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Lecture 4, Tue 08/14

if/else, for, input

Code from class

https://github.com/ucsb-cs8-m18/code-from-class/tree/master/08-14

Python round function: https://docs.python.org/3.7/library/functions.html#round

Logging into CSIL from MacOS or Linux

ssh -X pconrad@csil-21.cs.ucsb.edu

The first time you’ll get a message such as:

ECDSA key fingerprint is SHA256:ANJ7ced3JXpxKnu8OhnS3f8Z0rE9aIKA+eHHgVlEzVc.
Are you sure you want to continue connecting (yes/no)? yes

Just say yes.

Machines are 01-48

CTRL/D can be used to exit.

For Windows, the program is MobaXTerm

To use it, look for “New Session” in upper left,

Then “ssh” upper left.

Then enter csil-15.cs.ucsb.edu (or whatever number) where it asks for host.

Then, you’ll be prompted for username and password.

If you get this message when running idle3

or any other program that needs graphics…

_tkinter.TclError: no display name and no $DISPLAY environment variable

On Windows: Use MobaXTerm instead of a program such as PuTTY.

On Mac: You need to install XQuartz … go to XQuartz.org, download, follow instructions, and try again.

Also: on Mac or Linux, maybe you forgot the -X part. If that still doesn’t work, see me and I’ll follow the instructions on this page with you: https://stackoverflow.com/questions/39622173/cant-run-ssh-x-on-macos-sierra.

Installing pytest

Mac:

One of the following will work:

pip3 install pytest
python3 -m pip install pytest

Windows:

open command prompt, and type:

python -m pip install pytest

If that doesn’t work, you’ll need to add python to your PATH using this: https://projects.raspberrypi.org/en/projects/using-pip-on-windows/5

When you use SSH, you connect to another computer. Changes you make to the files on that computer don’t appear on your own computer.

The line “import blah” asks Python to look for a file named blah.py. So don’t name your Python program “turtle.py”, because then “import turtle” won’t find the correct module.

iClicker Questions

  1. What does the following code print out?

    x = 5 if x < 7: print(x) x = x + 7 else: print(x) x = x - 7 if x < 7: print(x)

    (a) 5 12 5

    (b) 5 12

    (c) 5

    (d) None of the above

  2. How many things are wrong with the following code? It’s supposed to print out “0\n1\n2\n3\n4\n5\n6”, where each \n is a new line.

    for i in range(10): if i < 7: print(i)

    (a) 0 (b) 1 (c) 2 (d) ≥ 3

In-Class Questions

  1. Write a program that takes a price input from the user, adds 7.75% tax to it, and then outputs the new price.

  2. Write a function called calculate_grade that takes in a percentage, and prints a string: That string should be “pass” if the percentage is ≥ 60, and “fail” if it’s smaller than 60.

  3. Change the function to return the string instead of printing it.