Python Programming Overview 1

Python Programming Overview 1

(1) OS supported by Python

Portability

• Python is supported on nearly every major OS, including Windows
• v2.7 installed by default by most Linux distribution (Debian, Ubuntu)
• Others OS
  • AS/400, BeOS, MorpOS, MS-DOS, OS/2, and more

Caveats

• There may be OS-specific caveats
• For example, on Windows: carriage returns are treated differently, as are file paths
• Permissions and file I/O are other things to watch out for

(2) Why Choose Linux?

Linux vs. Windows

• Not an OS debate
• Significant portion of Internet-facing servers run some form of UNIX
• Python first released for a UNIX-based OS

Today’s Technology

• If you wanted to use Linux at home, you either had to dual boot or un the OS exclusively
• Dual booting often a hassle
• With virtualization, barrier to entry is far lower, and almost no rist of data loss

“Easy” Linux Distributions

• Installing Linux used to be a pain; now way easier
• Easiest Linux Distros to install and use quickly
  • Ubuntu (Debian-based)
  • Linux Mint (Ubuntu-based)

(3) Installation & Virtual Environment

Libraries & Dependencies

• Like other languages, Python has a package management system
• Other languages got this right to begin with; Python has had some struggles with it
• “Standard” Python package manager is “pip”
  • Packages that pip installs are in PyPI, the Python Package Index.

Installation

• Python packages by default are installed system wide
• Makes dealing with version conflicts and dependencies a pain
• “virtualenv” is the solution

Virtualenv & virtualenvwrapper

• Virtualenv creates a virtual environment where a copy of python and pip are “copied” to, and any packages are localized to
• Can run any number of desired virtualenvs, each with its own set of installed packages
• Each virtualenv operates independently
• Virtualenvwrapper is a handy shell script that shortcuts many virtualenv functions for you
• Now you can install python packages without worrying about your system integrity
• Or conflicting package versions

(4) Excercises

• Python-pip, and virtualenvwrapper are already installed (Figure 1)
  • If you are running Linux, install pip for Python if it’s not already installed
  • After installing pip, use it to install virtualenvwrapper (should require root privileges)
  • Set up virtualenvwrapper and create a new virtualenv called “test”
  • Automatically put you inside the virtual environment you just created (test)
    • From here all actions are localize inside the virtual environment
• Virtualenvs create new virtual environment in your home directory (Figure 2)
  • hidden directory “.virtualenvs”
• Install pip inside the virtual environment (Figure 3)
  • Run python inside virtualenvs
  • Try to do HTTP request and check the HTTP response
• Look up JSON object using “r.json()” (Figure 4)
  • There is no JSON object
• Look up HTML object using “r.text” (Figure 5)
  • There is no JSON object
• Exit from virtual environment “deactivate” (Figure 6)
  • Import request: no such module
    • pip was not installed, and module was not copied
  • List virtualenv “lsvirtualenv”
    • Go in test virtualenv “workon test”
• To set an environment variable everytime, register the path in the .bashrc file (Figure 7)
  • virtualenvwrapper.sh
• Or run the script by typing the full path (Figure 8)
  • /usr/local/bin/virtualenvwrapper.sh