Putting it all together

Putting it all together

• You now know variables, input, if, loops, lists, functions, and dictionaries.
• A real program combines these small pieces into one useful tool.
• In this lesson you build a tiny class-scores analyzer, one function at a time.

The plan

• We have a list of test scores, like [70, 90, 50, 80].
• We want three answers: the average, how many passed, and a short summary.
• We will write one small function for each job, then they work together.

Handy built-ins for lists

• Python gives you ready-made helpers that work on a list of numbers.
• len(x) counts the items, sum(x) adds them, max(x) / min(x) find the largest / smallest.
• Use them instead of writing a loop every time.

scores = [70, 90, 50, 80]
print(len(scores))   # 4
print(sum(scores))   # 290
print(max(scores))   # 90
print(min(scores))   # 50

A pattern you will reuse: count items that pass a test

• A very common job: loop a list, and count the items that pass some test.
• Start a counter at 0, and add 1 each time the if is true.
• Here we count the long words; soon you will count the passing scores.

def how_many_long_words(words, min_length):
    count = 0
    for w in words:
        if len(w) >= min_length:
            count = count + 1
    return count

print(how_many_long_words(["hi", "hello", "hey", "howdy"], 4))   # 2

Common mistakes

• Build in small pieces and test each one before adding the next.
• Read the whole task first, then plan before you code.

Now you try

• Build the analyzer in three steps: average, count_passing, then stats.
• Each function is small. Together they turn a list of scores into real answers.
• Press Check answer after each one.