#Mutable vs immutable.

x = 5
y= x
y = 10
print x

x = [5]
y=x
y.append(5)
print x

#calling functions.
def cube(x):
    return x**3

#Call cube to figure out the value of 5 cubed.
return *****

#Knowing the difference between print and return.
def foo(bar):
    return x

foo(10)
print foo(22)


#call with ints, call with list elements.
def mutable(x):
    x+=1
    return x

#designing boolean conditions
#traffic lights: red: stop, green = go
# yellow depends, if less than 15 metres out speed up,
# else stop.
#have colour variable: 'red' | 'green' | 'yellow'
#and dist variable.


#calculate years to retirement, given the age is less than 65 and return it.
age = raw_input()
return   **********


#lists.
def make_even(x):
    '''Take the given list of ints, and change it so that every element is even, by
    adding one to the odd numbers.'''
    
#loops with accumulators.
#Go through a list and sum the number of odd elements.
#Or go through a list, and create a dictionary where the values of
#the list elements are keys, and the indices of the elements are values.

#dictionaries.




#while loops.
#Find the index of the 4th even element in a list.
#Must use a while loop.