title: Creating a basic calculator in python
body: <p>This is what I have so far: </p>
  
  <pre><code>import sys
  
  first = float(sys.argv[1])
  second = str(sys.argv[2])
  third = float(sys.argv[3])
  
  if second == "+":
    print first + third
  elif second == "-":
    print first - third
  elif second == "*":
    print first * third
  elif second == "/":
    print first / third
  elif second == "^":
    print first ** third
  else:
    print "Invalid Operator"
  </code></pre>
  
  <p>The first and third arguments are supposed to be double floating point numbers. I wasn't sure how the operator is supposed to be represented, so I just named it "second" and set it as a string. I'm confused as to how I'm supposed to actually get the calculations. Are my if/elif/else statements wrong? Am I supposed to use "print" or "return" for actual calculations to be made?</p>
  
  <p>This is an example of a test file:</p>
  
  <pre><code> def test_add(self):
      output = self.runScript("simple_calc.py", "1", "+", "1")
      result = float(output)
      self.assertAlmostEqual(2.0, result, places=10)
      output = self.runScript("simple_calc.py", "-1", "+", "1")
      result = float(output)
      self.assertAlmostEqual(0.0, result, places=10)
      output = self.runScript("simple_calc.py", "1.0", "+", "-1.0")
      result = float(output)
      self.assertAlmostEqual(0.0, result, places=10)
  </code></pre>