Page 64 - Programming the Raspberry Pi Getting Started with Python

The line f.close() has been added. You should always call the close command when you are done
with a file to free up operating system resources. Leaving a file open can lead to problems.
The full program is contained in the file 06_01_hangman_file.py, and a suitable list of animal
names can be found in the file hangman_words.txt. This program does nothing to check that the file
exists before trying to read it. So, if there file isn’t there, we get an error that looks something like

this:

To make this a bit more user friendly, the file-reading code needs to be inside a try command, like
this:

Python will try to open the file, but because the file is missing it will not be able to. Therefore, the
except part of the program will apply, and the more friendly message will be displayed. Because we

cannot do anything without a list of words to guess, there is no point in continuing, so the exit
command is used to quit.
In writing the error message, we have repeated the name of the file. Sticking strictly to the Don’t
Repeat Yourself (DRY) principle, the filename should be put in a variable, as shown next. That way, if
we decide to use a different file, we only have to change the code in one place.

A modified version of Hangman with this code in it can be found in the file

06_02_hangman_file_try.py.
Reading Big Files
The way we did things in the previous section is fine for a small file containing some words. However,
if we were reading a really huge file (say, several megabytes), then two things would happen. First, it
would take a significant amount of time for Python to read all the data. Second, because all the data is
read at once, at least as much memory as the file size would be used, and for truly enormous files, that
might result in Python running out of memory.
If you find yourself in the situation where you are reading a big file, you need to think about how
you are going to handle it. For example, if you were searching a file for a particular string, you could
just read one line of the file at a time, like this: