# 3.1: Function calls

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We have already seen one example of a function call:

>>> type(42)
<class '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 also called the return value.

Python provides functions that convert values from one type to another. The int function takes any value and converts it to an integer, if it can, or complains otherwise:

>>> 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 part:

>>> 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


Finally, str converts its argument to a string:

>>> str(32)
'32'
>>> str(3.14159)
'3.14159'


This page titled 3.1: Function calls is shared under a CC BY-NC 3.0 license and was authored, remixed, and/or curated by Allen B. Downey (Green Tea Press) .