[docs] [issue35783] incorrect example of fetching messages in imaplib documentation

[Макс Вернер]

New submission from Макс Вернер <mvarnar at gmail.com>:

An example of fetching messages from the mailbox given in "IMAP4 Example" section is incorrect:

typ, data = M.fetch(num, '(RFC822)')
print('Message %s\n%s\n' % (num, data[0][1]))

"fetch" may return server data that was not requested (see "7.4.2.  FETCH Response" section of RFC 3501). In that case "data[0][1]" won't return what user expects.
This is a bad example, that many people repeat and advise to other developers:
https://stackoverflow.com/questions/13210737/get-only-new-emails-imaplib-and-python
https://gist.github.com/robulouski/7441883
https://stackoverflow.com/questions/51098962/check-if-email-inbox-is-empty-imaplib-python3
https://stackoverflow.com/questions/21116498/imaplib-not-getting-all-emails-in-folder
https://stackoverflow.com/questions/2230037/how-to-fetch-an-email-body-using-imaplib-in-python

I guess, this peculiarity should be clarified in the documentation. I offer to mark this fetching method is not safe and requests careful fetch result parsing.

----------
assignee: docs at python
components: Documentation, email
messages: 334048
nosy: barry, docs at python, r.david.murray, Макс Вернер
priority: normal
severity: normal
status: open
title: incorrect example of fetching messages in imaplib documentation
type: enhancement
versions: Python 2.7, Python 3.5, Python 3.6, Python 3.7, Python 3.8

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<https://bugs.python.org/issue35783>
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