Changes between Version 26 and Version 27 of ControlSystems/SoftwareTeam/IntroToPython

Timestamp:

Sep 4, 2017, 5:49:45 PM (8 years ago)

Author:

cdelgigante

Comment:

--

ControlSystems/SoftwareTeam/IntroToPython

@@ -52 +52 @@
 In lesson 1, we had you create a program, "Hello World".  Now, "Hello World" is not too exciting if you want to program robots, but its an important first step.  We showed you how to run a function (or verb) `print`, which does something (show on the screen the value of its argument `a`, where `a` is assigned the value "Hello World".
 
-If you want to do more, we need to introduce control structures.  Take the program below.
+==IF-THEN-ELSE==
+If you want to do more, we need to introduce control structures.  Take the program below, it uses an IF-THEN-ELSE control structure to ask the program to make a decision, and run code based on that decision.
 
 {{{
@@ -108 +109 @@
 (Also note the text that starts with a # sign.  The pound sign and everything after it on that line is called a ''comment'', and its a way to put some notes in the code that the program doesn't run.  The team wants you to put comments in your code a lot--it makes the code easier to read and understand)
  
-Here's a couple other control structures that you should know
+Here's a couple other control structures that you should know:
 
-For Loop:  This one repeats over a variable.  It's good for counting try running this one:;
+==FOR Loop==
+The FOR loop control structure runs code repeatly repeats over a variable.  Try running this one:
+{{{
+fruits = ['banana', 'apple', 'mango']
+for fruit in fruits:       
+   print("Current fruit :", fruit)
+print("That's alotta fruit!")
+}}}
 
-For (Potato
+It should output:
 
-While:  The more charming cousin of the for loop, this one repeats
+{{{
+Current fruit : banana                                                                                                                                                                                                                                 
+Current fruit : apple                                                                                                                                                                                                                                  
+Current fruit : mango 
+}}}
+
+This example loops over an ''array'' (a fancy word for a list) of fruits, and prints each value out, each line starting with the text "Current fruit:".  To understand this, pretend that the FOR loop has a big arrow in pointing to the first value in the fruits ''array''.  The first time it runs, this arrow,{{{fruit}}} is pointing to the first value in the ''array'', {{{banana}}}, which it then sets to be the value of the index variable ''fruit''.  After it prints the message, the for loop senses through arcane magic that there are other values in fruits, so it just moves the pointer to the second value and repeats.  After the third fruit, the loop knows there's nothing left so FOR loop exits and prints "That's alotta fruit!" 
+
+Note that the "Current fruit..." print statement is indented.   Just like in a IF-THEN-ELSE control structure, you can run a block of of multiple lines of code in a for loop, just indent all the lines.
+
+FOR loops are handy if you want to avoid repeating yourself in code, and do the same thing over and over again.  The less code you write, the less chance you can make a mistake.  Not to mention its easier to read.
+
+==While Loop==
+
+A While loop, is the more charming cousin of the FOR loop, this one repeats as long as its condition is ''True''.  If the condition is false when it gets to the While loop, the While loop wont run at all.  
 
 ----