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What to expect from this tutorial

give a woman a fish and you feed her for a day; teach a woman to fish and you feed her for a lifetime

We will not write much Python code today. Instead, we will make sure that everyone has important tools installed, which will enable you to write a lot of Python code in the future!

The tools for today are: Python, virtualenv, Atom and ipdb.

This is the plan

• Introduction
• A Command-Line Crash Course
• Install Python 2.7
• Starting Python from the Terminal
• Install Virtualenv & Virtualenvwrapper
• Install & configure Atom.io editor
• Create your first Python program
• Debugging

Introduction

• No one can learn programming in a day
  • or in a week
  • or in a month
  • or in a year
• If you want to become really good
  • you have to try things yourself
  • you should find a mentor or a user group to guide you
• This tutorial is just a tiny step into the right direction
• I hope that
  • it empowers you to take more steps on your own
  • you will come back for more :)

Follow along

• You can open this presentation in your browser and follow along
• Open: mbrochh.github.io/python-introduction

This is the plan

• Introduction
• A Command-Line Crash Course
• Install Python 2.7
• Starting Python from the Terminal
• Install Virtualenv & Virtualenvwrapper
• Install & configure Atom.io editor
• Create your first Python program
• Debugging

A Command-Line Crash Crouse

• The command line is a window where you can execute text-commands
• On Windows it is called "PowerShell"
• On OSX and Ubuntu it is called the "Terminal"
• For simplicity, we will always call it the "Terminal"

Windows: The PowerShell

• Open the Start-menu and search for "PowerShell"
• You might want to drag it onto your Desktop
• You will open this A LOT

OSX & Ubuntu: The Terminal

• Open your computer search
• That's Spotlight on OSX (press COMMAND+SPACE)
• That's the Ubuntu icon at the top of the sidebar
• Search for "Terminal"

Your Home Folder

• Type pwd into the terminal:

  pwd
  

• It will show which folder you are currently in
• For a newly opened terminal, that is your home folder
• Your home folder is also called "~" (tilde)
• No matter where you are, you can type cd ~ to get into your home folder

  cd ~
  

• By the way: pwd stands for print working directory

List The Current Folder

• Hint: "folder" and "directory" is the same
• I say folder, because it's shorter to write :)
• Type ls to list the content of the current folder

  ls
  

• By the way: ls stands for list

Move into another folder

• Press TAB to autocomplete things
• Type cd ~/Documents to move into the Documents folder in your home directory

  cd ~/Documents
  

• By the way: cd stands for change directory

Create a new folder

• Type cd ~ to move into your home folder

  cd ~
  

• Type mkdir Projects to create a new folder called "Projects"

  mkdir Projects
  

• How about creating a folder for our first project as well?
• Type cd ~/Projects and then mkdir test

  cd ~/Projects
  mkdir test
  

• By the way: mkdir stands for make directory

Create a new file

• Type cd ~/Projects/test to move into your test project folder

  cd ~/Projects/test
  

• On OSX/Ubuntu, type touch test.py to create a new file called "test.py"

  touch test.py
  

• On Windows, type echo $null >> test.py

  echo $null >> test.py
  

• So sorry, Windows doesn't have a nicer command for creating files :(
• Type ls to see if your new file is there

  ls
  

High-Five!

• This is just the tip of the iceberg
• But it will get you through this tutorial :)
• Whenever you see black boxes with commands in these slides, it means you should type something into your terminal:

  black boxes like this
  

This is the plan

• Introduction
• A Command-Line Crash Course
• Install Python 2.7
• Starting Python from the Terminal
• Install Virtualenv & Virtualenvwrapper
• Install & configure Atom.io editor
• Create your first Python program
• Debugging

Install Python on OSX

# Hint: You don't need to do this!
# This is just an tip for the future.
brew install python

Install Python on Windows

Install Python on Ubuntu

sudo apt-get update && sudo apt-get upgrade

sudo apt-get install python-dev
sudo apt-get install python-pip

This is the plan

• Introduction
• A Command-Line Crash Course
• Install Python 2.7
• Starting Python from the Terminal
• Install Virtualenv & Virtualenvwrapper
• Install & configure Atom.io editor
• Create your first Python program
• Debugging

Starting Python on OSX & Ubuntu

python

exit()

Starting Python on Windows

pip install pyreadline
pip install ipdb

python

exit()

Important Hint

This is the plan

• Introduction
• A Command-Line Crash Course
• Install Python 2.7
• Starting Python from the Terminal
• Install Virtualenv & Virtualenvwrapper
• Install & configure Atom.io editor
• Create your first Python program
• Debugging

Install Virtualenv on OSX & Ubuntu (I)

Virtualenv helps to keep each environment for each project clearly separated

# On OSX,
# On Ubuntu you did this in an
# earlier slide already
sudo easy_install pip

sudo pip install virtualenv

sudo pip install virtualenvwrapper

Install Virtualenv on OSX & Ubuntu (II)

echo "export WORKON_HOME=~/Envs" >> ~/.bash_profile
echo "source /usr/local/bin/virtualenvwrapper.sh" >> ~/.bash_profile

echo "export WORKON_HOME=~/Envs" >> ~/.bashrc
echo "source /usr/local/bin/virtualenvwrapper.sh" >> ~/.bashrc

Install Virtualenv on Windows

pip install virtualenvwrapper-win

What is this pip thing?

• pip is a program that is written in Python
• It allows you to download and install other programs which are also written in Python
• You can search for available Python programs atwarehouse.python.org

Using Virtualenv

mkvirtualenv test

deactivate

workon test

cd ~/Envs/test

This is the plan

• Introduction
• A Command-Line Crash Course
• Install Python 2.7
• Starting Python from the Terminal
• Install Virtualenv & Virtualenvwrapper
• Install & configure Atom.io editor
• Create your first Python program
• Debugging

Install & configure Atom.io editor

Install flake8 globally

This is to make sure that "linter-flake8" works

Open a Terminal and execute:

# On Windows
pip install flake8

# On OSX & Ubuntu
sudo pip install flake8

What is this flake8 and linter thing?

• A linter is a program that checks if the code of another program looks pretty
• flake8 is a Python program that is able to lint your Python code for you.
• There are many more linters, basically every programming language has it's own.
• If you want to learn how Python code should be written grab some popcorn and read the famous PEP008 Not now! It's a long read ;)

Starting Atom

cd ~/Projects/test

atom .

Important shortcuts

• COMMAND+\: Show project files
• COMMAND+P: Open any file
• COMMAND+F: Search & replace in current file
• COMMAND+SHIFT+F: Search & replace in whole project
• CONTROL+ALT+O: Show symbols tree view
• COMMAND+S: Save file
• COMMAND+SPACE: Call auto-complete
• COMMAND+,: Open settings
• COMMAND+W: Close tab
• COMMAND+TAB: Open next tab
• COMMAND+SHIFT+TAB: Open previous tab

Hint: On Windows & Ubuntu, COMMAND is CONTROL

This is the plan

• Introduction
• A Command-Line Crash Course
• Install Python 2.7
• Starting Python from the Terminal
• Install Virtualenv & Virtualenvwrapper
• Install & configure Atom.io editor
• Create your first Python program
• Debugging

Your first Python program!

• Open the first chapter of Learn Python The Hard Way

• Let's create a folder for all the exercises of the book:

  cd ~/Projects
  mkdir lpthw
  cd lpthw
  
  # On OSX/Ubuntu:
  touch ex1.py
  
  # On Windows:
  echo $null >> ex1.py
  

• Start Atom:

  atom .
  

Don't give up!

This is the plan

• Introduction
• A Command-Line Crash Course
• Install Python 2.7
• Starting Python from the Terminal
• Install Virtualenv & Virtualenvwrapper
• Install & configure Atom.io editor
• Create your first Python program
• Debugging

Debugging your program

• This is an advanced topic
• We will not have enough time to train this during the workshop
• I'm putting this into the slides because it is the last crucial tool that you need for real software development

• Instal ipdb

  # On OSX/Ubuntu:
  sudo pip install ipdb
  
  # On Windows:
  pip install ipdb
  

Place a breakpoint into your code

• When debugging programs, you place so called breakpoints
• For Python, you need to paste this into your code:

  import ipdb; ipdb.set_trace()
  

• Luckily, Atom has a plugin for this, so you can just press F7 at the position where you want the breakpoint.
• When you are done, press SHIFT+F7 to remove all breakpoints

Now run your program

• After placing the breakpoint, run your program as usual

  python your_filename.py
  

• Instead of executing normally, the program will stop at your breakpoint
• Now you have all the time in the world to inspect your variables
• You can also move to the next line in the program one step at a time

How to use ipdb

• When you are inside of the ipdb debugger:
• Press ? to get all possible commands
• Press ? bt to get help for the bt command
• l: Shows the current line
• bt: Shows the full stack trace
• n: Jumps to the next line
• a: Shows all arguments of the current function
• c: Continue execution until the program ends
• Type in a variable name to see it's value
• You can even change variables and continue the program

Recap

• Python is already installed on OSX & Ubuntu
• It's easy to install on Windows
  • Make sure to extend PATH environment variable
• Atom editor can be installed easily
• When you start a project:
  • Just create a folder
  • Then create a virtual environment
  • Create a "*.py" file inside that folder
  • Run "atom ." inside that folder
  • Execute your program and debug it using the Terminal

What next?

• Learn the Python language
  • Learn Python The Hard Way is a fantastic free book
• Learn to use all features of Atom
  • Memorize important keyboard shortcuts
  • Lean to use the vim-mode plugin
• Learn to use your Terminal
• Learn how to use git and GitHub
• Find a small pet project for yourself and just do it!

Stay in touch!

• Join our Slack community at pyladies-sg-slackin.herokuapp.com
• Follow PyLadies Singapore on Facebook
• Follow @PyLadiesSG on Twitter
• Follow Python User Group Singapore on Facebook
• Join the Python User Group Singapore Meetup community
• Visit PyCon Singapore 2016 next year in June!