some_list = []
some_list.append(5)
some_list.append(6)
some_list.append(7)

print some_list
for item in some_list:
    print item

# Write Python code to calculate the average of the numbers in some_list; it should work for any set of numbers in some_list.

average = 0.
for num in some_list:
    average += num
    
average = average / len(some_list)
print average

# for example, combining lists [] and dicts {} can be useful:
letters_list = ['a', 'b', 'c', 'd', 'e']

letters_dict = {}

for i in range(len(letters_list)):
    single_letter = letters_list[i]
    letters_dict[single_letter] = i

some_list = ["duck", "goose", "mouse", "mouse", "mouse", "duck"]

counts = {}
counts["duck"] = 0

for item in some_list:
    if item == "duck":
        counts["duck"] += 1

## Write Python code to generically count the number of times *each* item in some_list is there.
## The output should be in dictionary format, e.g. 'print counts["duck"]' should show '2'.

counts = {}

# first, set counts[item] to 0 for all possible items
for item in some_list:
    counts[item] = 0
    
# next, count!
for item in some_list:
    counts[item] += 1
    
print counts

def add_two_numbers(a, b):
    c = a + b
    return c

add_two_numbers(5, 10)

# make the below code work by defining a new function, 'average'

def average(x):
    total = 0.
    for item in x:
        total += item
    return total / len(x)

some_list = []
some_list.append(5)
some_list.append(6)
some_list.append(7)
print average(some_list)

def count_items(x):
    d = {}
    for item in x:
        d[item] = d.get(item, 0) + 1
    return d

some_list = ["duck", "goose", "mouse", "mouse", "mouse", "duck"]

counts_dict = count_items(some_list)
print "duck shows up", counts_dict["duck"], "times"

# !gist class3-lists-dicts-functions.ipynb