05 Apr 2026

Operators and Expressions

Arithmetic, comparison, logical operators, precedence, and expression building in Python.

msc semester-i computational-techniques operators python

Most formulas in physics become expressions in a program. An expression combines values, variables, and operators to produce a new value. For example, the formula for kinetic energy becomes a Python expression involving multiplication and powers.

The important point is that the computer follows definite rules of precedence. If the intended mathematical grouping is not obvious, parentheses should be used.

Arithmetic operators

a = 10
b = 3

print(a + b)
print(a - b)
print(a * b)
print(a / b)
print(a**b)

The operator ** is used for powers.

In physics programs, powers occur frequently in expressions such as $v^2$, $r^2$, and $x^3$. In Python these are written as v**2, r**2, and x**3.

Comparison operators

Comparison operators produce True or False.

x = 5

print(x > 0)
print(x == 5)
print(x != 3)

Use == for comparison and = for assignment.

Logical operators

Logical operators combine conditions.

temperature = 310
pressure = 1.2

safe = temperature < 350 and pressure < 2.0
print(safe)

Common logical operators are and, or, and not.

Precedence

Python follows mathematical order of operations.

value = 2 + 3 * 4
print(value)

Multiplication is done before addition. Use parentheses when the intended order should be made explicit.

value = (2 + 3) * 4

Physics example

m = 1.5
v = 4.0
h = 2.0
g = 9.8

energy = 0.5 * m * v**2 + m * g * h
print(energy)

This expression computes kinetic plus gravitational potential energy.

Displacement expression

For a particle moving with uniform acceleration, the displacement is

\[s=ut+\frac12at^2.\]

In Python this may be written as

u = 2.0
a = 3.0
t = 4.0

s = u * t + 0.5 * a * t**2
print(s)

The value printed is 32.0.

Logical test

A result can be tested by combining comparison and logical operators.

energy = -2.0
normalised = True

acceptable = energy < 0 and normalised
print(acceptable)

This gives True only when both conditions are satisfied.

Practice questions

1. Distinguish between assignment = and comparison ==.
2. Write a Python expression for $s=ut+\frac12at^2$.
3. What is the output of 2 + 3 * 4? Explain the order of operations.
4. Give one example each of an arithmetic, comparison, and logical operator.
5. Write a logical expression that is true only when energy is negative and the state is normalized.