Numbers

Integer numbers

Numerical values without decimal places are called integers or ints. In Python, integers are a predefined data type.

a = 42

Floating-point numbers

Numbers with decimal places are called floating-point numbers or floats.

b = 42.0
pi = 3.14159

Arithmetical Operators

The arithmetical symbols like + - * / connecting two numbers are called operators. In addition to the standard arithmetics a few other operators are available:

a = 7
b = 4
c = a - b
d = a * b
e = a / b
f = a % b      # modulo, 3
g = a ** 2     # 49
h = 7.0 // b   # floor division, 1.0

If you perform arithmetics with integer numbers, the result is also an integer. If one of the numbers is a float, the result will also be a float. When you perform a division, the result is always a floating-point number.

Rounding and binary representation

Occasionally, seemingly simple floating-point calculations will result in strange results, e.g. instead of 0.3 you might see:

>>> 0.1 + 0.2
0.30000000000000004

This is related to the underlying binary representation of floating-point numbers. The precision of floats is by default 16 digits, which is enough for most applications (be aware that it might not, if you are doing astrophysics or other high-precision calculations).

(This happens in all programming languages that use floats with limited precision, but they might round the floats automatically.)