Oct 12th, 2020
Q: Hello, the lecture slides are still not on the website, it gives an error saying " object not found"
A1: Working on this! Thanks!
Q: What is the best way to copy/duplicate an image?
A1: You can make another image from the same filename.
Q: Do we not have an assignment #4 this week?
A1: It comes out on Wednesday!
Q: when is this data from
A1: Not positive, but I believe it is from a few years ago
Q: If you submit an assignment late on the due date, does that count as an entire late day?
A1: Yes. Anything that comes in after the time that the assignment is due is considered late.
Q: When we make another image from the same filename, how exactly do we copy it onto the blank canvas we make? I am having some trouble
A1: You can copy an image pixel by pixel into a new blank image.
Q: how do we copy an image to another blank image/slate?
A1: You can copy the image pixel by pixel (in a loop). For example, you might want to check out the mirror example from class last week.
Q: I missed the beginning, are diagnostic scores going to available after class? Where do I check this?
A1: There will be an announcement posted on the course website at the end of class.
Q: What outside resources/tools do you reccommend we use to practice coding?
A1: You could check out parlante.org. It has practice problems in Python and was developed by Nick Parlante (lecturer at Stanford)
Q: why did pixel.red have to add (R*proportion + G*proportion + B*proportion) and not just the R*proportion?
A1: That's just the way the sepia filter is defined to get the right effect. You can find out more here: https://www.techrepublic.com/blog/how-do-i/how-do-i-convert-images-to-grayscale-and-sepia-tone-using-c/
Q: does it matter whether you nest your loops by x or y first?
A1: It is convention to loop over y in the outer list. But you can also loop over with x as the outer list.
Q: So as opposed to matrices in math, pixels are (col, row) since it’s (x,y)?
A1: In lists of lists, we think of the rows as the first index and columns as the second index.
Q: For the warhol image problem, is it ok to import random library to use?
A1: Yes
Q: when will we be able to make insta
A1: You're getting closer!
Q: can you store an image in a global variable?
A1: You can, but using global variables is generally bad style.
Q: what's the best way to iterate through a list while simultaneously removing elements in the list?
A1: This is actually a dangerous thing to do. You generally want to create a new list that only contains the elements of the original list that you care about.
Q: Is there a way to change the border color?
A1: Yes. Use outline= parameter.
Q: can we use a canvas for the warhol assignment?
A1: You should not need to.
Q: The fill and outline parameters are imported using one of the libraries right?
A1: They are part of the create_rectangle (and other functions) that are part of the library tkinter.
Q: what’s the purpose of the ‘hello rect’?
A1: Just to show you a simple example of graphics.
Q: is 600, 600 the endpoint or the distance from the specified origin?
A1: Endpoint
Q: Is there a way to draw these shapes rotated on an angle?
A1: You'd need to figure out the coordinates for the rotated object manually (but there are libraries to help with that).
Q: How come the line does not go through the blue squre or red oval
A1: The square and the circle are on top of the line.
Q: how frequently are the mouse positions updating? or can we specify a framerate?
A1: Its set by how often the operating system notifies python of mouse movement.
Q: How is Chris getting negative y-coordinates when mousing over the graphic? like occasionally y = -1 will pop up
A1: Didn't see that, but it might be an artifact of the window bounds.
Q: Does the console showing the x and y values of where the mouse is happen automatically? Or does that need to be programmed?
A1: That needs to be programmed.
Q: sorry, I missed what the anchor means?
A1: It is which point on the object you want to specify the x and y location. So if you want to specify the NW corner, or the SW corner, or just the West point.
Q: Do peple in industry typically use python for graphics or another language?
A1: Depends on the application. But heavy graphics (e.g., movie making) uses other languages (sometime specialized for the application).
Q: When we take the next diagnostic, can we use these SimpleImage/tkinter reference sheets or must we remember all the functions eventually?
A1: You can use these reference sheets!
Q: Is there a way to see the potential arguments of a function while your defining it?
A1: Some development environments may provide that information, but the documentation is always the best source to go to.
A2: You can checkout this handout for a list of helpful graphics functions. It shows the parameters. http://web.stanford.edu/class/cs106a/handouts/graphics-reference.html
Q: is the border for all shapes automatically black? or is that hiding in the code somewhere? thank you!
A1: The border color defaults to black.
Q: For coding graphics is it again standard to declare numbers as global constants or can we just use numbers in the body of code?
A1: Declare them as constants!
Q: How do we to write a Python library tkinter or simpleimage?
A1: Come chat about this at office hours!
Q: Can you shut off the chat?
A1: You can close the chat panel by clicking on the "Chat" icon in zoom. Sometimes the instructors use the chat to get feedback from the class.
Q: why aren’t the global variables n_rows and n_cols being used in the example?
A1: They were just added.
Q: why do we need to minus 1 for the constant SIZE? for furture questions, is that always the case we should do? thx for answering!
A1: Depends on the application. It was done here so the last square wouldn't go off the end of the canvas (since we start counting from location 0,0)
Q: can y = row * size be moved to be below for row and above for col?
A1: Yes!
Q: I’m trying to run Canvas in Python, but it appears that there is a package missing. Do I need to download Canvas, tkinter, or graphics, or is there something else I’m missing? Thanks!
A1: you need some import statements. import tkinter and from graphics import Canvas
Q: how max long a variable or method name can be?
A1: Longer than you'd actually want to use. It depends on the interpretter you're using. But it's as long as you need for practical purposes.
Q: is it bad if we set each patch individually in assignment 3 for the warhol program?
A1: This might be a good question for Ed! We can help give you a more complete answer.
Q: are we allowed to use the "not in" operator to compare lists?
A1: Yes
Q: what was the type command for creating our own function
A1: Higlight code, right click, refactor, extract method
Q: Is canvas an immutable or mutable type?
A1: Mutable
Q: Can you please define binding again?
A1: Check out this handout: http://web.stanford.edu/class/cs106a/handouts/mutation.html
Q: How does this apply to mutable vs immutable variables? Is this "url" type thing what happens with integers and floats and stuff?
A1: Ints and floats are immutable. Lists are mutable. Check out the handout on binding and mutation.
Q: for the warhol assignment how do you pass images into a list and then transfer it to an x,y coord on the canvas? would you use a for loop and append each image to a list? ty!
A1: This might be better answered on Ed! Post on there so that we can provde a more in depth answer.
Q: Can we use list.clear() to clear lists after an iteration?
A1: It might be better style to instead create a new list at the beginning of each iteration.
Q: where can we see our scores for the diagnostic?
A1: There will be a link on the class website soon where you can see your grade.
Q: Where can we see our diagnostic grade?
A1: There will be a link on the class website soon where you can see your grade.
Q: where do we see the diagnostic results?
A1: On an announcement on the course website
Q: If we want to know where we’re at in the class, do we talk to our section leader?
A1: Or you can talk to Juliette