Using Python 3.6.4:

10.31 Implement function search() that takes as input the name of a file and the pathname of a folder and searches for the file in the folder and any folder contained in it, directly or indirectly. The function should return the pathname of the file, if found; otherwise, None should be returned. The below example illustrates the execution of search('file.txt', 'test') from the parent folder of folder 'test' shown in Figure 10.8.

>>> search('fileE.txt', 'test') test/folder2/fileE.txt