@@ -0,0 +1,287 @@
+__author__ = 'Sungho Park'%0A%0Aimport os%0A%0A__directory_queue = %5B%5D%0A%0A%0Adef pushd():%0A    %22%22%22%0A    push current directory to queue%0A    %22%22%22%0A    cwd = os.getcwd()%0A%0A    __directory_queue.append(cwd)%0A%0A%0Adef popd():%0A    %22%22%22%0A    change directory to popped.%0A    %22%22%22%0A    os.chdir(__directory_queue.pop())%0A%0A

Add filesystem functions. The first function is pushd and popd.