[Python-3000] should rfc822 accept text io or binary io?

[Barry Warsaw]

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On Aug 17, 2007, at 1:22 PM, Martin v. Löwis wrote:

> A library implementing that in Python should certainly use bytes
> at the network (stream) side, and strings at the application side.
> Even though the format is human-readable, the protocol is byte- 
> oriented,
> not character-oriented.

I should point out that the email package does not really intend to  
operate from the wire endpoints.  For example, for sending a message  
over an smtp connection it expects that something like smtplib would  
properly transform \n to \r\n as required by RFC 2821.  It's a bit  
dicier on the input side since you could envision a milter or  
something taking an on-the-wire email representation from an smptd  
and parsing it into an internal representation.

As I'm working on the email package I'm realizing that classes like  
the parser and generator need to be stricter about how they interpret  
their input, and that both use cases are reasonable in many  
situations.  Sometimes you want the parser to accept strings, but  
bytes are not always unreasonable.  Similarly with generating  
output.  Internally though, I feel fairly strongly that an email  
message should be represented as strings, though sometimes (certainly  
for idempotency) you still need to carry around the charset (i.e.  
encoding).  Headers are an example of this.

The email package conflates 8-bit strings and bytes all over the  
place and I'm trying now to make its semantics much clearer.   
Ideally, the package would be well suited not only for wire-to-wire  
and all-internal uses, but also related domains like HTTP and other  
RFC 2822-like contexts.

- -Barry

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