[Python-Dev] RE: fileinput.py

Ka-Ping Yee ping@lfw.org
Fri, 5 Jan 2001 16:01:53 -0600 (CST)

On Fri, 5 Jan 2001, Thomas Wouters wrote:

> On Fri, Jan 05, 2001 at 03:46:10PM -0500, Tim Peters wrote:
> > That is, "<>" is usually used simply as an abbrevision for <STDIN>, and I
> > bet *most* Perl programmers don't even know "<>" is more general than that.
> Well, I can't say anything about *most* Perl programmers, but all Perl
> programmers I know (including me) know damned well what <> does, and use it
> frequently. And in all the ways: no arguments meaning <STDIN>, a list of
> files meaning open those files one at a time, using - to include stdin in
> that list, accessing the filename and linenumber, etc.

I was just about to chime in and say the same thing.  I don't even
program in Perl any more, and i still remember all the ways that <> works.

For text-processing scripts, it's unbeatable.  It does pretty much
exactly everything you want, and the idiom

    while (<>) {

is simple, quickly learned, frequently used, and instantly recognizable.

    import sys
    if len(sys.argv) > 1:
        file = open(sys.argv[1])
        file = sys.stdin
    while 1:
        line = file.readline()
        if not line:

is much more complex, harder to explain, harder to learn, and runs slower.

I have two separate suggestions:

    1.  Include 'sys' in builtins.  It's silly to have to 'import sys'
        just to be able to see sys.argv and sys.stdin.

    2.  Put fileinput.input() in sys.

With both, the while (<>) idiom becomes:

    for line in sys.input():

-- ?!ng

"This code is better than any code that doesn't work has any right to be."
    -- Roger Gregory, on Xanadu