feat: better try/except/else case

Author: Scott Archer-Nicholls

episodes/05-defensive_programming.md

@@ -34,11 +34,11 @@ Please look at the following code. Can you find the fundamental problem in this
 val = 1
 
 if val > 0:
-    print('Value: ', val, 'is positive.')
+    print('Value:', val, 'is positive.')
 elif val == 0:
-    print('Value: ', val, 'is zero.')
+    print('Value:', val, 'is zero.')
 else:
-    print('Value: ', val, 'is negative.')
+    print('Value:', val, 'is negative.')
 ```
 
 :::::::::::::::  solution
@@ -51,11 +51,11 @@ The test assumes that `val` is a number, and throws an uncontrolled error if it
 val = 'a'
 
 if val > 0:
-    print('Value: ', val, 'is positive.')
+    print('Value:', val, 'is positive.')
 elif val == 0:
-    print('Value: ', val, 'is zero.')
+    print('Value:', val, 'is zero.')
 else:
-    print('Value: ', val, 'is negative.')
+    print('Value:', val, 'is negative.')
 ```
 
 ```output
@@ -64,9 +64,9 @@ TypeError                                 Traceback (most recent call last)
 <ipython-input-2-99c0e25bf5e9> in <module>()
       1 def check_sign(val):
 ----> 2     if val > 0:
-      3         print('Value: ', val, 'is positive.')
+      3         print('Value:', val, 'is positive.')
       4     elif val == 0:
-      5         print('Value: ', val, 'is zero.')
+      5         print('Value:', val, 'is zero.')
 
 TypeError: '>' not supported between instances of 'str' and 'int'
 ```
@@ -81,11 +81,11 @@ To make things simpler, we will first write the test as a function:
 ```python
 def check_sign(val):
     if val > 0:
-        print('Value: ', val, 'is positive.')
+        print('Value:', val, 'is positive.')
     elif val == 0:
-        print('Value: ', val, 'is zero.')
+        print('Value:', val, 'is zero.')
     else:
-        print('Value: ', val, 'is negative.')
+        print('Value:', val, 'is negative.')
 ```
 
 Then wrap the function call in an `if` statement:
@@ -131,15 +131,19 @@ As with `if` statements, multiple `except` statements can be used, each with a d
 ```python
 try:
     check_sign(val)
+    reciprocal = 1/val
 except TypeError as err:
     print('Val is not a number')
     print('But our code does not crash anymore')
     print('The run-time error is:', err)
+except Exception as err:
+    print('Some error other than a TypeError occured')
+    print('But our code does not crash')
+    print('The run-time error is:', err)
 else:
-    print('The value provided to the check_sign function did not result in a TypeError')
+    print('The reciprocal of the value =', reciprocal)
 finally:
     print('release memory')
-    del(val)
 ```
 
 The typical use of the `finally` statement is to deal with the release of external resources (such as files or network connections) whether or not the attempted action has been successful.