Take user input (#2)

* Take user input

Although this is meant to be a `module`, many people would prefer to
run the program directly. So, I have added the functionality to ask
the user for a valid chemical structure.

I have also added a `help` command to get usage information.

TODO: Maybe add more examples to the help() function?

* Changed `comp_struct` to `compound_struct`

Used strip() instead of .lstrip().rstrip()

* Remove `help()` and use Namer.__doc__

Author: jithin-renji

Carbonpy.py

@@ -10,6 +10,18 @@
 
 
 class Namer(object):  # IUPAC Names for now only
+
+    """
+    Bonds are represented as follows:
+        -   :   Single bond
+        =   :   Double bond
+        ~   :   Triple bond
+
+    Examples:
+        CH~CH
+        CH~C-C~C-CH=C=C=CH2
+    """
+
     symbol = '\u2261'  # The triple bond symbol ≡
     subscripts = str.maketrans("0123456789", "₀₁₂₃₄₅₆₇₈₉")  # Subscripts for molecular and structural formula
 
@@ -169,18 +181,24 @@ class ValencyError(Exception):
 
 multipl_suffixes = {2: "di", 3: "tri", 4: "tetra", 5: "penta", 6: "hexa", 7: "hepta", 8: "octa", 9: "nona"}
 
-compound1 = Namer('CH3-C~C-CH3')
-compound2 = Namer('CH~CH')
-compound3 = Namer('CH~C-C~C-CH=C=C=CH2')
-compound4 = Namer('CH4')
-compound5 = Namer('CH2=CH-CH=CH-CH=CH2')
-compound6 = Namer('CH2=CH2')
-compound7 = Namer('CH~C-CH=CH2')
-
-print(f"{compound1}\n{compound1.molecular_formula()}\n{compound1.analyser()}\n")
-print(f"{compound2}\n{compound2.molecular_formula()}\n{compound2.analyser()}\n")
-print(f"{compound3}\n{compound3.molecular_formula()}\n{compound3.analyser()}\n")
-print(f"{compound4}\n{compound4.molecular_formula()}\n{compound4.analyser()}\n")
-print(f"{compound5}\n{compound5.molecular_formula()}\n{compound5.analyser()}\n")
-print(f"{compound6}\n{compound6.molecular_formula()}\n{compound6.analyser()}\n")
-print(f"{compound7}\n{compound7.molecular_formula()}\n{compound7.analyser()}\n")
+def main():
+    print("Type `/help` to get usage information.")
+    
+    while True:
+        try:
+            compound_struct = input("Condensed structure > ")
+            if compound_struct.strip() == "/help":
+                print(Namer.__doc__)
+            else:
+                compound = Namer(compound_struct.strip())
+                print(f"\n{compound}\n{compound.molecular_formula()}\n{compound.analyser()}\n")
+
+        except EOFError:
+            print("\nExiting...")
+            quit()
+
+        except Exception:
+            print("Invalid input!")
+
+if __name__ == "__main__":
+    main()