reorg and add code for second edition

07_trees/python/01_filesystem_dfs.py

@@ -0,0 +1,18 @@
+from os import listdir
+from os.path import isfile, join
+
+
+def printnames(dir):
+    # loop through every file and folder in the current folder
+    for file in sorted(listdir(dir)):
+        fullpath = join(dir, file)
+        if isfile(fullpath):
+            # if it is a file, print out the name
+            print(file)
+        else:
+            # if it is a folder, call this function recursively on it
+            # to look for files and folders
+            printnames(fullpath)
+
+
+printnames("pics")