The filesystem on your computer is like a tree made up of folders (also called "directories") and files. The filesystem has a root directory called
/, and everything on your computer lives in subdirectories of this root directory.
We often navigate the filesystem graphically by clicking on graphical folders. We can do the exact same navigation from the command line.
There are three commands that we'll be using at a command prompt to navigate the filesystem on your computer:
ls pwd cd
ls lists the contents of a directory.
pwd gives the full directory path to your current directory.
cd moves you into a new directory (it stands for "change directory").
Let's practice using these commands.
Starting a terminal varies between Linux distributions: it may be called Terminal on some and Konsole on others. If you have trouble starting, ask an instructor for help.
(that's an l the letter, not the number 1)
Type each of these commands and hit enter:
This lists all the files in your home directory.
This displays the full directory path to your current directory, which is your home directory.
This will change you into the / root directory.
This lists the contents of the / root directory.
This will change you into the Users subdirectory of the / root directory.
You should see a list of all the files in /Users, including the directory for your username -- your home directory.
This displays the full directory path to your current directory, /Users.
.. means "parent directory", so this command moved you up to the parent directory. You were in /Users, so now you are in /, the root directory.
This lists the contents of the root directory, confirming where you are.
You can use Tab to auto-complete directory and file names. So from inside the root directory /, if you type cd Us and hit Tab, the command prompt will auto-complete the directory name, and you can then hit enter to change into the /Users directory.
The command prompt maintains a command history. You can use the up arrow to cycle through old commands.
Answer these questions. Experiment at the command line if you need to! If you aren't sure about an answer, ask a helper.
You've practiced using
cd to navigate your computer's filesystem from the command prompt.
Insert the CD or USB drive provided by an instructor. In your file browser, drag the icon for the "workshop" folder onto your desktop to make your own copy of the class materials. Then you can remove the CD or USB drive and pass it along. If you can't use a CD or USB drive, download this file and have an instructor help you prepare it.
The Python programming language is "open-source" - no single person or company owns it, or can own it - it's for everyone to use. Some companies wrap it up together with useful related programs. We'll use one such packaging called Anaconda, published free of charge by Continuum Analytics, because that's the most reliable way to get everything we need installed.
Double-click the "workshop" folder you just copied to enter it, then enter the "linux" folder.
If your computer is 64-bit: Double-click "Anaconda-1.7.0-Linux-x86_64.sh".
If your computer is 32-bit: Double-click "Anaconda-1.7.0-Linux-x86.sh".
Ugh, you're already confusing me!: I know, "do you have a 64-bit computer" is not a beginner-level question! So try double-clicking "Anaconda-1.7.0-Linux-x86_64.sh". If that works, your computer is 64-bit, so go ahead and follow the 64-bit directions. If you get an error message saying something like "not supported by this processor", your computer is 32-bit, so follow those directions instead.
The installer will ask you several questions. In each case, accept the default answer - that is, do whatever the prompts suggest.
Start up a Terminal command prompt.
To start Python, type
at the command prompt and hit
enter. You should see something like
Python 2.7.1 (r261:67515, Feb 11 2010, 00:51:29) [GCC 4.2.1 (Apple Inc. build 5646)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>>
>>> indicates that you are at a Python prompt.
Exit the Python prompt by typing
enter. You can also use Ctrl+D to exit the Python interpreter. Now you're back at the Linux command prompt (which looks something like jesstess$).
What is the difference between a command prompt and a Python prompt? If you're not sure, ask a helper.
Practice these steps until you feel comfortable navigating to a command prompt, starting Python, and exiting Python.
On Linux, we suggest the GEdit text editor. GEdit should already be installed on your computer.
To start GEdit: click Applications, point to Accessories, and click Text Editor. If you don't have this option, let a staff member know.
If you prefer to start applications from a terminal, you can type the following into a terminal to launch GEdit:
That's it! Now, you can hit tab to indent your code, and that indentation will actually be made of spaces. This change will help you use spaces consistently, so that Python doesn't get confused about whitespace.
If you prefer a different editor for text, check with an instructor before moving on to make sure it will work for the weekend. vim users will probably want to add the lines
set tabstop=4 set softtabstop=4 set autoindent
to their .vimrc file.
Interactive Python programming at a Python prompt is great for short pieces of code and for testing ideas. For longer code, it can be easier to save the code in a file, and execute the contents of that file (aka a Python script). In this section, we'll practice running Python scripts.
Add the following line to your new text file:
print "Hello World!"
Save the script as hello.py in your home directory. The
.py extension indicates that this file contains Python code.
>>>. Make sure you are at a terminal prompt and not a Python prompt; if you are at a Python prompt, you can type
exit()on a line by itself and then hit
enterto exit Python and return to a terminal prompt.
hello.pyin the output of
enter. Doing this will cause Python to execute the contents of that script -- it should print "Hello World!" to the screen. What you've done here is run the Python application with an argument -- the name of a file, in this case "hello.py". Python knows that when you give it a file name as an argument, it should execute the contents of the provided file. You get the same result as if you typed
print "Hello World!"
at a Python prompt and hit
You created and ran your first Python script!
You'll spend most of this workshop using a Python tool called the IPython Notebook. This lets you run IPython cells, which are like the interactive Python prompt you tried out in Goal #3, right within your browser.
Open a Terminal (see Goal #1) and use
cd to navigate into the
Your browser should come up with a page called "IP[y]: Notebook". That's your IPython Dashboard; it has a list of notebooks. Click "notebook_practice" and follow the instructions on the notebook that it brings up.
Go back to the IPython Dashboard page in your browser, and click the "day1.1" notebook. Follow along through that tutorial. Remember to ask lots of questions, to the instructors and to the other students - we're all here to help each other!
After "day1.1", you'll go through "day1.2" and then part of "exercises". We'll leave the rest for tomorrow!