[Python-Dev] Replacement for print in Python 3.0 (original) (raw)

Guido van Rossum guido at python.org
Tue Sep 6 16:21:09 CEST 2005

On 9/6/05, Nick Coghlan <ncoghlan at gmail.com> wrote:

I did a fair bit of tinkering with that on the weekend. Printing a sequence of strings is fine - it's the call to "map(str, seq)" that makes printing a sequence of non-strings uglier than it should be. Doing it that way also breaks the Python idiom of letting unicode remain as unicode.

Only of you insist on doing it in a single call. With an explicit for loop all is well.

However, one thing I eventually remembered was a discussion about a year ago regarding the possibility of allowing str.join and unicode.join to accept non-strings [1].

That discussion ended up leaving the join methods alone, because it is damn hard to do it without slowing down the common case where the sequence is all strings. I'm currently considering proposing a "joinany" method for str and unicode which accepts a sequence of arbitrary objects (I have a patch, but it needs unit tests and docs, and I'm uncomfortable with the amount of code duplication between the join and joinany methods).

Why not take an idea that Fredrik Lundh mentioned earlier, and have a built-in function named join() which takes a sequence and a string? joinany() is an ugly name.

But what's still missing is a use case analysis where you prove that the use case is common enough to require explicit support.

This becomes especially clear once "sorted" and "list.sort" are given as examples where the various keyword arguments do not change the basic invariant properties of the sorting operations - you start with a sequence, and you end up with essentially the same sequence, only in a different order. The keyword arguments simply control the precise meaning of "different order".

Thanks -- a very good example!

'printraw' is good - it makes it clear it is part of the same family as 'print' and 'printf', and explains succintly how it differs from the normal print function.

(Except that 'raw' could mean anything.)

Additionally, doing 'printraw' with 'printf' is a little tricky - the best I've come up with is "printf('%s'*3, a, b, c)".

Yeah, but often the real code you need to do is already written as

print("x =", x, "y =", y, "z =", z)

and that becomes more readable when you transform it to

printf("x = %s y = %s z = %s\n", x, y, z)

-- --Guido van Rossum (home page: http://www.python.org/~guido/)

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