10.20. Pure Functions

A pure function does not produce side effects. It communicates with the calling program only through parameters (which it does not modify) and a return value. Here is the doubleStuff function from the previous section written as a pure function. To use the pure function version of double_stuff to modify things, you would assign the return value back to things.

def doubleStuff(a_list): """ Return a new list in which contains doubles of the elements in a_list. """ new_list = [] for value in a_list: new_elem = 2 * value new_list.append(new_elem) return new_list things = [2, 5, 9] print(things) things = doubleStuff(things) print(things)

Once again, codelens helps us to see the actual references and objects as they are passed and returned.

Activity: CodeLens 10.20.2 (ch09_mod3)

Before you keep reading...

Runestone Academy can only continue if we get support from individuals like you. As a student you are well aware of the high cost of textbooks. Our mission is to provide great books to you for free, but we ask that you consider a $10 donation, more if you can or less if $10 is a burden.

Support Runestone Academy Today

Before you keep reading...

Making great stuff takes time and $$. If you appreciate the book you are reading now and want to keep quality materials free for other students please consider a donation to Runestone Academy. We ask that you consider a $10 donation, but if you can give more thats great, if $10 is too much for your budget we would be happy with whatever you can afford as a show of support.

Support Runestone Academy Today

You have attempted 1 of 3 activities on this page