Python Literals

What are literals in Python?

A literal is a value written directly in Python source code. The number 42, the text "Python", and the Boolean value True are all literals. A variable is a name that refers to a value; the literal is the value itself.

count = 42
language = "Python"
ready = True
missing = None

Types of Python literals

Numeric literals

Numeric literals create int, float, or complex values. Python integers can grow beyond the size commonly supported by a fixed-width integer type, subject to available memory.

Integer literals

decimal_number = 25
binary_number = 0b11001
hex_number = 0x19
print(decimal_number, binary_number, hex_number)

Floating-point and complex literals

A floating-point literal contains a decimal point or an exponent. A complex literal uses j or J for its imaginary part:

price = 19.95
large_value = 2.5e3       # 2500.0
complex_value = 2 + 3j
print(price, large_value, complex_value)

Binary floating-point values are approximations, so use decimal.Decimal when exact decimal arithmetic is required, such as for some financial calculations.

String literals

String literals represent text and can use single quotes, double quotes, or triple quotes. Choose a quoting style that keeps the text readable:

single = 'Python'
double = "Programming"
multi_line = """This text
uses more than one line."""
print(single, double)
print(multi_line)

Escape sequences

Formatted string literals

F-strings insert expressions into text using an f prefix:

name = "Asha"
score = 92
print(f"{name} scored {score}")

Boolean literals

Python has two Boolean literals: True and False. They are commonly produced by comparisons and used by if statements:

is_adult = age >= 18
if is_adult:
    print("Access allowed")

Use the exact capitalized spellings. true and false are not Python Boolean literals.

Collection literals

numbers = [10, 20, 30]
coordinates = (12.9, 77.6)
student = {"name": "Asha", "level": 1}
unique_numbers = {10, 20, 20, 30}
print(numbers, coordinates, student, unique_numbers)

An empty list is [], an empty dictionary is {}, and an empty set must be created with set() because {} means an empty dictionary.

The special literal None

None represents “no value” or “not available yet.” It is not the same as zero, an empty string, or False. Check it with identity comparison:

result = None
if result is None:
    print("No result is available")

Literals and mutability

Writing a literal creates a value, but whether that value can be changed depends on its type. Lists, sets, and dictionaries are mutable; numbers, strings, tuples, and Boolean values are immutable. Assigning a new value to a variable changes what the name refers to; it does not change an immutable value in place.

Common mistakes

• Using true, false, or NULL instead of True, False, or None.
• Using {} when an empty set was intended; use set().
• Forgetting that input from input() is a string literal until it is converted.
• Comparing with is when value equality with == is required.