Operators

Arithmetic: + - * / %

print(7 + 2)       # 9
print(7 / 2)       # 3.5
print(7 % 3)       # 1
print(2 * 3)       # 6

+ is overloaded:

print(1 + 2)              # 3          (numbers add)
print("foo" + "bar")      # foobar     (strings concatenate)
print("n=" + 5)           # n=5        (if either side is a string, the other is stringified)
print([1, 2] + [3, 4])    # [1, 2, 3, 4]   (lists concatenate)

* also repeats strings and lists:

print("ab" * 3)           # ababab
print([0] * 4)            # [0, 0, 0, 0]

Dividing or taking modulo by zero is a runtime error.

Comparison: == != < > <= >=

print(3 < 5)              # true
print("abc" < "abd")      # true   (lexicographic; both operands must be strings)
print([1, 2] == [1, 2])   # true   (lists/dicts compare by value, deeply)
print(1 == "1")           # false  (different types are never equal)

< > <= >= require both operands to be numbers, or both to be strings.

Logical: and / &&, or / ||, not / !

print(true and false)     # false
print(true or false)      # true
print(not true)           # false
print(a && b || c)        # && and || are aliases for and / or

and / or short-circuit and return one of their operands (not a coerced bool):

let name = user_name or "anonymous"

Assignment: =, and compound += -= *= /=

let n = 10
n += 5      # 15
n -= 2      # 13
n *= 2      # 26
n /= 2      # 13

Compound assignment works on variables and is desugared to x = x <op> y. It is not supported on properties or index targets - write those out in full: obj.count = obj.count + 1, a[i] = a[i] + 1.