Python has three different types of built-in numbers: integers (
int), floating-point (
float), and complex (
fractions.Fraction) and Decimals (
decimal.Decimal) are also available via import from the standard library.
# Ints are whole numbers. >>> 1234 1234 >>> type(1234) <class 'int'> >>> -12 -12
Numbers containing a decimal point (with or without fractional parts) are identified as
>>> 3.45 3.45 >>> type(3.45) <class 'float'>
Python fully supports arithmetic between these different number types, and will convert narrower numbers to match their less narrow counterparts when used with the binary arithmetic operators (
All numbers (except complex) support all arithmetic operations, evaluated according to operator precedence.
Support for mathematical functions (beyond
-) for complex numbers can be found in the cmath module.
Addition and subtraction operators behave as they do in normal math.
If one or more of the operands is a
float, the remaining
ints will be converted to
floats as well:
>>> 5 - 3 2 # The int is widened to a float here, and a float is returned. >>> 3 + 4.0 7.0
As with addition and subtraction, multiplication will convert narrower numbers to match their less narrow counterparts:
>>> 3 * 2 6 >>> 3 * 2.0 6.0
Division always returns a
float, even if the result is a whole number:
>>> 6/5 1.2 >>> 6/2 3.0
int result is needed, you can use floor division to truncate the result.
Floor division is performed using the
>>> 6//5 1 >>> 6//2 3
The modulo operator (
%) returns the remainder of the division of the two operands:
# The result of % is zero here, because dividing 8 by 2 leaves no remainder >>> 8 % 2 0 # The result of % is 2 here, because 3 only goes into 5 once, with 2 left over >>> 5 % 3 2
Another way to look at 5 % 3:
>>> whole_part = int(5/3) 1 >>> decimal_part = 5/3 - whole_part 0.6666666666666667 >>> whole_remainder = decimal_part * 3 2.0
Exponentiation is performed using the
>>> 2 ** 3 8 >>> 4 ** 0.5 2
Numbers can be converted from
int using the built-in functions
>>> int(3.45) 3 >>> float(3) 3.0
Python provides a built-in function
round(number, <decimal_places>) to round off a floating point number to a given number of decimal places.
If no number of decimal places is specified, the number is rounded off to the nearest integer and will return an
>>> round(3.1415926535, 2) 3.14 >>> round(3.1415926535) 3
Python allows you to use parentheses to group expressions. This is useful when you want to override the default order of operations.
>>> 2 + 3 * 4 14 >>> (2 + 3) * 4 20
Python follows the PEMDAS rule for operator precedence.
This means calculations within
() have the highest priority, followed by
>>> 2 + 3 - 4 * 4 -11 >>> (2 + 3 - 4) * 4 4 # In the following example, the `**` operator has the highest priority, then `*`, then `+` # Meaning we first do 4 ** 4, then 3 * 256, then 2 + 768 >>> 2 + 3 * 4 ** 4 770
Integers in Python have arbitrary precision -- the number of digits is limited only by the available memory of the host system.
Floating point numbers are usually implemented using a
double in C (15 decimal places of precision), but will vary in representation based on the host system.
Complex numbers have a
real and an
imaginary part, both of which are represented by floating point numbers.