# Programming Languages (F28PL) lecture transcript - 19th October at 15:15

# Transcript starts @ 23:00.

# Demonstrating iteration over other types:
x = "Hello World"
for l in x:
    print(l)
# Will print each character in "Hello World" sequentially, as strings are
# iteratable types

x[2] # will return l

# Example exam question: reverse a string using python using python indexing
# functions

def reversestring(s):
    return s[-1::-1] # s[::-1] also works

reversestring(x) # will return "dlroW olleH"

# to demonstrate the use of break
primelist = []
for n in range(2, 100):
    for x in range(2, n): # n/2 will also work
        if n % x == 0:
            break 
    else: # BEWARE! Indentation is important! This else belongs to the for loop
        primelist.append(n)
print(primelist)

pass # does nothing

superman_todo = {1:"Get out of bed", 2:"Save world", 3:"Eat breakfast"} # dictionary: key-value data structure
type(superman_todo) # <class 'dict'>

superman_todo[1] # "Get out of bed"
superman_todo[2] # "Save world"
superman_todo[3] # "Breakfast"
superman_todo[4] # Error!

# demonstrating .get() function
superman_todo.get(1) # "Get out of bed"
superman_todo.get(2) # "Save world"
superman_todo.get(3) # "Breakfast"
superman_todo.get(4) # Returns NoneType. Note difference to the previous example
print(superman_todo.get(4)) # prints 'None' to console

# procedure as an object
reversestring # returns the location in memory

5**100 is 5**100 # returns false, as there exists two 5*100's in memory

5**2 is 5**2 # returns true, as python caches numbers between -5 and 256 such
#that when you create an int in that range you actually just get back a reference to
#the existing object. https://docs.python.org/2/c-api/int.html https://docs.python.org/3/c-api/long.html