Merge pull request geekcomputers#164 from shreydan/master

added calculator.py

Author: geekcomputers

README.md

@@ -55,4 +55,4 @@ In the scripts the comments etc are lined up correctly when they are viewed in [
 
 - `timymodule.py` - A great alternative to Pythons 'timeit' module and easier to use.
 
-
+- `calculator.py` - Uses Python's eval() function to implement a calculator.

calculator.py

@@ -0,0 +1,58 @@
+"""
+Written by: Shreyas Daniel - github.com/shreydan
+Description: Uses Pythons eval() function 
+             as a way to implement calculator
+
+Functions available:
+
++ : addition
+- : subtraction
+* : multiplication
+/ : division
+% : percentage
+sine: sin(rad)
+cosine: cos(rad)
+tangent: tan(rad)
+square root: sqrt(n)
+pi: 3.141......
+"""
+
+import math
+
+def main():
+    
+    def calc(k):
+
+        functions = ['sin', 'cos', 'tan', 'sqrt', 'pi']    
+        
+        for i in functions:
+            if i in k.lower():
+                withmath = 'math.' + i
+                k = k.replace(i, withmath)
+        
+        try:
+            k = eval(k)
+        except ZeroDivisionError:
+            print ("Can't divide by 0")
+            exit()
+        except NameError:
+            print ("Invalid input")
+            exit()
+        
+        return k
+
+
+    print ("\nScientific Calculator\nEg: pi * sin(90) - sqrt(81)")
+
+    k = input("\nWhat is ")
+
+    k = k.replace(' ', '')
+    k = k.replace('^',' **')
+    k = k.replace('=', '')
+    k = k.replace('?', '')
+    k = k.replace('%', '/100')
+
+    print ("\n" + str(calc(k)))
+    
+if __name__ == "__main__":
+    main()