calculator.py: fixed mod error, new features and code changes

calculator.py

@@ -1,60 +1,69 @@
 """
-Written by: Shreyas Daniel - github.com/shreydan
-Description: Uses Pythons eval() function
-             as a way to implement calculator
-
+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......
+--------------------------------------------
+                         + : addition
+                         - : subtraction
+                         * : multiplication
+                         / : division
+                         % : percentage
+                         e : 2.718281...
+                        pi : 3.141592... 
+                      sine : sin(rad)
+                    cosine : cos(rad)
+                   tangent : tan(rad)
+                 remainder : XmodY
+               square root : sqrt(n)
+  round to nearest integer : round(n)
+convert degrees to radians : rad(deg)
 """
 
 import math
 import sys
 
 
-def main():
-
-    def calc(k):
-
-        functions = ['sin', 'cos', 'tan', 'sqrt', 'pi','mod']
+def calc(k):
+
+    k = k.replace(' ', '')
+    k = k.replace('^', '**')
+    k = k.replace('=', '')
+    k = k.replace('?', '')
+    k = k.replace('%', '/100')
+    k = k.replace('rad', 'radians')
+    k = k.replace('mod', '%')
 
-        for i in functions:
-            if i in k.lower():
-                withmath = 'math.' + i
-                k = k.replace(i, withmath)
+    functions = ['sin', 'cos', 'tan', 'sqrt', 'pi', 'radians', 'e'] 
 
-        try:
-            k = eval(k)
-        except ZeroDivisionError:
+    for i in functions:
+        if i in k.lower():
+            withmath = 'math.' + i
+            k = k.replace(i, withmath)
 
-            print("Can't divide by 0")
-            exit()
-        except NameError:
-            print('Invalid input')
-            exit()
+    try:
+        k = eval(k)
+    except ZeroDivisionError:
+        print("Can't divide by 0")
+        exit()
+    except NameError:
+        print('Invalid input')
+        exit()
+    except AttributeError:
+        print('Check usage method')
+        exit()
+
+    return k
 
-        return k
 
-    def result(k):
-        k = k.replace(' ', '')
-        k = k.replace('^', '**')
-        k = k.replace('=', '')
-        k = k.replace('?', '')
-        k = k.replace('%', '/100')
-	k = k.replace('mod', '%')
+def result(k):
+    print("\n" + str(calc(k)))
 
-        print("\n" + str(calc(k)))
 
-    print("\nScientific Calculator\nEg: pi * sin(90) - sqrt(81)\nEnter quit to exit")
+def main():
+
+    print("\nScientific Calculator\nEg: sin(rad(90)) + 50% * (sqrt(16)) + round(1.42^2) - 12mod3\nEnter quit to exit")
 
     if sys.version_info.major >= 3:
         while True: