Day 07: Weekly review — values, conditions, and safe Git

Instructions

Spaced review: Days 04–05 were two to three days ago, so today you retrieve them before rereading anything. Pulling an idea back from memory, then checking it, makes it last longer than rereading notes. Nothing in this activity is new.

1. Close your notes. For each value in the first snippet, write the three columns you expect: repr, type name, and bool. Also predict the last line (len counts Unicode code points, not bytes).
2. Run the snippet and mark every row where your prediction differed.
3. Repeat with the binding snippet: predict both lines, then run it.
4. For each mismatch, write one sentence naming the rule you forgot and the day that teaches it (Day 04 for values, Day 05 for mutation and identity).

def show(value):
    print(repr(value), type(value).__name__, bool(value))
show(0.0)
show("0.0")
show("")
show("猫")
show([""])
show(None)
print(len("猫"), len("café"))

a = ["猫"]
b = a
a.append("犬")
print(b, a is b)
c = ["猫"]
d = c
c = c + ["犬"]
print(d, c is d)

Instructions

Spaced review: this revisits Day 05 (comparisons) and Day 06 (conditions) with new inputs, so you cannot rely on remembered answers.

1. Predict the five booleans printed by the comparison line, then run it.
2. Without looking at Day 06, write label(raw): strip the text; return "missing" if the result is the empty string; return "number " plus the integer value if the stripped text is decimal; otherwise return "text " plus the stripped text. Predict the six printed lines before running your version.
3. Compare your function with the reference below and run both.

print(0 == 0.0, "0" == 0, None is None, [] == [], [] is [])

def label(raw):
    text = raw.strip()
    if text == "":
        return "missing"
    if text.isdecimal():
        return "number " + str(int(text))
    return "text " + text
print(label("  猫 "))
print(label(""))
print(label("   "))
print(label("007"))
print(label("-3"))
print(label("٣"))

Optional preview for Day 08 (not assessed, scaffolded): run the loop below and only observe that its body runs once per character. You will study loops properly tomorrow.

for ch in "猫a":
    print(ch, ch == "a")

Instructions

Spaced review: inspecting a diff before committing was practiced on Days 04 and 06; today you repeat it from memory in a fresh fixture. New today (scaffolded): By default, git restore FILE restores a tracked file in the working tree from the index (staging area); it does not change the index or unstage changes. In this fixture the index equals HEAD (the latest commit), so it discards the unstaged edit by restoring that committed version. It cannot undo a commit; Day 09 covers that.

Work only in a new temporary directory, never in the curriculum repository. Before each command, write what you expect it to print (an empty output counts as a prediction). Then run the whole sequence:

cd "$(mktemp -d)"
git init -q
git config user.name "Learner"
git config user.email "[email protected]"
printf 'label: 猫\n' > notes.txt
git add notes.txt
git commit -q -m "Add notes"
printf 'label: 猫\ncount: 1\n' > notes.txt
git diff --stat
git diff --check
git add notes.txt
git commit -q -m "Add count line"
git log --format=%s
printf 'oops\n' >> notes.txt
git status --short
git restore notes.txt
git status --short
cat notes.txt

Instructions

Spaced review: this is the weekly consolidation check for Days 04–06. Do not open the reference answer or use AI until your evidence is submitted.

1. Predict, in writing, the three lines printed by this snippet, then run it:

print(repr("0"), bool("0"), "0" == 0)
x = ["a"]
y = x
x.append("é")
print(y)
x = ["a"]
y = x
x = x + ["é"]
print(y)

2. From scratch, write describe(raw): return "empty" when the stripped text is empty, "digits" when it is decimal, otherwise "text". Predict and then test it on "", " ", "42", "４２" (full-width digits), and "猫".
3. From memory, list the commands you would run in a disposable repository to inspect a change before committing it, and the command that discards an uncommitted edit to a tracked file.