. Sm0kin'_Bull said unto the world upon 2005-02-19 16:15:
I want to make caculator program which enables me to
enter 2numbers and mathsmatics sign and calculates it.
I think this is too difficult for newbie like me...
Please input data
Number1:
Mathsmetics Sign:
Number2:
(Number1) (Sign) (Number2) = (Result)
I wrote this but, Error occurs
print "Please input data"
number1 = int(raw_input("\nNumber1: "))
sign = (raw_input("\nMathsmetics Sign: "))
number2 = int(raw_input("\nNumber2: "))
total = number1 sign number2
print number1, sign, number2, '=', total
please help me
Cheers! :)
Hi,
what are you expecting this line:
total = number1 sign number2
to do?
total = number1 sign number2
SyntaxError: invalid syntax
The Python interpreter reads the line and says 'Ah, total should equal
number1 -- hey, wait, what I am supposed to do with this other stuff
like sign?'
So, you've got to figure a way to tell the interpreter just how you
want these things combined.
Following the sort of approach you have started with, you've got some
integers and a mathematical operation sign, and you want to *eval*uate
their combination somehow. That suggests
eval('5 + 6')
11
So, this code will work (tested!):
<code>
print "Please input data"
number1 = raw_input("\nNumber1: ")
sign = raw_input("\nMathsmetics Sign: ")
number2 = raw_input("\nNumber2: ")
print eval(number1 + sign + number2)
</code>
<output>
IDLE 1.1
================================ RESTART
================================
Please input data
Number1: 42
Mathsmetics Sign: *
Number2: 100
4200
</output>
But, this isn't a very good approach, in my opinion. For one thing,
eval is dangerous.
I have an alternate suggestion. It uses several things which may be
new to you. And, as you know, I am no expert, so I make no claim this
is the *best* way. I do think it is better but think it likely that
someone else will post a better idea, still.
Anyway, take a look at this code and see if you can work it out. If
not, post again.
<tested code>
import operator
ops_dict = {'+': operator.add, '*' : operator.mul}
def perform_arithmetic():
print "Please input data"
number1 = int(raw_input("\nNumber1: "))
sign = raw_input("\nMathsmetics Sign: ")
number2 = int(raw_input("\nNumber2: "))
try:
result = ops_dict[sign](number1, number2)
except KeyError:
raise NotImplementedError, "I don't know the sign '%s'" %sign
# add output formatting logic as desired
return result
print perform_arithmetic()
<tested code>
Hope that helps,
Brian vdB
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