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
Syntax for opening file is:
file object = open(file_name [, access_mode][, buffering])
As you have not mentioned access_mode(optional), default is 'Read'. But if file 'test.txt' does not exists in the folder where you are executing script, it will through an error as you got.
To correct it, either add access_mode as "a+" or give full file path e.g. C:\test.txt (assuming windows system)
python 2.7: Testing text file in idle