Zbyszek, I just looked at [1] and I disagree that the environment variable should have higher precedence. In fact, I believe it should have lower precedence, and should be used as a fallback.

[1]: http://bugs.python.org/file23241/patch1.1.diff

Reason? Imagine a program is launched, and thus it has COLUMNS set to some value. While the program is running, the user resizes the terminal. I believe (though I have not tested) that the envvar will keep the old value, and this function would return wrong dimensions.

In my opinion, the system-specific code (termios/windll) should be tried first, and then the envvars (as fallback). If all else fails, maybe it would be better to return (None, None) and let the caller of this function handle that.