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The procedure for doing that is as follows:
The earlier module titled Itse1359-1060-Syntax in this book presented and explained the two Pythonprograms shown in Listing 1 and Listing 2 . I will illustrate the use of the code visualizer with this pair of sample programs.
| Listing 1. A sample program with proper indentation. |
|---|
A = 3
B = 4if B>A:
print(A) # begin groupprint(B)
print(A + B) # end groupA = 6 # not part of above group
print(A) |
| Listing 2. Another sample program with proper indentation. |
|---|
A = 4
B = 3if B>A:
print(A) # begin groupprint(B)
print(A + B) # end groupA = 6 # not part of above group
print(A) |
When you first open the online text editor , a portion of the screen will look like Figure 1 .
Figure 1. The online text editor.
The blank portion at the top of Figure 1 is the text editor portion of the screen.
There are three drop-down boxes at the bottom of Figure 1 that allow you to selectdifferent options. The different options in these boxes control the manner in which the output information is presented as youstep through the program. In some cases, you might want to step through the same program more than once with different sets of options selected.
Figure 2 shows the result of pasting the code from Listing 1 into the text editor and pressing the button in Figure 1 labeled Visualize Execution .
Figure 2. Beginning the visualization process.
As indicated by the key in the bottom left corner of Figure 2 , two arrows will appear next to the code as you step through the code. A redarrow shows the instruction that will be executed the next time you press the Forward button. (Pressing the Back button moves the red arrowback one step.) The green arrow shows the instruction that was most recently executed. (The green arrow isn't visible in Figure 2 because it is underneath the red arrow at the beginning.)
Figure 3 shows the result of pressing the Forward button three times.
Figure 3. Output following three presses of the Forward button.
We see from the green arrow on the left that the relational test in the if statement was the most recently executed instruction.
We see on the right that the variables named A and B contain references (pointers) to objects of type int containing values of 3 and 4 respectively.
Because B is greater than A , the relational test in the if statement (pointed to by the green arrow) returned true when that statement was executed. This means that the threestatements in the indented block following the if statement will be executed. The red arrow points to the first statement in the indented blockmeaning that it will be executed the next time the user presses the Forward button.
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