A java hobbyist programmer learning python

[Chris Rebert]

On Sat, Jan 17, 2009 at 5:11 PM, elhombre <elhmbre at ozemail.com.au> 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?
> Should I be taking a different approach? Thanks in advance.
>
> import sys
>
> class Calculator():
>
>   def __init__(self):
>       self.operator = sys.argv[1]
>       self.arg1 = sys.argv[2]
>       self.arg2 = sys.argv[3]
>
>   def getOperator(self):
>       return sys.argv[1]
>
>   def getArg1(self):
>       return sys.argv[2]
>
>   def getArg2(self):
>       return sys.argv[3]

Delete the 3 Java-ish accessor methods; good Python style just uses
the attributes directly (i.e. self.operator instead of
self.getOperator()).

>
>   def calculate(self):
>       if self.getOperator() == '+' :
>           return int(self.getArg1()) + int(self.getArg2())
>       elif self.getOperator() == '*' :
>           return int(self.getArg1()) * int(self.getArg2())
>       elif self.getOperator() == '/' :
>           return int(self.getArg1()) / int(self.getArg2())
>       elif self.getOperator() == '-' :
>           return int(self.getArg1()) - int(self.getArg2())
>       else:
>           return 'Wrong argument supplied'

Rather than have a long if-elif-else chain like this, you can use a
dictionary with functions as values. For example:

def add(x, y):
    return x + y

def sub(x, y):
    return x - y

OPER2FUNC = {'+' : add, '-' : sub}
print OPER2FUNC['+'](3,4) #==> 7

You can use the same technique with the functions in the `operator`
module to significantly shorten your calculate() method.

Cheers,
Chris

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