Show sequence iteration anti-pattern

Author: macdems

…er sequences Item numbering in a loop.md …emarks about iteration over sequences.md04 More on Variables/5 Two remarks about iteration over sequences Item numbering in a loop.md renamed to 04 More on Variables/5 Three remarks about iteration over sequences.md 04 More on Variables/5 Two remarks about iteration over sequences Item numbering in a loop.md renamed to 04 More on Variables/5 Three remarks about iteration over sequences.md

@@ -4,7 +4,30 @@ grand_parent: Programming for Modelling and Data Analysis
 nav_order:  5
 ---
 
-# Two remarks about iteration over sequences
+# Three remarks about iteration over sequences
+
+## Correctly iterating over sequences
+
+When iterating over a sequence, you may be tempted to use something like:
+
+<div style="text-decoration: line-through;" onmouseover="this.style.textDecoration='none'" onmouseout="this.style.textDecoration='line-through'" markdown="1">
+
+```python
+for i in range(len(sequence)):
+    element = sequence[i]
+    operate on element
+```
+
+</div>
+
+This is particularly common for people who have some experience with different programming languages, like C++. **In Python this is wrong!** Instead, you should simply iterate over sequence elements disregarding their indices:
+
+```python
+for element in sequence:
+    operate on element
+```
+
+This is much more elegant and works also with sequences that are not indexed with numbers, like dictionaries or sets.
 
 ## Item numbering in a loop
 
@@ -37,7 +60,7 @@ for element1, element2, element3 in zip(sequence1, sequence2, sequence3):
     loop block
 ```
 
-For exaple:
+For example:
 
 ```python
 first_names = ["Harry", "Frodo", "James"]

index.md

@@ -41,7 +41,7 @@ has_toc: false
 * [Lists](04%20More%20on%20Variables/2%20Lists)
 * [Dictionaries](04%20More%20on%20Variables/3%20Dictionaries)
 * [Sets](04%20More%20on%20Variables/4%20Sets)
-* [Two remarks about iteration over sequences Item numbering in a loop](04%20More%20on%20Variables/5%20Two%20remarks%20about%20iteration%20over%20sequences%20Item%20numbering%20in%20a%20loop)
+* [Three remarks about iteration over sequences](04%20More%20on%20Variables/5%20Three%20remarks%20about%20iteration%20over%20sequences)
 * [Complex numbers](04%20More%20on%20Variables/6%20Complex%20numbers)
 * [String operations](04%20More%20on%20Variables/7%20String%20operations)
 * [Variables and variable types](04%20More%20on%20Variables/8%20Variables%20and%20variable%20types)