Numbers in Python
Let's try some more python commands.
1. Numbers
The interpreter acts as a simple calculator: you can type an expression at it and it will write the value. Expression syntax is straightforward: the operators
+
, -
, *
and /
work just like in most other languages (for example, Pascal or C); parentheses (()
) can be used for grouping. For example:
The integer numbers (e.g.
2
, 4
, 20
) have type int
, the ones with a fractional part (e.g. 5.0
, 1.6
) have typefloat
. We will see more about numeric types later in the tutorial.
Division (
/
) always returns a float. To do floor division and get an integer result (discarding any fractional result) you can use the //
operator; to calculate the remainder you can use %
:
With Python, it is possible to use the
**
operator to calculate powers [1]:
The equal sign (
=
) is used to assign a value to a variable. Afterwards, no result is displayed before the next interactive prompt:
If a variable is not “defined” (assigned a value), trying to use it will give you an error:
There is full support for floating point; operators with mixed type operands convert the integer operand to floating point:
In interactive mode, the last printed expression is assigned to the variable
_
. This means that when you are using Python as a desk calculator, it is somewhat easier to continue calculations, for example:
This variable should be treated as read-only by the user. Don’t explicitly assign a value to it — you would create an independent local variable with the same name masking the built-in variable with its magic behavior.
In addition to
int
and float
, Python supports other types of numbers, such as Decimal
and Fraction
. Python also has built-in support for complex numbers, and uses the j
or J
suffix to indicate the imaginary part (e.g. 3+5j
).
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