Unix help

Contents:

Python FAQ

How do I find out whether a graph is bipartite?
For the coursework, you don't need NetworkX to determine this. Just looking at the data should be enough to determine which one is bipartite and which one is not.
If you are using NetworkX, keep in mind that the is_bipartite() function has different results depending on whether the graph is directed or not.

Why do I not see any output when I execute a script whereas it works fine using the interpreter?
The interpreter automatically prints results. For example, if you type "N(pi)" the interpreter prints the value of pi. If you do the same in a script, there will be no output. In order to see output from a script you need to print it ("print N(pi)").

There seem to be several possible answers for some of the questions about data analysis in the coursework
That is correct. You need to decide which representation is more interesting.

Why are there funny characters on the screen?
The command "sys.displayhook = pprint" uses UTF-8 characters to display mathematical formulas in a nicer format. Unfortunately, this does not always work perfectly when the client is on a PC and the server is Unix. To disable the display hook command temporarily, type
sys.displayhook = sys.__displayhook__
To disable the command permanently, delete that line from your .pythonstartup file.

Why are my commands for sets not working properly
You'll need from sets import Set for the exercises to work properly. Otherwise, you would be using the sets module from SymPy, which is different from the one in Python.

Why is this code not working even though nothing seems wrong?
Are you maybe reusing a name which is predefined by Python or by your program? You may not be getting a warning if you are overwriting a predefined name or if you are using the same name for a function and a variable, etc, but your code won't work.

Installing Python on your own computer

You can login to the university server remotely (see below). Therefore it should not be necessary for you to install Python on your own computer. If you do want to run it yourself, make sure that you have a version after 2.4 (for example, Python 2.6.4). I have not tested any code on Python 3 yet. Python is pre-installed on Mac OS X and Linux computers. For PCs you can get it from: Python downloads.
You also need SymPy for most of the exercises.

Using your i-drive/DCS

General instructions on using Python on DCS.

You can edit the files on the I:-drive using Notepad++ or UltraEdit because the I:-drive provides access to the same files as the ssh window. Don't use plain Notepad, Word or WordPad. If you do not have an I:-drive, you need to map it: Go to All Programs -> School of Computing -> Unix -> Map Unix drives.

Unix editor: pico

Arrow keys etc: Use the arrow keys to repeat a previous command. Use the tab key to complete a filename.

In pico, you can use Ctrl-K to delete/cut a line and Ctrl-U to get it back (paste). You can cut/uncut several adjacent lines in one go.

Connecting from a home computer

A secure shell (SSH) client is needed. On Linux and Mac OS X, such a client is usually pre-installed (type "ssh" at the command-line). For PCs there are several clients freely available for download, such as PuTTY or a GUI ftp client such as WinSCP. The address for the server is socweb3.napier.ac.uk.

Some general Unix commands

Change to mydirectory	cd mydirectory
Create newdirectory	mkdir newdirectory
Remove (delete) olddir	rmdir olddir
Move (rename) olddir to newdir	mv -i olddir newdir
Show name of current dir.	pwd
Allow others to read and execute files in current directory	chmod go+rx .
List files in current dir.	ls
List all (incl. hidden)files, with details	ls -la
Show contents of myfile	more myfile
Move (rename) oldfile to newfile	mv -i oldfile newfile
Copy origfile to duplicatefile	cp -i origfile duplicatefile
Remove (delete) oldfile	rm -i oldfile
Allow others to read/change sharedfile	chmod go+rw sharedfile
Show the first few lines of largefile	head largefile
Show the last few lines of largefile	tail largefile
Edit a text file	nano or emacs or vi or pico
Find commands related to keyword	man -k keyword
Read manual for command	man command
Find true name of cmd	which cmd
Show environment variables	printenv
Change environvariable	setenv environvariable value