Before we do anything, we need to understand some of the components we'll be interacting with and switching between.
The Python interpreter: we input commands, define variables and functions, write loops, etc. The interpreter parses it all for us, line by line as we write them, and takes action.
Text editor: this is where we essentially chain a bunch of commands together within a single document and save it as a Python script (ending in .py).
The command line: Accessed via "Terminal" on OS X or "cmd.exe" (or possibly PowerShell) on Windows. It's where we run the Python interpreter, among other programs, and issue commands that allow us to navigate our computer's folders.
That's pretty much it. These three pieces give you a container for code you're writing, the program to run it and a method to get it all running. We'll be doing some switching back and forth between entering code directly into the interpreter we run from the command line and the text editor.
As we progress, we'll be dealing with two other things.
External libraries: Python comes with a standard library that has a ton of useful stuff. Developers have written libraries that take this functionality even further. By importing parts of these libraries into our Python script, we can do complex things, like fetch a web page, with a single line of code.
A virtual enviroment: The bubble where all of our code lives.
This is a crash course in some of Python's major data types and and how to tame them. We'll be doing things like mashing strings together, running through items in a list and defining very simple functions.
We'll be using iPython's interactive interpreter, which means we have access to a few extra features (which iPython modestly calls magic functions).
The files in this folder:
var.py: A Python script with some variables of different types like integers, lists and dictionaries.
exercises.py: A file that gives a list of exercises in the form of comments; guidance on how to manipulate the variables in var.py. It's also the place we can write code to save for future reference. Nearly everything we do in this task will use iPython.
fun_with_subs.py: A file for practicing string substitutions, which is something we'll be doing frequently. It covers the depreciated method you'll encounter frequently and covers
whitespace.py: A guide to how Python decides which blocks of code to run when; it's all controlled by indentation.
Any finished versions will appear in the completed folder.
Opening iPython is as easy as typing
ipython into PowerShell.
To get everything from var.py queued up, we can either run it from within iPython using one of the magic functions:
Or we can use the more traditional method of importing everything defined in a script, treating it as a module:
from var import *
This will make a little more sense as we start bringing in other Python libraries to tackle our other tasks. Either way, it's going to get us those variables defined in var.py. We can quickly test that these variables were loaded by typing
Let's say I have a longer chunk of code that I want to try out in iPython to see if it works as expected.
presents = ['A brand new car', 'Socks'] for gift in presents: if gift == 'A brand new car': print gift, '<- Oh yeah!' else: print gift, '<- Meh.'
Having to type this line by line into the interpreter and pay attention to indentation can be a pain.
But I can write that block of code in a text editor instead, then select it all and copy it. Switching over to iPython, I can use the built-in paste function:
This will paste the contents of my clipboard, preserving all the indentation and other white space, and execute whatever code was there. Pretty handy.
Finally, iPython has another function that will give you a recap of commands you've typed: