#!/usr/bin/env python
# coding: utf-8
# Introduction to Python (1)
# ===
#
# About Python
# ===
#
# History
# ---
#
# * Created early 90's by Guido van Rossem at CWI.
# - Name: Monty Python.
# * General purpose, high-level programming language.
# * Design is driven by code readability.
# About Python
# ===
#
# Features
# ---
#
# * Interpreted, no separate compilation step needed.
# * Imperative and object-oriented programming.
# - And some functional programming.
# * Dynamic type system.
# * Automatic memory management.
#
# We'll come back to most of this.
# About Python
# ===
#
# Why Python?
# ---
#
# * Readable and low barrier to entry.
# * Rich scientific libraries.
# * Many other libraries available.
# * Widely used with a large community.
# About Python
# ===
#
# Python 2 versus Python 3
# ---
#
# * Python 3 is backwards incompatible.
# * Some libraries don't support it yet.
# * Python 2.7 is the last Python 2.
# * Some Python 3 features are backported in Python 2.7.
# * Default Python on most distributions is Python 2.7.
#
# We use Python 2.7 for the time being.
# Running Python code
# ===
#
# Two main ways of writing and executing Python code.
#
# Interactively
# ---
#
# * Statement by statement directly in the interpreter.
#
# Non-interactively
# ---
#
# * By editing in a file and running the code afterwards.
# We'll start with the first option.
# Running Python code
# ===
#
# The standard Python interpreter
# ---
#
# Start it by typing `python` on the command line:
#
# $ python
# Python 2.7.3 (default, Jan 2 2013, 13:56:14)
# [GCC 4.7.2] on linux2
# Type "help", "copyright", "credits" or "license" for more information.
# >>>
#
# * It shows an interpreter prompt.
# * You can give it Python code to interpret.
# Running Python code
# ===
#
# The IPython interpreter
# ---
#
# * Similar to the standard Python interpreter, but with
# * syntax highlighting,
# * tab completion,
# * cross-session history, etcetera...
#
# Start it by typing `ipython` on the command line:
#
# $ ipython
# Python 2.7.3 (default, Jan 2 2013, 13:56:14)
# Type "copyright", "credits" or "license" for more information.
#
# IPython 0.13.1 -- An enhanced Interactive Python.
# ? -> Introduction and overview of IPython's features.
# %quickref -> Quick reference.
# help -> Python's own help system.
# object? -> Details about 'object', use 'object??' for extra details.
#
# In [1]:
# From now on, play along in your own IPython interpreter.
# Python as a calculator
# ===
#
# Integers
# ---
# In[1]:
17
# In[2]:
(17 + 4) * 2
# Python as a calculator
# ===
#
# Floating point numbers
# ---
# In[3]:
3.2 * 18 - 2.1
# In[4]:
36. / 5
# Scientific notation:
# In[5]:
1.3e20 + 2
# In[6]:
1.3 * 10**20
# Python as a calculator
# ===
#
# The division operator
# ---
# In[7]:
35 / 5
# Division is a bit weird: if you give it integer arguments, the result will also be an integer.
# In[8]:
36 / 5
# Python as a calculator
# ===
#
# The division operator
# ---
# In[9]:
35 / 5
# In[10]:
36 / 5
# Solution 1
# ---
#
# Give floating point arguments instead of integer arguments.
# In[11]:
36. / 5.
# Python as a calculator
# ===
#
# The division operator
# ---
# In[12]:
35 / 5
# In[13]:
36 / 5
# Solution 2
# ---
#
# From Python 3 onwards, division behaves differently. You can actually get that behaviour in Python 2.7:
# In[14]:
from __future__ import division
36 / 5
# Variables
# ===
#
# * We can use names to reference values (variables).
# * No need to declare them first or define the type.
# In[20]:
a = 1.3e20
b = 2
# In[21]:
a
# In[28]:
c = a + 1.5e19 * b
c * 2
# Python's type system (1/4)
# ===
#
# Every value has a type, view it using `type`:
# In[18]:
type(27)
# In[19]:
type(3.0 * 2.7)
# In[20]:
type(a)
# Python's type system (2/4)
# ===
#
# Another example of a builtin datatype is `str`, we'll see more later:
# In[21]:
type('I am a homo sapiens')
# Some operations are defined on more than one type, possibly with different meanings.
# In[22]:
'beer' * 5 + 'whiskey'
# Python's type system (3/4)
# ===
#
# Dynamic typing means that variables can be assigned values of different types during runtime.
# In[9]:
a
# In[10]:
type(a)
# In[5]:
a = 'spezi'
type(a)
# Python's type system (4/4)
# ===
#
# Python is strongly typed, meaning that operations on values with incompatible types are forbidden.
# In[24]:
'beer' + 34
#
#
Hands on!
#
#
# - We’ve seen that b = 2 is legal.
#
# - What about 2 = b?
# - How about a = b = 1?
#
#
# - In math notation you can multiply x and y like this: xy.
# What happens if you try that in Python?
# - How many seconds are there in 42 minutes and 42 seconds?
# - How many miles are there in 16 kilometers? Hint: there are 1.61 kilometers in a mile.
# - Let's assume that you run a 42 kilometer race in 4 hours 42 minutes and 42 seconds.
#
# - What is your average pace (time per mile in minutes and seconds)?
# - What is your average speed in miles per hour?
#
#
# - Use string operations to reference string 'tra la la la' in a variable named song.
# - If an article costs 249 Euros including the 19% Value Added Tax (VAT), what is the actual VAT amount in Euros for the corresponding article?
#
#
#