Re: Re: Guido's new method definition idea
Russ P. wrote: Python already uses shorthand extensively. How about "def"? For people who are so worried about self-explanatory symbols, what the heck does that stand for? Default? Defeat? Defect? Defunct? Defer? I think the difference here is that those other abbreviations are mostly fairly standard. The "def" keyword is the same in Ruby, and similar enough to "define" or "defun" in Scheme or LISP. The "!=" operator is pretty much standard across nearly all languages. What is being proposed with "$" here though, would be different from how it is used anywhere else and would be confusing. Moreover, I especially don't like proposing to eliminate as well in this instance the "dot notation", which is standard in nearly all object oriented languages. Using something as a substitute for "self" is one thing, and you can mostly use what you like there now, as "self" is more a convention than a requirement. But the "dot" that belongs there is critical to understanding, you can't hide that to save one keystroke. Getting back to Guido's suggestion, though, I think it makes some sense. Being new to Python, I did find myself occasionally forgetting "self" in instance methods. But, I also thought the requirement to include it was helpful in reminding me what was really going on there, that I was creating an instance method which was really a function that wouldn't actually be created until the instance was initiated. I tend to think this may be clearer though using the dot notation rather than passing the instance variable as a parameter. I'm not sure though whether allowing both syntaxes would make things more or less confusing. It might actually be helpful in some respects for newcomers to realize that self.method(arg) is somewhat the same as method(self, arg). Perhaps I'm wrong on this, I don't fully understand yet what is going on under the hood, but it seems to me that that would be part of the glue that allows Python to be so multi-paradigm; much of the difference between OOP and procedural or functional is just different syntax for the same thing. -- http://mail.python.org/mailman/listinfo/python-list
Re: Re: Rich Comparisons Gotcha
James Stroud wrote:
Rasmus
Fogh wrote:
Current behaviour is both inconsistent and counterintuitive, as these
examples show.
x = float('NaN')
x == x
False
Perhaps this should raise an exception? I think the problem is not
with comparisons in general but with the fact that nan is type float:
py> type(float('NaN'))
No float can be equal to nan, but nan is a float. How can something be
not a number and a float at the same time? The illogicality of nan's
type creates the possibility for the illogical results of comparisons
to nan including comparing nan to itself.
I initially thought that looked like a bug to me. But, this is
apparently standard behavior required for "NaN". I'm only using
Wikipedia as a reference here, but about 80% of the way down, under
"standard operations":
http://en.wikipedia.org/wiki/IEEE_754-1985
"Comparison operations. NaN is treated specially in that NaN=NaN always
returns false."
Presumably since floating point calculations return "NaN" for some
operations, and one "Nan" is usually not equal to another, this is the
required behavior. So not a Python issue (though understandably a bit
confusing).
The array issue seems to be with one 3rd party library, and one can
choose to use or not use their library, to ask them to change it, or
even to decide to override their == operator, if one doesn't like the
way it is designed.
--
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Beginner trying to understand functions.
simonh write:
In my attempt to learn Python I'm writing a small (useless) program to
help me understand the various concepts. I'm going to add to this as I
learn to serve as a single place to see how something works,
hopefully. Here is the first approach:
name = input('Please enter your name: ')
print('Hello', name)
while True:
try:
age = int(input('Please enter your age: '))
break
except ValueError:
print('That was not a valid number. Please try again.')
permitted = list(range(18, 31))
if age in permitted:
print('Come on in!')
elif age < min(permitted):
print('Sorry, too young.')
elif age > max(permitted):
print('Sorry, too old.')
input('Press any key to exit.')
That works fine. Then I've tried to use functions instead. The first
two work fine, the third fails:
def getName():
name = input('Please enter your name: ')
print('Hello', name)
def getAge():
while True:
try:
age = int(input('Please enter your age: '))
break
except ValueError:
print('That was not a valid number. Please try again.')
def checkAge():
permitted = list(range(18, 31))
if age in permitted:
print('Come on in!')
elif age < min(permitted):
print('Sorry, too young.')
elif age > max(permitted):
print('Sorry, too old.')
getName()
getAge()
checkAge()
I get this error message: NameError: global name 'age' is not
defined.
I'm stuck, can someone help? Thanks.
You are running into Python's scoping rules. Variables in Python are not
global by default, they are local to their scope. Each function has it's
own scope (but blocks like if: and while: don't.) So your variable "age"
only exists in
getage(). It doesn't exist in checkage(). You could simply add a
"global age" statement to getAge() before you first use the age
variable, and that will likely work.
Or, rather than declare it global, you might want to have getage()
return a value, and then pass it to checkage () as a function parameter.
Add a "return age" statement to getage() before "break". Then, for your def:
def checkage(age):
And then when calling:
A=getAge()
checkAge(A)
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Re: Re: Python is slow
cm_gui wrote: You guys are living in denial. Python is SLOW, especially for web apps. Instead of getting mad, why don't get together and come up with a faster VM/interpreter? The emperor doesn't like to be told he is not wearing any clothes? O The one in denial is the one without any evidence to back his assertions. as someone once said, "In God we Trust. All others must have data." For example, the most recent benchmarks from The Computer Language Benchmark Game: http://shootout.alioth.debian.org/u64/benchmark.php?test=all&lang=al http://shootout.alioth.debian.org/u32/benchmark.php?test=all&lang=all http://shootout.alioth.debian.org/gp4/benchmark.php?test=all&lang=all On Gentoo on a Pentium 4 for example: mean 07.10 Python Psyco 19.34 Lua 23.00 Python 28.27 Perl 30.00 PHP 66.28 Javascript SpiderMonkey 75.12 Ruby I have no idea about Zope, but if that's slow, go complain to the devlopers of Zope. The Python interpreter is one of the fastest for a dynamically interpreted language. And Psyco is competitive with many other JIT compilers. I would think someone who has been obsessing about the speed of Python since May, and especially interested in a Python "VM" would have learned by now about Psyco? -- http://mail.python.org/mailman/listinfo/python-list
