Assignment & Shorthand Operators

You know =. Now meet its five shortcuts — small today, but they're in *every* loop and counter you'll ever write, so let's make them automatic.

The pattern

Every shorthand does the operation AND stores the result back:

code

score = 10

score += 5     # same as: score = score + 5
print(score)   # 15

score -= 3     # score = score - 3
print(score)   # 12

score *= 2     # score = score * 2
print(score)   # 24

score /= 4     # score = score / 4
print(score)   # 6.0  ← note: /= produces a float!

score //= 2    # score = score // 2
print(score)   # 3.0

score **= 2    # score = score ** 2
print(score)   # 9.0

The full family: +=, -=, *=, /=, //=, %=, **=. Read x += 1 as *"x becomes x plus 1."*

Where you'll see += constantly: accumulators

code

total = 0
total += 250      # bought a course
total += 499      # bought another
total -= 100      # used a coupon
print(total)      # 649

And building strings:

code

receipt = ""
receipt += "1x Notebook\n"
receipt += "2x Pens\n"
print(receipt)

Accumulation — numbers climbing, strings growing — is the += family's whole personality. The quiz score, the cart total, the download progress: all +=.

The one gotcha: /= makes floats

code

count = 10
count /= 2
print(count)      # 5.0 — float, not 5!

/ always produces a float, so /= does too. If you need an int, use //= or wrap with int().

Walrus operator — the exotic cousin (meet it briefly)

Python 3.8 added := — the "walrus operator" — which assigns *inside* an expression:

code

# Instead of:
#   age = int(input("Age: "))
#   if age >= 18: ...

if (age := int(input("Age: "))) >= 18:
    print(f"Adult: {age}")

It assigns AND returns the value in one go. It's genuinely useful in specific loops — but it's also easy to overuse. For this course: know it exists, don't force it. Plain assignment is clearer 95% of the time.

Common Errors & Fixes

`NameError` on `x += 1` — += needs x to already exist. Initialize first: x = 0, then x += 1.

Surprised by `5.0` after `/=` — / floats everything; use //= for whole-number division.

`SyntaxError` on `x =+ 1` — typo, reversed characters. Python reads it as x = (+1) — assigns positive 1, no error, wrong logic. The shorthand is +=.

✅ Checkpoint

Rewrite count = count + 1 with shorthand. *(count += 1)*

What does this print? x = 2; x **= 3; print(x) *(8)*

After s = "ab"; s += "cd", what is s? *(abcd — += works on strings too)*

What's the walrus operator's symbol, and should you use it today? *(:= — know it, don't force it)*

Next: membership and identity — in, not in, is — the operators that check *what's inside what*.