"Steven D'Aprano" <st...@remove-this-cybersource.com.au> wrote in message
news:0182896d$0$8693$c3e8...@news.astraweb.com...
On Sun, 18 Jan 2009 11:11:45 +1000, elhombre wrote:
Hello, below is my first fragment of working python code. As you can see
it is very java like as that is all I know. Is this the right approach
to be taking?
You might find it very useful to read:
http://dirtsimple.org/2004/12/python-is-not-java.html
http://dirtsimple.org/2004/12/java-is-not-python-either.html
Should I be taking a different approach? Thanks in advance.
This is obviously a very minimal program, so I won't criticise you for
failing to do any error checking :-) However, I will make some broad
points:
* No getters and setters. Python takes a very permissive approach to
class attributes, taking the philosophy "we're all adults here". It's
easy to change a public attribute to a private attribute with a getter/
setter if you need to, so there's nothing to be gained by writing getters
for straight attribute access. It just makes things slow.
* Don't return error values, raise an exception. Setting up a
try...except block is really fast in Python, almost as fast as a pass
statement (according to my tests). Catching the exception itself is slow,
but most of the time you won't care about that.
Let me re-write your code in a more Pythonic way. This is not the only
way to do this, and it probably isn't the best way, but it may give you a
flavour for the way Python is usually written.
import sys
import operator
class Calculator():
dispatch = { # dispatch table mapping symbol to function
'+': operator.add,
'-': operator.sub,
'*': operator.mul,
'/': operator.truediv,
}
def __init__(self):
self.operator = sys.argv[1]
self.arg1 = int(sys.argv[2])
self.arg2 = int(sys.argv[3])
def calculate(self):
func = self.dispatch[self.operator]
return func(self.arg1, self.arg2)
if __name__ == '__main__':
# run this block only when running as a script, not
# when the module is being imported (say, for testing).
x = Calculator('+', 23, 42)
try:
y = x.calculate()
except KeyError:
print "Unrecognised operator '%s'" % x.operator
else:
print y
--
Steven
Excellent links. Thanks Steven !
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