184_notes:lists

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184_notes:lists [2022/04/20 15:07] – created woodsna1184_notes:lists [2022/05/07 01:20] (current) – woodsna1
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 ====== Coding: Lists ====== ====== Coding: Lists ======
  
-We often need a way to represent a group of objects or values in code. Python makes this easy with lists. A list gives a name to a collection of any Python objects. In Glowscript, we often use lists that include spheres, arrows, rings, and other shapes. Creating a list is easy:+We often need a way to represent a group of objects or values in code. Python makes this easy with lists. A list gives a name to a collection of any Python objects. You can think of a list like an excel spreadsheet, it has many rows (each representing an object), and each row has several columns (representing the attributes of the object).  
 + 
 +In Glowscript, we often use lists that include spheres, arrows, rings, and other shapes. Creating a list is easy:
  
 <code>  <code> 
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 </code> </code>
  
-You can think of a list like a column in an excel spreadsheet, it has many fields that can each be filled with an object. You can also access each bucket in a list to update or retrieve the object within it. One way is by using list indexing. Indices in a Python list start at 0 for the first element:+You can also access each bucket in a list to update or retrieve the object within it. One way is by using list indexing. Indices in a Python list start at 0 for the first element:
  
 <code> <code>
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 </code> </code>
  
-To change the value in a bucket, simply use = to assign to it:+To change the value in a bucket, simply use "=" to assign to it:
 <code> <code>
 list_of_numbers[0] = 250               # Change the first element list_of_numbers[0] = 250               # Change the first element
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 ===== Lists and For Loops ===== ===== Lists and For Loops =====
 +==== Lecture Video ====
 +
 +{{youtube>Rvpmo95XBNA?large}} 
 We often want to move through a list and read or change each value one-by-one. The easiest way to iterate through a list in Python is using a for loop.  We often want to move through a list and read or change each value one-by-one. The easiest way to iterate through a list in Python is using a for loop. 
  
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 </code> </code>
  
-This works great for reading each element in a list. In the above code, "number" is a temporary variable. On each iteration of the for loop, number is assigned to the next element in the list "list_of_numbers" until none are left. Within the for loop, you can use the variable "number" to access the current element in the list. **The above loop does not work for changing values in the list** to change values, we need to use a different kind of loop. Usually, the best choice is to use a while loop as below:+This works great for reading each element in a list. In the above code, "number" is a temporary variable. On each iteration of the for loop, number is assigned to the next element in the list "list_of_numbers" until none are left. Within the for loop, you can use the variable "number" to access the current element in the list. **The above loop does not work for changing values in the list**. To change values, we need to use a different kind of loop. Usually, the best choice is to use a while loop as below:
  
 <code>  <code> 
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 index = 0 index = 0
  
-while index < len(list_of_numbers): +while index < len(list_of_numbers):  # Conditional 
-    list_of_numbers[index] += 1 +    list_of_numbers[index] += 5      # Increase each number by 5 
-    index += 1+    index += 1                       # Increment the counter variable
 </code> </code>
  
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  • Last modified: 2022/04/20 15:07
  • by woodsna1