Programming Patterns

• Tranform Pattern
• Filter Pattern
• Nested Loops

Tranform Pattern

• Change the value each item in a sequence (list, tuple, range, string) using an expression
• Input: sequence
• Processing: expression/function
• Output: sequence of transformed values

Tranform Example

• take a list and raise to the second power

mylist = [1,2,3,4,5,6,7,8]
newlist = []
for n in mylist:
    newlist.append(n ** 2)
print(newlist)

Filter Pattern

• Select items that meet specitied conditions
• Input: Sequence
• Processing: if statement
• Output: sequence subset

Filter Pattern Example

mylist = [1,2,3,4,5,6,7,8]
newlist = []
for n in mylist:
    if n% 2 == 0:
        newlist.append(n)
print(newlist)

# Output
[2,4,6,8]

set into an item in mylist:

• first iteration n is set to 1

Nested Loops

• A way for combining every item in multiple sequences

• more of a construct than a direct input processing output pattern that the transform and filter a combination og every item in every sequence

• Loop inside a loop
  • an inner loop is completed for each iteration of an outer loop
• outer loop
  • inner loop
    • innerer loop body
  • outer loop body
• for each iteration of an outer loopall possible combinations or words in two sequences

adjectives = ['frozen','cooked','roasted','boiled']
nouns = ['fish','veggies','chicken']

for adj in adjectives:
    # outer loop
    for noun in nouns:
        # inner loop
        print(f"{adj} {noun}", end="\t")
    print()

# Output
frozen fish frozen veggies frozen chicken
cooked fish cooked veggies cooked chicken
roasted fish roasted veggies roasted chicken