On 7/11/10 10:48 AM, wheres pythonmonks wrote: > I'm an old Perl-hacker, and am trying to Dive in Python. I have some > easy issues (Python 2.6) > which probably can be answered in two seconds: > > 1. Why is it that I cannot use print in booleans?? e.g.: >>>> True and print "It is true!"
Because print is a statement. Statements have to start lines. If you want to do this, use a function-- in Python 2.6 either via "from __future__ import print_function" or writing your own, even if its just a very thing wrapper around the print statement. > 2. How can I write a function, "def swap(x,y):..." so that "x = 3; y > = 7; swap(x,y);" given x=7,y=3?? > (I want to use Perl's Ref "\" operator, or C's &). > (And if I cannot do this [other than creating an Int class], is this > behavior limited to strings, > tuples, and numbers) You can't do that*. Its not limited to any certain type of objects. You can't manipulate calling scopes: if you really want to do that sort of explicit namespace mangling, use dictionaries (or objects, really) as the namespace to mangle and pass them around. > 3. Why might one want to store "strings" as "objects" in numpy > arrays? (Maybe they wouldn't)? I don't use numpy. No idea. > 4. Is there a way for me to make some function-definitions explicitly > module-local? In what sense? If you prepend them with an underscore, the function won't be imported with "from x import *". You can also explicitly control what is imported in that way with a module-level __all__ attribute. Now that won't stop someone from doing "import x" and "x._your_private_function" but Python doesn't believe in enforicng restrictions. > (Actually related to Q3 below: Is there a way to create an anonymous scope?) No. You can create a limited anonymous function with lambda, but note it takes only an expression-- no statements in it. > 5. Is there a way for me to introduce a indention-scoped variables in python? > See for example: http://evanjones.ca/python-pitfall-scope.html No. Python only has three scopes historically; local, global, and builtin. Then post-2.2(ish, I forget) limited nested scoping -- but only with nested functions, and you can't (until Python 3) re-bind variables in outer scopes (though you can modify them if they are mutable objects). Python's scoping is very basic (we generally think this is a good thing; others are never happy with it) and is not fully lexical scoped. > 6. Is there a Python Checker that enforces Strunk and White and is > bad English grammar anti-python? (Only half joking) > http://www.python.org/dev/peps/pep-0008/ Check out pylint and/or pychecker, which do various style-based checking. If you're asking for something else, I can't pierce your sarcasm to figure out what. -- Stephen Hansen ... Also: Ixokai ... Mail: me+list/python (AT) ixokai (DOT) io ... Blog: http://meh.ixokai.io/ * Yes, I know its actually possible, to manipulate outer/calling scopes with frame hacking. This is dangerous / bad / an implementation detail that one should not rely on or use, generally speaking. If you need to do this you're writing Java or Perl or C in Python, instead of writing Python in Python, so are probably doing all kinds of things that are slow / bad / dangerous / just not taking advantage of Python's strengths.
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