This article aims to solve the problem of abnormal display due to spaces in attachment file names when sending emails using Python. We will explore how to ensure that the receiver can correctly recognize and handle file names with spaces by correctly setting the Content-Disposition header, thereby avoiding problems with file name truncation or display of encoded characters.

When using the Python email library to send an email with an attachment, if the file name of the attachment contains spaces, the file name seen by the recipient may be truncated or displayed as other encoded characters. This is because the Content-Disposition header handles spaces in file names differently. Here's how to properly handle this situation.

Problem analysis

When the file name contains spaces, embed them directly in the Content-Disposition header. Some email clients may truncate the part after the spaces, resulting in an incomplete file name. For example, my attachment.pdf might be recognized as my. On the other hand, if you replace spaces with , although truncation can be avoided, the file name seen by the receiver will also be included, affecting the user experience.

solution

The key to solving this problem is to use quotes around the file name. By putting the filename in quotes, you explicitly tell the mail client that the entire string is part of the filename, thus handling whitespace correctly.

Sample code

In the email library, the Content-Disposition header can be set in the following ways:

 import smtplib
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
from email.mime.base import MIMEBase
from email import encoders
import os

def prepare_attachment(filepath):
    filename = os.path.basename(filepath)
    attachment = open(filepath, "rb")

    # instance of MIMEBase and named as p
    p = MIMEBase('application', 'octet-stream')

    # To change the payload into encoded form.
    p.set_payload((attachment).read())

    # encode into base64
    encoders.encode_base64(p)

    # Use quotes to enclose the file name p.add_header('Content-Disposition', 'attachment; filename="%s"' % filename)

    return p


classSender(object):

    def __init__(self, sender_email, sender_password, recipient_email, attachments):
        self.sender_email = sender_email
        self.sender_password = sender_password
        self.recipient_email = recipient_email
        self.attachments = attachments

    def send(self):
        msg = MIMEMultipart()
        msg['From'] = self.sender_email
        msg['To'] = self.recipient_email
        msg['Subject'] = "Attachment Test"

        msg.attach(MIMEText("This is a test email with attachments.", 'plain'))

        for attachment in self.attachments:
            p = prepare_attachment(attachment)
            msg.attach(p)

        try:
            s = smtplib.SMTP('smtp.gmail.com', 587)
            s.starttls()
            s.login(self.sender_email, self.sender_password)
            text = msg.as_string()
            s.sendmail(self.sender_email, self.recipient_email, text)
            s.quit()
            print("Email sent successfully!")
        except Exception as e:
            print(f"Error sending email: {e}")


# Example usage
if __name__ == '__main__':
    sender_email = "your_email@gmail.com" # Replace with your email address
    sender_password = "your_password" # Replace with your email password
    recipient_email = "recipient_email@example.com" # Replace with recipient's email address
    attachments = ["my attachment.pdf"] # Replace with the path to your attachment

    sender = Sender(sender_email, sender_password, recipient_email, attachments)
    sender.send()

In the above code, the key line is:

 p.add_header('Content-Disposition', 'attachment; filename="%s"' % filename)

Here, "%s" is used to enclose the filename variable to ensure that spaces in the file name are handled correctly.

Things to note

• Make sure the filename variable contains the full filename, including extension.
• If the file name contains quotes themselves, they need to be escaped to avoid parsing errors.
• Different email clients may handle the Content-Disposition header slightly differently, but using quotes usually solves most problems.

Summarize

By enclosing the file name in quotation marks in the Content-Disposition header, you can effectively solve the problem caused by spaces in the attachment file name, ensure that the recipient can correctly identify and process the attachment, and improve the user experience. It is important to pay attention to this when writing a Python application that sends emails to avoid potential problems.

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