CODEWITHSUNDEEP
pythonif-statement
David L.E
David L.E

Reputation: 105

How to write IF functions in Python when the condition requires the input to be a special character?

I'm trying to build a sample calculator in Python. It's expected output for calculate(2, 3, -) should be -1.

However, I have a hard time defining the operator.

if operator == +: will return a syntax error, but when I do if operator == '+': I need to write something like calcuate(3, 4, '+') to work.

Here are 

def calculate(x, y, operator):
    if operator == '+':
        print (x + y)
    elif operator == '-':
        print (x - y)
    elif operator == '*':
        print (x * y)
    elif operator == '/':
        print (x / y)

Is it possible for me to get rid of the required apostrophes?

Upvotes: 2

Views: 277

Answers (1)

DarrylG
DarrylG

Reputation: 17166

As the comments indicate you can not simply pass +, -, div.

Another option that would simplify your code is to use the operator module

Code refactoring using operator module

# We obtain operators we will use from operator module
from operator import add, sub, mul, pow
from operator import truediv as div

def calculator(x, y, op):
  " Calculator applies the passed-in operator to arguments "
  return op(x, y)

# Tests
print(calculator(5, 3, add))
print(calculator(5, 3, sub))
print(calculator(5, 3, mul))
print(calculator(5, 3, div))
print(calculator(5, 3, pow))

Using Your Original String Input

As @JLPeyret suggests, operators make it easier to use a dictionary for the logic for which operation to choose.

def calculator(x, y, op):
      " Calculator applies the passed-in operator to arguments "
    d = {'+', add,
         '-', sub,
         '*', mul,
         '/', div,
         '**', pow}
      return d[op](x, y)

# Tests
print(calculator(5, 3, '+'))
print(calculator(5, 3, '-'))
print(calculator(5, 3, '*'))
print(calculator(5, 3, '/'))
print(calculator(5, 3, '**'))

Outputs in both cases

8
2
15
1.6666666666666667
125

Upvotes: 2

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