Introduction to Programming using Python

ion The possibility to define such new function executing tasks specified by yourself, is an abstraction feature, provided by all high level programming languages. Important It is also important to notice that functions have to be defined before they are called. You can not use something that is not defined. Here is the syntax of such a new definition in Python: >>> from string import * >>> def gc(seq): ... return float(count(seq, ’G’) + count(seq, ’C’)) / len(seq) Let’s have a closer look at this definition. Figure 8.1 illustrates the structure of a function definition.