Python: Using ASCII values of arithmetic operators to perform the operation

Question

I have to perform a certain arithmetic operation between decimal numbers. The operations can be 'add', 'subtract' or 'multiply', and the desired operation will be passed in to our function along with the numbers. The way I want to do this is that I want to store the ASCII values of the operations '+', '-' and '*' and then somehow use that to perform the operation between the two numbers.

def (a, b, op):
  dict{'add':ord('+'), 'subtract':ord('-'), 'multiply':ord('*')}
  return a dict[op] b # this statement does not work

Is there a way to achieve something like that in python ?

I know one alternative is to use:

from operator import add,sub,mul

and then use the imported values in the hash instead, but for this question I am interested in finding out if its possible to do it the way I asked in the original question. Thanks !

ZdaR · Accepted Answer · 2015-04-21 08:52:24Z

1

Yes there is an eval() function in python which takes string as input and returns the output , so you slightly need to change the approach, eval() is generally used as :

print eval("2 + 3")
>>> 5

So the new code looks something like :

def evaluate(a, b, op):
    dict = {'add':'+', 'subtract':'-', 'multiply':'*'}
    return eval(str(a)+ dict[op] +str(b))

print evaluate(2,3,"add")
>>> 5

answered Apr 21, 2015 at 8:52

ZdaR

23.1k7 gold badges71 silver badges90 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Frédéric Hamidi Over a year ago

Be sure to read Is Using eval In Python A Bad Practice?, though.

ZdaR Over a year ago

Yeah I know, But it is the demand of the question , better way would be to use a switch case or some other neat approach but I didn't want to change the intent of the question so made minimal changes to make it work , thanks for the insight, appreciated :)

user1907906 · Accepted Answer · 2015-04-21 08:47:01Z

1

No, this

a dict[op] b

is not valid Python.

Use the functions from operator.

answered Apr 21, 2015 at 8:47

user1907906

Collectives™ on Stack Overflow

Python: Using ASCII values of arithmetic operators to perform the operation

2 Answers 2

2 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related