how to go back a directory in python code example

Example 1: how to open csv file in python

import csv

with open('example.csv') as csvfile:
    readCSV = csv.reader(csvfile, delimiter=',')

Example 2: how to open a text file in python

f = open("demofile2.txt", "a")
f.write("Now the file has more content!")
f.close()

Example 3: python reference to back folder

os.chdir("../nodes")