Fun with Python : Interactive Python - "Stopwatch: The Game"

Mini-project description - "Stopwatch: The Game"

Let's combining text drawing in the canvas with timers to build a simple digital stopwatch that keeps track of the time in tenths of a second. The stopwatch should contain "Start", "Stop" and "Reset" buttons.

Mini-project development process

1. Construct a timer with an associated interval of 0.1 seconds whose event handler increments a global integer. (Remember that create_timer takes the interval specified in milliseconds.) This integer will keep track of the time in tenths of seconds. Test your timer by printing this global integer to the console. Use the CodeSkulptor reset button in the blue menu bar to terminate your program and stop the timer and its print statements. Important: Do not use floating point numbers to keep track of tenths of a second! While it's certainly possible to get it working, the imprecision of floating point can make your life miserable. Use an integer instead, i.e., 12 represent 1.2 seconds.

2. Write the event handler function for the canvas that draws the current time (simply as an integer, you should not worry about formatting it yet) in the middle of the canvas. Remember that you will need to convert the current time into a string using str before drawing it.

3. Add "Start" and "Stop" buttons whose event handlers start and stop the timer. Next, add a "Reset" button that stops the timer and reset the current time to zero. The stopwatch should be stopped when the frame opens.

4. Next, write a helper function format(t) that returns a string of the form A:BC.D where A, C and D are digits in the range 0-9 and B is in the range 0-5. Test this function independent of your project. Note that the string returned by your helper function format should always correctly include leading zeros. For example

• format(0) = 0:00.0

• format(11) = 0:01.1

• format(321) = 0:32.1

• format(613) = 1:01.3

Hint: Use integer division and remainder (modular arithmetic) to extract various digits for the formatted time from the global integer timer.

5. Insert a call to the format function into your draw handler to complete the stopwatch. (Note that the stopwatch need only work correctly up to 10 minutes, beyond that its behavior is your choice.)

6. Finally, to turn your stopwatch into a test of reflexes, add to two numerical counters that keep track of the number of times that you have stopped the watch and how many times you manage to stop the watch on a whole second (1.0, 2.0, 3.0, etc.). These counters should be drawn in the upper right-hand part of the stopwatch canvas in the form "x/y" where x is the number of successful stops and y is number of total stops. My best effort at this simple game is around a 25% success rate.

7. Add code to ensure that hitting the "Stop" button when the timer is already stopped does not change your score. We suggest that you add a global Boolean variable that is True when the stopwatch is running and False when the stopwatch is stopped. You can then use this value to determine whether to update the score when the "Stop" button is pressed.

8. Modify "Reset" so as to set these numbers back to zero when clicked.

Steps 1-3 and 5-7 above are relatively straightforward. However, step 4 requires some adept use of integer division and modular arithmetic. So, we again emphasize that you build and debug the helper function format(t) separately

Answer: Access my code here 

Fun with Python : Interactive Python - “Guess The Number” Game

“Guess the number” game
One of the simplest two-player games is “Guess the number”. The first player thinks of a secret number in some known range while the second player attempts to guess the number. After each guess, the first player answers either “Higher”, “Lower” or “Correct!” depending on whether the secret number is higher, lower or equal to the guess. In this project, you will build a simple interactive program in Python where the computer will take the role of the first player while you play as the second player.
You will interact with your program using an input field and several buttons. For this project, we will ignore the canvas and print the computer's responses in the console. Building an initial version of your project that prints information in the console is a development strategy that you should use in later projects as well. Focusing on getting the logic of the program correct before trying to make it display the information in some “nice” way on the canvas usually saves lots of time since debugging logic errors in graphical output can be tricky.
Mini-project development process
A basic template for this mini-project here (http://www.codeskulptor.org/#examples-guess_the_number_template.py). Suggested development strategy for the basic version of “Guess the number” is:

1. Decide on a set of global variables that contain the state of the game. For example, one obvious choice is the secret number that has been generated by the program. You will need other global variables, especially to accommodate later extensions to the basic game.
2. Figure out how to generate a random secret number in a given range, low to high. When discussing ranges, we will follow the standard Python convention of including the low end of the range and excluding the high end of the range, which can be expressed mathematically as [low, high). So, [0, 3) means all of the numbers starting at 0 up to, but not including 3. In other words 0, 1, and 2. We suggest using the range [0, 100) in your first implementation. Hint: look at the functions in the random module to figure out how to easily select such a random number. We suggest testing this in a separate CodeSkulptor tab before adding code to your project.
3. Figure out how to create an input text box using the simplegui module. You will use this input to get the guess from the user. For all variants of the game, this input field should always be active (in other words, a game should always be in progress). Again, test in a separate CodeSkulptor tab before adding code to your project.
4. Write the event handler input_guess(guess) that takes the input guess, compares it to the secret number and prints out the appropriate response. Remember that guess is a string so you will need to convert it into a number before testing it against the secret number. Hint: We have showed you how to convert strings to numbers in the lectures.
5. Test your code by playing multiple games of “Guess the number” with a fixed range. At this point, you will need to re-run your program between each game (using the CodeSkulptor “Run” button).
6. Fill in your new_game() function so the generation of the secret number is now done inside this function. That is, calling new_game() should compute a random secret number and assign it to a global variable. You can now call the function new_game() in the body of your code right before you start your frame.

From this minimal working version of “Guess the number”, the rest of this project consists of adding extra functionality to your project. There are two improvements that you will need to make to get full credit:
1. Using function(s) in the simplegui module, add buttons to restart the game so that you don't need to repeatedly click “Run” in CodeSkulptor to play multiple games. You should add two buttons: “Range: 0 - 100” and “Range: 0 - 1000” that allow the player to choose different ranges for the secret number. Using either of these buttons should restart the game and print out an appropriate message. They should work at any time during the game. In our implementation, the event handler for each button set the desired range for the secret number (as a global variable) and then call new_game to reset the secret number in the desired range.
As you play “Guess the number”, you might notice that a good strategy is to maintain an interval that consists of the highest guess that is “Lower” than the secret number and the lowest guess that is “Higher” than the secret number. A good choice for the next guess is the number that is the average of these two numbers. The answer for this new guess then allows you to figure a new interval that contains the secret number and that is half as large. For example, if the secret number is in the range [0, 100), it is a good idea to guess 50. If the answer is "Higher", the secret number must be in the range [51, 100). It is then a good idea to guess 75 and so on. This technique of successively narrowing the range corresponds to a well-known computer algorithm known as binary search.

2. Your final addition to “Guess the number” will be to restrict the player to a limited number of guesses. After each guess, your program should include in its output the number of remaining guesses. Once the player has used up those guesses, they lose, the game prints out an appropriate message, and a new game immediately starts.
Since the strategy above for playing “Guess the number” approximately halves the range of possible secret numbers after each guess, any secret number in the range [low, high) can always be found in at most n guesses where n is the smallest integer such that 2 ** n >= high - low + 1. For the range [0, 100), n is seven. For the range [0, 1000), n is ten. In our implementation, the function new_game() set the number of allowed guess to seven when the range is [0, 100) or to ten when the range is [0, 1000). For more of a challenge, you may compute n from low and high using the functions math.log and math.ceil in the math module.
When your program starts, the game should immediately begin in range [0, 100). When the game ends (because the player either wins or runs out of guesses), a new game with the same range as the last one should immediately begin by calling new_game(). Whenever the player
clicks one of the range buttons, the current game should stop and a new game with the selected range should begin.

Grading — 11 pts total
Here is a break down of the scoring:
1 pt — The game starts immediately when the “Run” button in CodeSkulptor is pressed.
1 pt — A game is always in progress. Finishing one game immediately starts another in the same range.
1 pt — The game reads guess from the input field and correctly prints it out.
3 pts — The game correctly plays “Guess the number” with the range [0, 100) and prints understandable output messages to the console. Play three complete games: 1 pt for each correct game.
2 pts — The game includes two buttons that allow the user to select the range [0, 100) or the range [0, 1000) for the secret number. These buttons correctly change the range and print an appropriate message. (1 pt per button.)
2 pts — The game restricts the player to a finite number of guesses and correctly terminates the game when these guesses are exhausted. Award 1 pt if the number of remaining guesses is printed, but the game does not terminate correctly.
1 pt — The game varies the number of allowed guesses based on the range of the secret number — seven guesses for range [0, 100), ten guesses for range [0, 1000).
To help aid you in gauging what a full credit project might look like, the video lecture on the “Guess the number” project includes a demonstration of our implementation of this project. You do not need to validate that the input number is in the correct range. (For this game, that responsibility should fall on the player.)

Answer :  Access my code here

Control of Mobile Robots - - Week 1 Exercise

You got a score of 4.00 out of 5.00.

Question 1

One way of getting a general feeling for what a differential equation is up to is to look at the sign and magnitude of the derivative at different points for different values of x. Use this idea for the dynamics

x˙(t)=−x(t)3.

Which one of the plots below (where t is on the ``x-axis" and x(t) is on the ``y-axis") was generated by this system? Note that x(0)=10.

Your Answer
	Correct	1.00

Question ExplanationThe first thing to check is what the axes and the initial condition for each plot is; in our case, these are plots of x(t) that start at x0=10. Thus, the correct plot will (at least initially) have a negative rate of change (x˙(0)=−1000 to be exact). Working through using process of elimination we find the correct plot.

Question 2

One way of modeling epidemics is to describe how the fraction of infected individuals evolves over time. Let I be that fraction, with the model being

I˙=βI(1−I)−ρI.

Here, the constants β and ρ are the infection and recovery rates, respectively. What are the possible equilibrium points to this system (values for I when the fraction of infected individuals is not changing)?

Your Answer		Score	Explanation
When I=0 or I=(β−ρ)/β	Correct	1.00
Only when I=(β−ρ)/β
When I=0 or I=(1−β)/ρ
Only when I=(1−β)/ρ
Only when I=0
Total		1.00 / 1.00

Question ExplanationWe need to see what happens when I(t) does not change, i.e., when I˙=0. So, solve βI(1−I)−ρI=0. This is a 2nd-order polynomial equation, which means it has two solutions (although the two solutions may be the same).

Question 3

If someone gives you a possible solution to a differential equation, one of the checks needed to see if this is indeed a solution is by taking the required number of derivatives and seeing if the proposed solution does in fact satisfy the differential equation. Let

x¨(t)=−ω2x(t).

Which of the following options is not a possible solution to this equation?

Your Answer		Score	Explanation
x(t)=0
x(t)=cos(ωt)
x(t)=e−ωt	Correct	1.00
x(t)=sin(ωt)
x(t)=ωsin(ωt)−cos(ωt)
Total		1.00 / 1.00

Question ExplanationPlugging in each function and differentiating twice we get a second derivative that is not the same as the function in the question for one of the choices.

Question 4

We saw that the model of a cruise-controller could be given by

x˙=cmu−γx,

where u is the input, x is the speed of the car, and c,m,γ are constant parameters. If there was no wind resistance in the cruise-control model (γ=0), what would the steady-state values be for the velocity x when using a pure D-regulator, i.e., when u=ke˙=k(r˙−x˙)=−kx˙ (since r is constant)?

Your Answer		Score	Explanation
x(∞)=0
x(∞)=r
x(∞)>r
Impossible to say
x(∞) less than r	Inorrect	0.00
Total		0.00 / 1.00

Question ExplanationPlugging in our choice of controller u=−kx˙ and γ=0 as well we get: x˙=−kcmx˙, which is no longer a differential equation. Think in terms of discrete time: xk+1=xk+dt``x˙′′ but what is x˙ now? And how can we determine x now?

Question 5

Let a discrete-time system be given by

xk+1=max{0,5−xk}.

If this system starts at x0=10, what happens to the state of the system?

Your Answer		Score	Explanation
It keeps switching between 0 and -5
It keeps growing from 10 up to ∞
It jumps down to x1=0 and increases up by one until x5=5 and then jumps back to 0 again (and the process repeats)
It keeps switching between 0 and 5	Correct	1.00
It jumps down to x1=0 and remains at 0 for ever
Total		1.00 / 1.00

Question ExplanationStart by plugging in x0=10. Find x1. Keep plugging in, using this discrete update rule, until you see the pattern start to repeat. Be careful -- it's easy to make simple mistakes in your addition!