Python 3's print() annoys me (although maybe it shouldn't)

November 19, 2012

One of a number of changes in Python 3 that I have a visceral unhappy reaction to is the replacement of the print statement by the print() function. On the one hand I sort of understand the 'computer science' perspective on changing it to a function; it moves Python's explicit statements closer to being purely intrinsic language operators. On the other hand, I just don't like it.

I think that part of the reason I don't like it is that it remains more or less magic while hiding that magic. When print was a statement, it was clear that it was pretty unusual and special. Turning print() into a function does not really make it any less magical (or central), but it sort of pretends otherwise in my eyes; the magic is now hidden behind a function call. Part of this feeling probably comes because print() is a built-in function, which makes it specially privileged; I'd consider sys.print() to be less magical (although more stupid; printing things is a pretty common and important operation, so short names for it matter).

On a pragmatic level, though, I'm clearly wrong; Python 3 print() is significantly less magical than Python 2 print, at least in CPython. CPython 2 has special bytecodes for printing things and print compiles down to them, while in Python 3 uses of print() compile to ordinary (global) function calls (and you can even redefine print() yourself if you want to be perverse). The arguments and special behaviors are also more regular and more easily discoverable (as a function, print() has in-Python documentation that you can see with help()).

(That print() is a real function opens up heavy use of print() to various sorts of the usual optimizations, and means that it's intrinsically somewhat slower than the Python 2 version since it necessarily involves a function name lookup and a function call. It's unlikely that this will matter to any real code, but you never know.)

PS: I know, I know. Even Python 2 has plenty of magical functions in the global namespace, things like type() or str(). I don't claim that my annoyance at print() is rational and I probably wouldn't be annoyed if Python had always had a print() function. Which implies that part of my annoyance may be due to what I see as a basically pointless renaming of a builtin to a function, one that forces a whole bunch of noisy code changes for no really compelling reason. (There is an entire rant about language changes without strong reasons that could go here.)

Also, I just tend to think that print reads better because it stands out more than yet another function call.

Sidebar: why C's printf() doesn't irritate me similarly

The simple version is that printf() is clearly a library function. A large part of the reason that this works in C and doesn't work in Python is namespaces, in that Python has them and C doesn't. In C everyone can dump functions into what in Python is the global namespace; in Python, modules cannot do this, which makes builtin names like print() special. Another reason this works in C is that producing output is clearly out of scope of the core C language, which is very limited and confined (it doesn't even have dynamic memory allocation).


Written on 19 November 2012.
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Last modified: Mon Nov 19 02:39:11 2012
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