I m using the command testFile = open("test.txt") to open a simple text file and received the following: Does such errors occur due to the version of python one uses? 
IOError: [Errno 2] No such file or directory: 'Test.txt
The error is independent from the version, but it is not clear 
what you want to do with your file.
If you want to read from it and you get such an error, it means that your file is not where you think it is. In any case you should write a line like testFile = open("test.txt","r").
If you want to create a new file and write in it, you will have a line like
testFile = open("test.txt","w"). Finally, if your file already exists and you want to add things on it, use testFile = open("test.txt","a") (after having moved the file at the correct place). If your file is not in the directory of the script, you will use commands to find your file and open it.
python 2.7: Testing text file in idle