Lab Assignment 1

Note

    1. You are allowed to form a group of two to do this lab assignment.

    2. You are strongly recommended to bring your own laptop to the lab with Anaconda1 and Pycharm2 installed. You don’t even have to attend the lab session if you know what you are required to do by reading this assignment.

    3. Python 2.x and Python 3.x are both acceptable. But you need to specify the python version in requirements.txt. For example, if your scripts are required to run in Python
2.7, the following line should appear in requirements.txt:

python_version == '2.7'

    4. For those of you using the Windows PC in SHB 924A (NOT recommended) with your CSDOMAIN account3, please login and open “Computer” on the desktop to check if an “S:” drive is there. If not, then you need to click “Map network drive”, use “S:” for the drive letter, fill in the path \\ntsvr6\userapps and click “Finish”. Then open the “S:” drive, open the Python2 folder, and click the “IDLE” shortcut to start doing the lab exercises. You will also receive a paper document and if anything has changed, please be subject to the paper.

    5. The programming assignments are graded by Python scripts on linux! Just a reminder, the subscript we provide can be used only on Linux for your own test. For those who use Windows, you may not use our test scripts so you can test your solution on your own. If your script does not pass the tests of our grading script, which support both Linux and Windows, you cannot get full grades. You are able to test the input and output format for a exercise by the corresponding testing script. For example, by running test_p1.py, you can test p1.py for exercise 1. Note that the grading script will be DIFFERENT from the provided testing script. To use our testing scripts, you should install package pexpect, and run the testing script in the same folder of the script.









1An open data science platform powered by Python. https://www.continuum.io/downloads

2

3A non-CSE student should ask the TA for a CSDOMAIN account.


1 of 5
CSCI 2040    Lab Assignment 1    Page 2


Exercise 1: The Second Smallest & Biggest Number (20

marks)

raw_input() in Python 2 (equivalent to input() in Python 34) is a function that read a string from a user’s input. The function can be used as raw_input(['prompt']). For example, after executing x = raw_input('type a number:') and reading the user typed “one”, the variable x will store the string ”one”.
Write a script and save it as p1.py that will read four numeric values from the user’s input. If the input is not a numeric value, then the user should be asked again to input a numeric value and this round does not count. After that, print the second smallest and biggest of the four inputted values, print the line Program ends. and exit. A sample run should be as follows: (Hint: use float() to convert a string to the corresponding numeric value)

Please input the first number: 4.1

Please input the second number: joke

Your input is not a number!

Please input the second number: -5

Please input the third number: 23.16

Please input the fourth number: -3.02

The second smallest value is -3.02

The second biggest value is 4.1

Program ends.

If you use IDLE, you can test your script p1.py in the Python shell with

    • execfile(’path/to/p1.py’)

Exercise 2: Right-angled Triangle Pattern of A String

(20 marks)

Using while loop or for loop to write a script p2.py that reads an integer value n and a string str from the user’s input and then produces an n-line block, repeatedly. For the n-line output, the first line contains 1 str, the second line contains 2 strs, and so on until the n-th line, which contains only n strs. Print the pattern as a right-angled triangle. The script will keep asking the user to input an integer value n and a string s and then print the corresponding n-line block. The script will print the line Program ends. and exit if the user inputs an integer -1. For this exercise, you don’t need to check whether the user’s input is an integer or not. A sample run should be as follows:

Enter an integer: 4

Enter a string:1


    • Stackoverflow: What’s the difference between raw_input() and input() in python3.x?


2 of 5
CSCI 2040    Lab Assignment 1    Page 3



1

11

111

1111

Enter an integer: 2

Enter a string:^_^

^_^

^_^^_^

Enter an integer: -1

Program ends.

Exercise 3: GPA Calculator (20 marks)

In order to improve GPA (Grade Point Average), the first thing at hand is to write a script that calculate GPA quickly. With the script, a user could input the grade, credit and major indicator(1 means major course, 0 otherwise) of a course. Immediately after reading the grade for a course, the GPA calculator print out the current GPA and major GPA. The user could keep adding the grades for more and more courses until the user inputs -1. When the user inputs -1, the script will print the line Program ends. and exit. The grade, credit and major indicator are separated by space. If the grade or credit inputted is negative, your script should print Wrong input! and continue to wait for new inputs. We assume major indicator is always 0 or 1. The GPA MUST be in the format of 2 decimal points. (Hint: Use "0:.2f".format(a) if you want to output 2 decimal points of a) A sample run should be as follows:

3.731

Current GPA: 3.70

Current major GPA: 3.70

3.320

Current GPA: 3.54

Current major GPA: 3.70

-2.5 2 0

Wrong input!

-1

Program ends.

Exercise 4: Guess My Number (20 marks)

Hint: To hide the input in Python, you could simply replace input() with getpass.getpass().




3 of 5
CSCI 2040    Lab Assignment 1    Page 4



import getpass

getpass.getpass()

After knowing that the GPA is improved, the students want to play some games to relax. They decide to play guess my number. Specifically, one of the player selects a integer in the range [−100, 100] and report it to the computer when seeing the prompt Player 1, write down your number secretly:. If the input is not in the range, then Player 1 should be asked again to input a numeric value. After that, the script prompts another player for a guess with the message Player 2, input your guess:. At each step, the script responds one of the following 4 sentences:

Your guess is too low!

Your guess is too high!

You are right after trying for n times.    Program ends.

You have tried 6 times and it is still wrong! The answer is ans and program ends. Here n is the number of times that the user has tried to guess the random integer correctly which is less than 6. And ans is the answer Player 1 inputted. A sample run should be like as follows,


Player 1, write down your number secretly:

Player 1, invalid input, write down your number secretly:

Player 2, input your guess: 0

Your guess is too low!

Player 2, input your guess: 100

Your guess is too high!

Player 2, input your guess: 12

Your guess is too high!

Player 2, input your guess: 9

You are right after trying for 4 times. Program ends.


Exercise 5: Palindrome Wonderland (20 marks)

In a secret place near the back hill of CUHK, there is a palindrome wonderland. People there uses palindrome as their language. A palindrome is a string that reads the same backward and forward. For example, the string eye and the string able was I ere I saw elba are both palindromes. The palindrome wonderland has an entrance guard, which only allows the people speaking palindrome to pass. You would implement such an entrance guard in p5.py.

The entrance guard start with the prompt Please input a palindrome: that first reads a string from the user’s input and check whether the input string is a palindrome or not and the scripts would not exit until a palindrome is inputted. The script will print Welcome to the wonderland! and the script exits if the input string is a palindrome. Otherwise, it will print No, you must input a palindrome: and keep asking the user to input another


4 of 5
CSCI 2040    Lab Assignment 1    Page 5


string if the input string is not a palindrome. For this exercise, uppercase and lowercase letters are treated as different characters. Also if there are any space character in the string, we just omit it.Hint: you can use raw_input() in Python 2 or input() in Python 3. A sample run should be like as follows,

Please input a palindrome: 210

No, you must input a palindrome: 012

No, you must input a palindrome: Nba A B n

No, you must input a palindrome: NBa a B N

Welcome to the wonderland!


Submission rules

    1. Please name the script files with the exact names specified in this assignment and test all your scripts. Any script that has any syntax error will not be marked.
    2. For each group, please pack all your script files as a single archive named as

<student-id1>_<student-id2>_lab1.zip

For example, 1155012345_1155054321_lab1.zip, i.e., just replace <student-id1> and <student-id2> with your own student IDs. If you are doing the assignment alone, just leave <student-id2> empty, e.g, 1155012345_lab1.zip.

    3. Upload the zip file to your blackboard ( https://blackboard.cuhk.edu.hk),

        ◦ Only one member of each group needs to upload the archive file.

        ◦ Subject of your file should be <student-id1>_<student-id2>_lab1 if you are in a two-person group or <student-id1>_lab1 if not.

        ◦ No later than 23:59 on Wednesday, Sept. 30

    4. Students in the same group would get the same marks. Marks will be deducted if you do not follow the submission rules. Anyone/Any group caught plagiarizing would get 0 score!



















5 of 5