Debugging short exercise - Revision history

Admin at 03:03, 4 February 2011

2011-02-04T03:03:10Z

Admin at 03:01, 4 February 2011

2011-02-04T03:01:46Z

Admin at 02:58, 4 February 2011

2011-02-04T02:58:07Z

Admin at 04:14, 3 February 2011

2011-02-03T04:14:34Z

Admin at 03:39, 3 February 2011

2011-02-03T03:39:16Z

Admin: Created page with "'''Objective''': Practice debugging techniques This program is supposed to break once the ball has been caught, but it doesn't work. Your job is to work out why, and then fix it..."

2011-02-03T03:30:53Z

Created page with "'''Objective''': Practice debugging techniques This program is supposed to break once the ball has been caught, but it doesn't work. Your job is to work out why, and then fix it..."

New page

'''Objective''': Practice debugging techniques

This program is supposed to break once the ball has been caught, but it doesn't work.
Your job is to work out why, and then fix it.

# Download [[media:Catch-debug-exercise.py]] and open it in Dr. Python
# Add print statements to trace program execution <br /><syntaxhighlight lang="python"> print "Trace: At start" </syntaxhighlight>
##Start of the program
##Once the game window has been created
##Inside of the main game update loop
##Inside of the ''if'' statement that checks if the ball has been caught
##End of program
# Run the program and stop it ''as soon as the buggy behavior has occurred''.
# Analyse the console output (the debug 'trace'). <br /> What would you expect to see if the program was running properly?
#Is the problem that the distance isn't being properly calculated? <br /> Add another print statement that prints it.
# Once you've worked out what the real problem is, fix it.
# Submit your code to school web locker

@@ Line 11: / Line 11: @@
 ##Inside of the ''if'' statement that checks if the ball has been caught
 ##End of program
-# Add another print statement before the 'if' statement (so that it runs on every iteration),  like this: <syntaxhighlight lang="python"> print "Distance/ball to mitt: ", round(distance(ball_x, ball_y, mitt_x, mitt_y)) </syntaxhighlight> <br/> '
+# Print the distance before the 'if' statement (so that it runs on every iteration): <syntaxhighlight lang="python"> print "Distance/ball to mitt: ", round(distance(ball_x, ball_y, mitt_x, mitt_y)) </syntaxhighlight> <br/> '
 # Run the program and stop it ''as soon as you notice the buggy behavior''.
 # Analyse the console output (the debug 'trace'). <br /> '''Is the execution sequence what we would expect?''' (e.g. is it getting to the right place in the code at the right time?) <br />   '''Are the values what we would expect?'''

@@ Line 11: / Line 11: @@
 ##Inside of the ''if'' statement that checks if the ball has been caught
 ##End of program
 # Run the program and stop it ''as soon as you notice the buggy behavior''.
-# Analyse the console output (the debug 'trace'). <br /> ''Is the  execution sequence what we would expect ? (e.g. is it getting to the right place in the code at the right time?)  ''
+# Analyse the console output (the debug 'trace'). <br /> '''Is the execution sequence what we would expect?''' (e.g. is it getting to the right place in the code at the right time?) <br />   '''Are the values what we would expect?'''
 # Once you've worked out what the problem is, fix it.
 # ''Name your file "MY_NAME_DEBUG_EX.txt"'' and then submit your code to school web lockers.

@@ Line 11: / Line 11: @@
 ##Inside of the ''if'' statement that checks if the ball has been caught
 ##End of program
-# Run the program and stop it ''as soon as the buggy behavior has occurred''.
+# Run the program and stop it ''as soon as you notice the buggy behavior''.
-# Analyse the console output (the debug 'trace'). <br /> What would you expect to see if the program was running properly?
+# Analyse the console output (the debug 'trace'). <br /> ''Is the  execution sequence what we would expect ? (e.g. is it getting to the right place in the code at the right time?)  ''
-#Is the problem that the distance isn't being properly calculated?  <br /> Add another print statement before the 'if' statement,  like this: <syntaxhighlight lang="python"> print "Distance: ", round(distance(ball_x, ball_y, mitt_x, mitt_y)) </syntaxhighlight>
+# Add another print statement before the 'if' statement (so that it runs on every iteration),  like this: <syntaxhighlight lang="python"> print "Distance/ball to mitt: ", round(distance(ball_x, ball_y, mitt_x, mitt_y)) </syntaxhighlight> <br/>
-# Once you've worked out what the real problem is, fix it.
+# Once you've worked out what the problem is, fix it.
-# Submit your code to school web locker
+# ''Name your file "MY_NAME_DEBUG_EX.txt"'' and then submit your code to school web lockers.
 <syntaxhighlight lang="python">
@@ Line 21: / Line 22: @@
 def distance(x1, y1, x2, y2):
-     return ((x2 - x1)**2 + (y2 - y1)**2)**0.5
+     return ((x2 + x1)**2 + (y2 + y1)**2)**0.5
 begin_graphics(800, 600, title="Catch", background=color.YELLOW)
@@ Line 29: / Line 30: @@
 ball_y = 300
 ball = Circle((ball_x, ball_y), 10, filled=True)
 dx = 4
 dy = random_between(-4, 4)
@@ Line 45: / Line 47: @@
          dx *= -1
      # check on the mitt
      if key_pressed('k') and mitt_y <= 580:
@@ Line 54: / Line 52: @@
      elif key_pressed('j') and mitt_y >= 20:
          mitt_y -= 5
      if key_pressed('escape'):
@@ Line 60: / Line 62: @@
      move_to(mitt, (mitt_x, mitt_y))
-     if distance(ball_x, ball_y, mitt_x, mitt_y) <= -30:  # ball is caught
+     if distance(ball_x, ball_y, mitt_x, mitt_y) <= 30:  # ball is caught
          remove_from_screen(ball)
          break

@@ Line 13: / Line 13: @@
 # Run the program and stop it ''as soon as the buggy behavior has occurred''.
 # Analyse the console output (the debug 'trace'). <br /> What would you expect to see if the program was running properly?
-#Is the problem that the distance isn't being properly calculated?  <br /> Add another print statement that prints it,  like this: <syntaxhighlight lang="python"> print "Distance: "+ distance(ball_x, ball_y, mitt_x, mitt_y) </syntaxhighlight>
+#Is the problem that the distance isn't being properly calculated?  <br /> Add another print statement before the 'if' statement,  like this: <syntaxhighlight lang="python"> print "Distance: ", round(distance(ball_x, ball_y, mitt_x, mitt_y)) </syntaxhighlight>
 # Once you've worked out what the real problem is, fix it.
 # Submit your code to school web locker
@@ Line 34: / Line 34: @@
 mitt_x = 740
 mitt_y = 300
-mitt = Circle((mitt_x, mitt_y), 60)
+mitt = Circle((mitt_x, mitt_y), 30)
 while True:
@@ Line 60: / Line 60: @@
      move_to(mitt, (mitt_x, mitt_y))
-     if distance(ball_x, ball_y, mitt_x, mitt_y) <= -60:  # ball is caught
+     if distance(ball_x, ball_y, mitt_x, mitt_y) <= -30:  # ball is caught
          remove_from_screen(ball)
          break

@@ Line 4: / Line 4: @@
 Your job is to work out why, and then fix it.
-# Download [[media:Catch-debug-exercise.py]] and open it in Dr. Python
+# Copy the program at the bottom of this page, and open it in Dr. Python
-# Add print statements to trace program execution <br /><syntaxhighlight lang="python"> print "Trace: At start" </syntaxhighlight>
+# Add print statements to trace program execution, like this: <syntaxhighlight lang="python"> print "Trace: At start" </syntaxhighlight> Add at least five statements:
 ##Start of the program
 ##Once the game window has been created
@@ Line 13: / Line 13: @@
 # Run the program and stop it ''as soon as the buggy behavior has occurred''.
 # Analyse the console output (the debug 'trace'). <br /> What would you expect to see if the program was running properly?
-#Is the problem that the distance isn't being properly calculated?  <br /> Add another print statement that prints it.
+#Is the problem that the distance isn't being properly calculated?  <br /> Add another print statement that prints it,  like this: <syntaxhighlight lang="python"> print "Distance: "+ distance(ball_x, ball_y, mitt_x, mitt_y) </syntaxhighlight>
 # Once you've worked out what the real problem is, fix it.
 # Submit your code to school web locker