Chapter 3. Functions
In the context of programming, a function is a named sequence of statements that performs a computation. When you define a function, you specify the name and the sequence of statements. Later, you can “call” the function by name. We have already seen one example of a function call:
>>> type(32) <type 'int'>
The name of the function is
type. The expression in parentheses is called
the argument of the function. The
result, for this function, is the type of the argument.
It is common to say that a function “takes” an argument and “returns” a result. The result is called the return value.
Type Conversion Functions
Python provides built-in functions that convert values
from one type to another. The
function takes any value and converts it to an integer, if it can, or
>>> int('32') 32 >>> int('Hello') ValueError: invalid literal for int(): Hello
int can convert floating-point
values to integers, but it doesn’t round off; it chops off the fraction
>>> int(3.99999) 3 >>> int(-2.3) -2
float converts integers and
strings to floating-point numbers:
>>> float(32) 32.0 >>> float('3.14159') 3.14159
str converts its
argument to a string:
>>> str(32) '32' >>> str(3.14159) '3.14159'
Python has a math module that provides most of the familiar mathematical functions. A module is a file that contains a collection of related functions.
Before we can use the module, we have to import it:
>>> import math
This statement creates a ...