Lecture of 20th October at 9:15

(* What is the type of a range, and a list of a range? *)
>>> type(range(10))
>>> type(list(range(10)))

(* Some examples of range syntax *)
>>> range(5,10)
>>> list(range(5,10))
>>> list(range(5,10,2))

(* How do we print a range in reverse? *)
>>> list(range(10,0))
>>> list(range(10,0,-1))

(* Looping over a list using a for loop *)
>>> a = ['Mary','had','a','little','lamb']
>>> for i in range(len(a)):
>>> 	print(i, a[i])

(* An infinite loop that does not crash as it consumes no memory. Will not compile, however*)
>>> while True: pass

(* Implementing a dictionary (Similar to a hash map in java) *)
>>> superman_todo = { 1:"Get out bed", 2:"Save world", 3:"Have breakfast"}
>>> s = superman_todo
>>> s[1]

(* What values do these functions return? *)
>>> s[4]
>>> s.get(4)

(* What does the following function print out? Why? *)
>>> if s.get(4):
...   print("Hello")
... else:
...   print("Goodbye")

(* Creating an essentially empty dictionary *)
>>> t = { 1:None }
>>> t.get(1)
>>> t.get(2)

(* What does this function print out now? *)
>>> if t.get(1):
...   print("Hello")
... else:
...   print("Goodbye")

(* This is a fibonacci procedure. It is called a procedure, as it returns the value None. (There is no return) *)
>>> def fib(n):
...   a,b=0,1
...   while b < n:
...     print()
...     a,b=b,a+b

(* What is the type of this procedure? *)
>>> fib

(* The function help tells us more about the function we're using*)
>>> def obscurefunction(n):
...    """Multiplies n by 2"""
...    return 2*n

>>>  help(obscurefunction)


(* What will this function return? *)
>>> def bla(l):
...    l = []
...

>>> l = ["not","empty"]
>>> bla(l)
>>> l 

(* This function, however, does edit the contents of l. How? *)
>>> def exclamate(l):
...    l.append("!")
...

>>> exclamate(l)
>>> l

(* What is the output of exclamatebla? *)
>>> def exclamatebla(l)
...    l.append("!")
...    l = []

>>> l = ["not","empty"]
>>> exclamatebla(l)
>>> l

(* What if we use clear() instead? *)
>>> def exclamatebla(l)
...    l.append("!")
...    l.clear()

>>> l = ["not","empty"]
>>> exclamatebla(l)
>>> l

(* Changing the index works by reference, changing the list itself works by value. What should this function return? *)
>>> def crazyfun(l)
...    l[0]="Joanne"
...    l = []

>>>  l = ["Jamie"]
>>> crazyfun(l)
>>> l

(* This function asks for the global value of l, rather than the local one. *)
>>> def clear_l(l):
...    global l
...    l = []

(* What does this output then? *)
>>> l = ['not','empty']
>>> clear_l(l)
>>> print(l)