Bug in smtplib example

[MordechaiFast]

Documentation

The example code is meant to demonstrate sending a multi-line message. It does not do that; the lines get contracted into one.

This can be fixed by adding a newline character to the end of the line when it is added to the message string:

msg += line + '\n'

BTW, why not use PEP8 compliant names, f-strings, and context managers? Why make things complicated with a .strip() call? Why make it that blank lines in the message are like pressing send?

import smtplib


from_addr = input("From: ")
to_addrs  = input("To: ").split()
print("Enter message, end with ^D (Unix) or ^Z (Windows):")

# Add the From: and To: headers at the start!
msg = f"From: {from_addr}\r\nTo: {', '.join(to_addrs)}\r\n\r\n"
while True:
    try:
        line = input()
    except EOFError:
        break
    msg += line + '\n'

print("Message length is", len(msg))

with smtplib.SMTP('localhost') as server:
    server.set_debuglevel(1)
    server.sendmail(from_addr, to_addrs, msg)

Linked PRs

• gh-120662: improve smtplib example #120668
• [3.13] gh-120662: Improve smtplib example (GH-120668) #120681
• [3.12] gh-120662: Improve smtplib example (GH-120668) #120682

[hugovk]

Please can you link to the relevant page?

[terryjreedy]

The proper idiom would be to make an initialized list of lines, append further lines, and join with '\r\n' when complete.

    lines = [f"From: {from_addr}", "To: {', '.join(to_addrs)}", ""]
...
        lines.append(line)
...
    msg = '\r\n'.join(lines)

[picnixz]

BTW, why not use PEP8 compliant names, f-strings, and context managers?

Well... PEP 8 is a suggestion, not a requirement so it can't force people to follow it. For the rest, it's probably because at the time when it was written, f-strings and context managers did not exist and the code has not been updated since then.

Why make things complicated with a .strip() call?

To ensure that you don't have whitespaces before and after in the list of mails to send to, just before the split() call (and to avoid having an empty address).

Why make it that blank lines in the message are like pressing send?

that's a good question; I think it was assumed that you only want to send a single paragraph (though I agree it's not really a good idea since you could just end the message with CTRL+D).

---

I'll make a PR to improve the example. @terryjreedy May I shamefully take your idiom?

By the way Hugo, the page is https://docs.python.org/3/library/smtplib.html#smtp-example.

[picnixz]

I think this one can now be closed @hugovk

[terryjreedy]

@picnixz (" May I shamefully take your idiom?") Yes! I am delighted to wake up and find my suggestion implemented and merged.