8.2. Opening files¶
When we want to read or write a file (say on your hard drive), we first
must open the file. Opening the file communicates with
your operating system, which knows where the data for each file is
stored. When you open a file, you are asking the operating system to
find the file by name and make sure the file exists. In this example, we
open the file mbox.txt, which should be stored in the same
folder that you are in when you start Python. You can download this file
For learning purposes, we are using the shortened version of this file
mbox-short.txt This file can be found and downloaded from
Click on the button to show the first lines from this file.
open is successful, the operating system returns
a file handle object. The file handle object is not the actual data
contained in the file, but instead it is a “handle” that we can use to
read the data. You are given a handle if the requested file exists and
you have the proper permissions to read the file.
If the file does not exist,
open will fail with a traceback
and you will not get a file handle object.
>>> fhand = open('stuff.txt') Traceback (most recent call last): File "<stdin>", line 1, in <module> FileNotFoundError: [Errno 2] No such file or directory: 'stuff.txt'
Later we will use
except to deal more
gracefully with the situation where we attempt to open a file that does