How to check one file exists or not code example

Example 1: check if a file exists

>>> import os
>>> os.path.isfile("d:\\Package1\\package1\\fibo.py")
True
>>> os.path.isfile("d:/Package1/package1/fibo.py")
True
>>> os.path.isfile("d:\\nonexisting.txt")

Example 2: if file exist

file_exists ( string $filename ) : bool