP连接，确保连接资源完全释放：

with smtplib.SMTP(smtp_server, smtp_port) as server:
    server.starttls()
    server.login(smtp_user, smtp_pass)
    server.sendmail(sender_email, receiver_email, msg.as_string())
    # 显式退出，强制释放所有关联资源
    server.quit()

3. 排查其他占用进程 #

如果以上操作仍无效，检查是否有杀毒软件、文件预览工具等第三方进程在访问目标文件，临时关闭这类工具后重试。

4. 临时延迟方案（不推荐，仅作应急） #

若无法定位资源泄漏点，可在邮件发送完成后添加短暂延迟，给系统足够时间释放文件：

import time
# 邮件发送完成后
time.sleep(1)
shutil.move(attachment_path, archive_path)

完整示例代码 #

import smtplib
import os
import shutil
import time
from email.mime.multipart import MIMEMultipart
from email.mime.base import MIMEBase
from email import encoders

# 配置信息
smtp_server = "smtp.example.com"
smtp_port = 587
smtp_user = "your_email@example.com"
smtp_pass = "your_password"
sender_email = "your_email@example.com"
receiver_email = "target@example.com"
attachment_path = "test.txt"
archive_dir = "archive"
archived_filename = f"test_{time.strftime('%Y%m%d_%H%M%S')}.txt"
archive_path = os.path.join(archive_dir, archived_filename)

# 创建归档目录（如果不存在）
os.makedirs(archive_dir, exist_ok=True)

# 构建邮件
msg = MIMEMultipart()
msg['From'] = sender_email
msg['To'] = receiver_email
msg['Subject'] = "Test Email with Attachment"

# 添加附件（用with保证文件关闭）
with open(attachment_path, "rb") as attachment_file:
    part = MIMEBase('application', 'octet-stream')
    part.set_payload(attachment_file.read())
    encoders.encode_base64(part)
    part.add_header('Content-Disposition', f"attachment; filename={os.path.basename(attachment_path)}")
    msg.attach(part)

# 发送邮件并关闭连接
with smtplib.SMTP(smtp_server, smtp_port) as server:
    server.starttls()
    server.login(smtp_user, smtp_pass)
    server.sendmail(sender_email, receiver_email, msg.as_string())
    server.quit()

# 移动文件
shutil.move(attachment_path, archive_path)

内容的提问来源于stack exchange，提问作者kashif ashraf