Isn't that the distinction between repr() and str()? That repr() is generally (to a greater extent) meant to return eval()-able code, while str() is just something nice to look at.
I don't think the # of pages it outputs should really matter, if the thing you are printing really is that big. It won't be much bigger than printing big lists or dicts, and we happily let those cause the terminal to scroll for minutes at a time if we accidentally print them. The default behavior (e.g. when you print() it or string-interpolate it) would still give you something short and nice to look at. Presumably when someone called repr() instead of str(), he was hoping for some sort of eval()-able code snippet.
On Tue, Apr 30, 2013 at 6:21 PM, Guido van Rossum firstname.lastname@example.org wrote:
But do you really want it to print the entire parse tree even if it represents several pages of code?
On Tue, Apr 30, 2013 at 6:12 PM, Haoyi Li email@example.com wrote:
Wouldn't it be nice if this
import ast print repr(ast.parse("(1 + 1)").body.value)
<_ast.BinOp object at 0x0000000001E94B38>
printed something more useful?
print repr(ast.parse("(1 + 1)").body.value) BinOp(left=Num(n=1), op=Add(), right=Num(n=1))
I've been doing some work on macropy, which uses the ast.* classes extensively, and it's annoying that we have to resort to dirty-tricks like monkey-patching the AST classes (for CPython 2.7) or even monkey-patching __builtin__.repr (to get it working on PyPy) just to get
eval(repr(my_ast)) == my_ast
to hold true. And a perfectly good solution already exists in the ast.dump() method, too! (It would also be nice if "==" did a structural comparison on the ast.* classes too, but that's a different issue).
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