# list.py
# Simple experiment with a list.
# We need to be able to:  declare, initialize, use.
# For more info, see section 5.1 of the Python Tutorial
#   in the ActivePython 2.6 Documentation.

list = []
for i in range(15, 25):
    list.append(i % 17)
print "Here is the list initially"
print list
# At this point, note the list has 10 elements.
# [15, 16, 0, 1, 2, 3, 4, 5, 6, 7]

# -------------------------------------------------------
# Let's find the sum of the numbers in the list.
# Note the slick way we can iterate thru the list
#   using the word "in"
sum = 0
for value in list:
    sum += value
print "The sum is " + str(sum)

# Just to illustrate, you can go thru the list the
# old-fashioned way using indices.
sum = 0
for i in range(0, 10):
    sum += list[i]
print "The sum is " + str(sum)


# Let's find the max and min.
max = list[0]
min = list[0]
for value in list:
    if value > max:
        max = value
    if value < min:
        min = value
print "The max is " + str(max)
print "The min is " + str(min)


# ---------------------------------------------------------------------
# Lists have a built-in sort() function, which doesn't return anything.
# Note that if you want to print the list concatenated onto a string,
#   you need to use str() just like we did with numbers.
list.sort()
print "Here is the new list:  " + str(list)


# ---------------------------------------------------------------------
# We can search using count() and index().
target = input("Which value would you like to search for?")
instances = list.count(target)
print str(target) + " appears " + str(instances) + " times in the list."

# Note that if the number is not in the list, count will return zero,
#   but index() will bomb.  So, let's protect ourselves.
if instances > 0:
    firstLocation = list.index(target)
    print "The first instance is at position " + str(firstLocation)


# ---------------------------------------------------------------------
# Beware of this list pitfall (aliasing error):
list2 = list
list2[0] = 99
print list
print list2
# In both lists, the first element is 99.
# What we probably intended was the following:
list[0] = 0                   # Restore original list[0] value :)
list2 = []
for value in list:
    list2.append(value)
list2[0] = 99
print list
print list2

# Note that this aliasing error does not happen for simple variable:
x = 4
y = x
x = 7
print x, y
# We see that by changing x, y is not affected.