Operators

Operators form expressions

An expression combines values, names, calls, and operators to compute a value. An operator’s operands are the values or expressions it acts on. For familiar numeric work, +, -, *, /, //, %, and ** express addition, subtraction, multiplication, true division, floor division, remainder, and exponentiation. In Python, / returns a float for numeric operands, while // discards the fractional part for the usual positive-integer examples. Thus 17 / 5 is 3.4, 17 // 5 is 3, and 17 % 5 is 2. The relationship 17 == 5 * (17 // 5) + (17 % 5) is a useful check for this example. This lesson uses arithmetic to illustrate operators; numeric types, representation, and conversion belong in the Numbers and Type Conversion lessons.

Comparison operators ask how two values relate: ==, !=, <, <=, >, and >=. A comparison evaluates to True or False. Python also permits chains such as 0 < score <= 100; the language reference specifies that comparisons chain from left to right. Chaining is not the same as comparing a Boolean to a number: it is a compact way to express a range test. Equality == asks whether values compare equal. Identity is is a different operator with a different purpose and should not be substituted for equality in ordinary value comparisons.

Logical operators and short, readable conditions

The logical operators are not, and, and or. At the precedence level relevant to ordinary Boolean expressions, not binds more tightly than and, and and binds more tightly than or. So not ready or paid and approved groups as (not ready) or (paid and approved), not as not (ready or paid) and approved. Parentheses can state the desired grouping even when a reader knows the table.

A comparison produces a Boolean result, while logical operators are typically used to combine conditions. For example, (age >= 18) and (has_ticket) describes two requirements. Keep the conditions visible instead of relying on a reader to reconstruct a dense expression. Truth testing and the fact that and and or can return an operand rather than a newly created Boolean are useful details, but they belong to the Booleans lesson rather than this introductory operator lesson. The practical habit here is to make a condition’s grouping unambiguous before using it in a later conditional.

Precedence, associativity, and assignment updates

Precedence is the priority used to group operators when parentheses do not decide the grouping. Multiplication, matrix multiplication, division, floor division, and remainder have higher precedence than addition and subtraction. Consequently, 2 + 3 * 4 evaluates as 2 + (3 * 4), producing 14; (2 + 3) * 4 produces 20. Parentheses are evaluated as a grouped expression and are the clearest way to document an exception to the normal order.

When operators share a precedence level, associativity supplies a grouping direction. Most Python operators group left to right, but exponentiation is a notable exception: ** groups right to left. Therefore 2 ** 3 ** 2 means 2 ** (3 ** 2), which is 512; (2 ** 3) ** 2 is 64. Treat that exception as a reason to parenthesize an exponent expression whose intent matters.

Assignment statements bind or rebind names. Augmented assignment combines an operation with assignment: after total = 7, total += 4 updates the name so that total is 11. Similar forms include -=, *=, /=, //=, %=, and **=. Augmented assignment is concise, but it does not erase the need to understand the operation on the right kind of value. It can also be clearer than repeating a long name on both sides of a simple update. Names and binding have their own lesson; here, the central point is that an augmented operator expresses an update using the corresponding operation.