dad_list.py

"""
A series of examples of list operations for Dad!

EXAMPLE 1
Start with a list of three lists: [[1,2,3], [4,5,6], [7,8,9]]
End with new lists for each position in the old list.
"""

# a list of lists, each three items long.
old_list = [
	[1, 2, 3],
	[4, 5, 6],
	[7, 8, 9],
	]
	
# list comprehensions to selectively add items from old_list	
first_items = [x[0] for x in old_list]
second_items = [x[1] for x in old_list]
third_items = [x[2] for x in old_list]

# check it works...
print(
	first_items,
	second_items,
	third_items,
	)
	
# you can filter the comprehension using a conditional statement
some_first_items = [x[0] for x in old_list if x[0] > 1]

# check it works... should be [4, 7]
print(some_first_items)

"""
EXAMPLE 2
Start with three lists: [x,x,x], [y,y,y], [z,z,z].
End with [x,y,z], [x,y,z], [x,y,z]
"""
list1 = [1, 1, 1]
list2 = [2, 2, 2]
list3 = [3, 3, 3]

# use zip() to create a zip iterable that we can iterate over: each iteration will be a tuple of the next values in each of the source lists
zip_object = zip(list1, list2, list3)
for i in zip_object:
	print(i) # or do something more useful...
	
# you can shorten the above to:
for i in zip(list1, list2, list3):
	print(i)