Numeric Types: int and float

15 min · Beginner

Python has two primary numeric types for everyday programming: int for whole numbers and float for decimal values.

Arbitrary-precision integers

Integer (int) is the type for whole numbers such as 7, 0 or -250. A Python int has no fixed size, so it never overflows.

In Python 3, integers have arbitrary precision. Unlike Java's 32-bit int or 64-bit long, Python integers never overflow.

Python

big_number = 10 ** 30print(big_number)

Example 1 · An integer that never overflows

Python

print(2 ** 100)

Output

1267650600228229401496703205376

What this code does

2 ** 100 means 2 raised to the power 100.
The result is far larger than 64 bits, and Python prints it exactly.

Python automatically allocates as many bytes of memory as needed to store the exact integer value.

Readability with underscores

When writing large numbers, place underscores between digits to make the value easy to read. Python ignores the underscores.

Python

annual_revenue = 1_500_000print(annual_revenue)

The console prints 1500000. Use underscores for currency, serial codes, or financial figures.

Floating-point numbers and precision

Float is the type for numbers with a decimal point, such as 68.5. Floats are stored in binary, so some decimals are only close approximations.

A float represents a real number with a decimal point. Python floats follow the IEEE 754 double-precision standard.

Python

weight = 68.5ratio = 1e-3print(weight)print(ratio)

Example 2 · A float is an approximation

Python

total = 0.1 + 0.2print(total)print(round(total, 2))

Output

0.30000000000000004
0.3

What this code does

0.1 and 0.2 cannot be stored exactly in binary.
Their sum prints with a tiny error at the end.
round(total, 2) gives the clean value 0.3.

1e-3 represents scientific notation for 1 * 10⁻³, which evaluates to 0.001.

Rounding with round()

round() is a built-in function that returns a number rounded to a given count of decimal places. Without the count it returns a whole number.

Use the built-in round(number, digits) function to round a floating-point number to a specific number of decimal places.

Python

price = 19.8567print(round(price, 2))

Example 3 · Interest on a savings balance

Python

1account_balance = 2_500_0002interest_rate = 0.07253interest_earned = account_balance * interest_rate4
5print(account_balance)6print(interest_earned)7print(round(interest_earned, 2))

Output

2500000
181250.0
181250.0

What this code does

account_balance uses underscores for readability.
interest_earned calculates 2500000 * 0.0725 = 181250.0.
round() formats the float to 2 decimal places.

The console displays 19.86. When digits is omitted, round() returns the nearest integer.

Next step

Check your understanding

9 quick questions

Numeric Types: int and float

15 min · Beginner

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Python has two primary numeric types for everyday programming: int for whole numbers and float for decimal values.

Arbitrary-precision integers

Integer (int) is the type for whole numbers such as 7, 0 or -250. A Python int has no fixed size, so it never overflows.

In Python 3, integers have arbitrary precision. Unlike Java's 32-bit int or 64-bit long, Python integers never overflow.

Python

big_number = 10 ** 30print(big_number)

Example 1 · An integer that never overflows

Python

print(2 ** 100)

Output

1267650600228229401496703205376

What this code does

2 ** 100 means 2 raised to the power 100.
The result is far larger than 64 bits, and Python prints it exactly.

Python automatically allocates as many bytes of memory as needed to store the exact integer value.

Readability with underscores

When writing large numbers, place underscores between digits to make the value easy to read. Python ignores the underscores.

Python

annual_revenue = 1_500_000print(annual_revenue)

The console prints 1500000. Use underscores for currency, serial codes, or financial figures.

Floating-point numbers and precision

Float is the type for numbers with a decimal point, such as 68.5. Floats are stored in binary, so some decimals are only close approximations.

A float represents a real number with a decimal point. Python floats follow the IEEE 754 double-precision standard.

Python

weight = 68.5ratio = 1e-3print(weight)print(ratio)

Example 2 · A float is an approximation

Python

total = 0.1 + 0.2print(total)print(round(total, 2))

Output

0.30000000000000004
0.3

What this code does

0.1 and 0.2 cannot be stored exactly in binary.
Their sum prints with a tiny error at the end.
round(total, 2) gives the clean value 0.3.

1e-3 represents scientific notation for 1 * 10⁻³, which evaluates to 0.001.

Rounding with round()

round() is a built-in function that returns a number rounded to a given count of decimal places. Without the count it returns a whole number.

Use the built-in round(number, digits) function to round a floating-point number to a specific number of decimal places.

Python

price = 19.8567print(round(price, 2))

Example 3 · Interest on a savings balance

Python

1account_balance = 2_500_0002interest_rate = 0.07253interest_earned = account_balance * interest_rate4
5print(account_balance)6print(interest_earned)7print(round(interest_earned, 2))

Output

2500000
181250.0
181250.0

What this code does

account_balance uses underscores for readability.
interest_earned calculates 2500000 * 0.0725 = 181250.0.
round() formats the float to 2 decimal places.

The console displays 19.86. When digits is omitted, round() returns the nearest integer.

Next step

Check your understanding

9 quick questions