Lecture Notes for CPSC 121 (Fall 2012) - Myro Functions, Lists, and For Loops, Study notes of Computer Science

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Today ...

• Myro functions
• More lists
• For loops (intro)

Reading

• Ch 4

HW

• HW 6 out
• Proj 1 out

Some basic Myro functions

• beep(d, f) ... beeps duration d with frequency f
• getName() ... name of your robot
• getInfo() ... get information about robot
• setName(s) .. set robot name to str s
• forward(a, s) ... move forward speed a, seconds s
• backward(a, s) ... move backward speed a, seconds s
• turnLeft(a, s) ... turn left speed a, seconds s
• turnRight(a, s) ... turn right speed a, seconds s There are lots more functions
• e.g., for interacting with sensors
• we’ll look at more as we go

List Functions

The len function returns the length of a list

len([10, 20, 30]) 3 empty = [] len(empty) 0 The append function adds an element to the end of a list empty.append(10) print(empty) [10] empty.append(20) print(empty) [10, 20]

The remove function removes the first matching value in a list

empty.remove(10) print(empty) [20]

The del keyword deletes an element at a given index (subscript)

del empty[0] print(empty) []

The reverse function reverses a list

the list = ["spam", "ham", "eggs"] the list.reverse() print(the list) ["eggs", "ham", "spam"]

More on indexing

my_list = [6, 7, 9] Q: What is the length of the list? Q: What function do we call to get the length ... len() list_length = len(my_list) print(list_length) 3

Q: What is the index of the first list element?

my_list = [6, 7, 9] elem = my_list[0] print(elem) 6

• list elements are indexed from 0 to length - 1

Q: What happens if we give an index outside of 0 to length - 1?

elem = my_list[3] IndexError: list index out of range elem = my_list[-1] # a special case! print(elem) 9 elem = my_list[-4] IndexError: list index out of range

The for statement

Iteration (looping) allows us to repeat blocks of code For example, instead of writing: the list = ["spam", "ham", "eggs"] print(the list[0]) print(the list[1]) print(the list[2])

We can use a for statement: for v in the list: print(v)

• Note we don’t need to know the length of the list here!