From ed59cf3a435f2264754a41e2e82c8ac51a74d2fa Mon Sep 17 00:00:00 2001
From: j <jrspence@gmail.com>
Date: Wed, 29 Mar 2023 17:29:52 +0200
Subject: [PATCH] Update page 'Home'

---
 Home.md | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 59 insertions(+), 2 deletions(-)

diff --git a/Home.md b/Home.md
index 428532b..e5fe37d 100644
--- a/Home.md
+++ b/Home.md
@@ -42,7 +42,7 @@ Question: Python doesn't have the concept of multi-line comments like other C-li
  */
 ```
 
-Sometimes, you want to "turn off" a large block of code this way for testing.  How would you do that in Python?
+Sometimes, you want to "turn off" a large block of code this way for testing.  How would you do that in Python? [2]
 
 ### 2.1.4
 
@@ -90,4 +90,61 @@ Question: do you know why Python uses "j" for complex numbers instead of "i" lik
 
 You don't have to know what these operators all do... actually I don't even recognize some of them, but you should know what a `unary operator` and `binary operator` are, and the difference between them.  You can ignore the section about delimiters, that's probably included for people working on the Python interpreter itself.
 
-[1] You will probably never have to write BNF grammars, but you should be able to read them because it is by far the fastest way to learn a new language.  
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+[1] You will probably never have to write BNF grammars, but you should be able to read them because it is by far the fastest way to learn a new language.  
+
+[2] One way that I don't recommend is using triple quotes, because this still returns a string that can be cast unintentionally to a value.  I asked GPT-4 for an example and it came up with what I thought was a pretty good one:
+
+Here's an example demonstrating an unintended side effect of using triple quotes for commenting that can change the program logic:
+
+Consider the following code, where we have a function that counts the number of even numbers in a given list and has a print statement to display intermediate results:
+
+```python
+def count_evens(numbers):
+    count = 0
+    for num in numbers:
+        if num % 2 == 0:
+            count += 1
+            print(f"{num} is even.")
+    return count
+
+my_list = [1, 2, 3, 4, 5, 6]
+print(f"Number of even numbers: {count_evens(my_list)}")
+```
+
+Now, let's say we want to comment out the print statement using triple quotes:
+
+```python
+def count_evens(numbers):
+    count = 0
+    for num in numbers:
+        if num % 2 == 0:
+            count += 1
+            """
+            print(f"{num} is even.")
+            """
+    return count
+
+my_list = [1, 2, 3, 4, 5, 6]
+print(f"Number of even numbers: {count_evens(my_list)}")
+```
+
+This code seems fine at first glance, but it introduces an unintended side effect. The triple quotes are being used inside an `if` block, which means that the multi-line string created between the triple quotes is now part of the block's content. 
+
+The multi-line string is treated as an expression with a value, and since it's not `None`, it's considered a "truthy" value in a boolean context. This means that the presence of the multi-line string is affecting the control flow, and the `if` block is no longer only dependent on the `num % 2 == 0` condition. The logic of the program is unintentionally changed.
+
+To avoid this issue, you should use the hash symbol (`#`) to comment out code:
+
+```python
+def count_evens(numbers):
+    count = 0
+    for num in numbers:
+        if num % 2 == 0:
+            count += 1
+            # print(f"{num} is even.")
+    return count
+
+my_list = [1, 2, 3, 4, 5, 6]
+print(f"Number of even numbers: {count_evens(my_list)}")
+```
+
+By using the hash symbol to comment out the print statement, the program logic remains unchanged, and the control flow is not affected.
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