title:	Beginner's Workshop 3
Author:	Alexander Loechel
event:	PyLadies Munich - Beginner's Workshop
keywords:	Python, PyLadies, Workshop
data-transition-duration:	1500
css-all:	css/workshop3.css
auto-console:	Yes

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class:	slide title-slide centered level-1
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Welcome to

Beginner's workshop 3

Theory of data flow and data control

Note

Test Note

id:	recap-ws1
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Recap Workshop 1

Introduction
What is Python
- About the Language
- History and Background
Basic Philosophy - The Zen of Python
Tools and Setup
- Python Interpreter
- Virtual Environments
- pip & easy_install
Hello World example

id:	syslab
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Syllabus of the planned curriculum

Workshop 1 - Introduction, Setup and first steps (February 26th 2015)
Workshop 2 - Theory of data types and data structures
For beginners, March 12th 2015)
Workshop 3 - Theory of data flow / data contol
(For beginners, April 1nd 2015)
Workshop 4 - Repeating Workshop
(For beginners and language changer, April 16th 2015)
Workshop 5 and ongoing:
More specialized on your preferred direction: web-development and data

up to 8-12 Workshops

id:	recap-ws2-1
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data-x:	r+1000
data-y:	1000

Recap Workshop 2

Theory of data types and data structures

Paradigms
all programming languages have the same power (turing complete)
Data types - Duck Typing

Smart data structures and dumb code works a lot better
than the other way around

—Eric Raymond
- Objects - Everything is an object in Python
- Primitive data types
- Composite types

id:	recap-ws2-2
class:	slide level-1
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Recap Workshop 2

Theory of data types and data structures

Module / Module Hierarchy
Compiler and interpreter
Unix Philosophies
- Write programs that do one thing and do it well.
- Write programs to work together.
- Write programs to handle text streams,
  because that is a universal interface.
—Doug McIlroy

id:	recap-ws2-3
class:	slide level-1
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Recap Workshop 2

Theory of data types and data structures

Standard type Hierarchy and type()-Function
Mutable and Immutable Types
Numbers
- Integrals (Booleans & Integers) - Boolean Operations
- Real (floating point)
- Complex

id:	recap-ws2-4
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Recap Workshop 2

Theory of data types and data structures

Sequences, Sets and Mappings
- Tuples ((value1, value2, ...))
- Strings (Unicode (Python2 u'' ) & Byte (Python3 b'' ) )
- Lists ([])
- Set & Frozenset
- Dict ({ 'key': 'value', ... })
Callable types
- Classes
- functions and methods
Modules

id:	intro-python
class:	slide level-1
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Introduction to Python

1 # Python 3: Fibonacci series up to n
2 def fib(n):
3     a, b = 0, 1
4     while a < n:
5         print(a, end=' ')
6         a, b = b, a+b
7     print()
8 fib(1000)

Important parts we see

method definition def fib(n)
variables a, b
discrete values 0, 1, 1000
data flow / control element for a loop: while
method calls print() & fib()

id:	base-1
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Basic Elements of
data flow / data control

Simple statements
- Expression statements
  - True, 'text',
  - boolean / comparison operations a == b
  - List comprehension [x.id for x in my_list]
  - objects or procedures
- Assignment statements (x = y)
- Augmented Assignment Statements (text += 'some text')
- special simple statements with a meaning in context
  (pass, return, yield, raise, break, continue, import)

id:	base-2
class:	slide level-1
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Basic Elements of
data flow / data control

Compound statements
- Control flow statements
  - conditional switches (if ... elif ... else)
  - loops (while & for ... in ...:)
    important here: iterators & generators
- Exception handling (try: ... except: ... finally: ...)
- Context Managers (with)
- Definition statements (class, def) and calls call()

id:	class-def
class:	slide level-1
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Definition Statements and Calls

everything in Python is an Object

 1 import modul
 2 
 3 class MyClass(inheritance1, inheritance2):
 4 
 5     def __init__(self, param):
 6         self._param = param
 7 
 8     def get_param(self):
 9         return self._param
10 
11     def set_param(self, param):
12         pass
13 
14 my_obj = MyClass('value')
15 print(my_obj.get_param())

id:	ifthen
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Conditional Switch

Classic if then else

if a == 0:
    expression
elif a > 0 and a < 10:
    expression
elif a < 0:
    expression
else:
    expression

Base

Truth evaluation of values and Operations (Boolean, Comparison, Shifting, ... Operations)

Test via `bool(expression)`

id:	bools1
class:	slide level-1
data-x:	r+0
data-y:	r+1000

Boolean Operations

>>> True and True
True
>>> True or False
True
>>> not False
True

id:	bools2
class:	slide level-1
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Comparison Expressions

>>> 1 > 0
True
>>> ' text '.strip() == 'text'
True
>>> result = None
>>> result is not None
False
>>> 11 in range(5)
False

id:	bools3
class:	slide level-1
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Truth Value of expressions

>>> # An empty sequence has a Truth-Value of False
>>> # A sequence with content has a Truth-Value of True
>>> my_list = []
>>> if not my_list:
>>>    print('List is empty')
'List is empty'

>>> # NoneType has a Truth-Value of False
>>> return_value = function_call()
>>> # if return_value is None
>>> if return_value:
>>>     return_value.start()

id:	loops
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Simple Loops

Simple for loop

for index in list:
    print(index)

Simple while loop

index = 1
while index <= 100:
    print(index)
    index += 1

id:	aloops1
class:	slide level-1
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data-y:	r+1000

Advanced for Loop

>>> for fruit in ['banana', 'apple', 'orange']:
>>>     print(fruit)
>>> else:
>>>     print('no more fruits available.')
banana
apple
orange
no more fruits available.

id:	aloops2
class:	slide level-1
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data-y:	r+1000

Advanced for Loop & Context Manager

 1 with open(file, 'r')  as input_file:
 2     line_number = 0
 3     for line in input_file.readlines():
 4         line_number += 1
 5         if line == 'Appendix':
 6             break
 7         elif line.startswith('#'):
 8             # Line starts with comment sign: ignore and continue
 9             continue
10         print(line)
11     else:
12         print('No Appendix found')
13     print('We have read {lines}'.format(lines=line_number))

with indicates a Context Manager - means that specific operations are automatically applied on exit of context here the file is closed
break quites the loop before the normal ending condition of the loop is reached
continue indicates that all following expressions in the loop is not executed and next loop circle starts
else is only executed if no break statement has quite the loop

id:	iter-gen
class:	slide level-1
data-x:	r+1000
data-y:	1000

Iterator

you can only loop (for ... in ... :) over a sequence-like object
sequences implements a __next__() method
everything that behaves like a sequence and implements a __next__() method is iterable

id:	gen
class:	slide level-1
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Generator

 1 import time
 2 
 3 def my_takt_generator():
 4     num = 1
 5     while True:
 6         yield num
 7         num = num % 4 + 1
 8 
 9 takt = my_takt_generator()
10 
11 counter = 0
12 for takt_elem in takt:
13     print(takt_elem)
14     counter += 1
15     if counter >= 60:
16         break
17     time.sleep(1)

counts 1 2 3 4 1 2 3 4 ...

id:	async
class:	slide level-1
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AsyncIO Generators

1 class DistanceSensor(Sensor):
2 
3     @asyncio.coroutine
4     def get_distance(self):
5         while true:
6             distance = yield from self._messure_distance()
7             if distance < 100:
8                 print('Warning Distance too low')

id:	exceptions
class:	slide level-1
data-x:	r+1000
data-y:	1000

Exceptions & Exception Handling

 1 def div(value1, value2):
 2     if value2 == 0:
 3         raise ZeroDivisionError
 4     return value1 / value2
 5 
 6 try:
 7     value1, value2 = 10, 0
 8     print(div(value1, value2))
 9 except Error as e:
10     print('something went totally wrong')
11     print(e.message)

id:	try
class:	slide level-1
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All following explanations and examples are practical session

please open your
IPython Notebook http://localhost:8888/

id:	next-meeting
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Next Workshop

Thursday April 23th 2015 18:30 ???

Repeating Workshop - Exercises

id:	overview
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data-y:	2500
data-scale:	8

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workshop3.rst

workshop3.rst

Recap Workshop 1

Syllabus of the planned curriculum

Recap Workshop 2

Theory of data types and data structures

Recap Workshop 2

Theory of data types and data structures

Recap Workshop 2

Theory of data types and data structures

Recap Workshop 2

Theory of data types and data structures

Introduction to Python

Important parts we see

Basic Elements of
data flow / data control

Basic Elements of
data flow / data control

Definition Statements and Calls

Conditional Switch

Base

Test via `bool(expression)`

Boolean Operations

Comparison Expressions

Truth Value of expressions

Simple Loops

Simple for loop

Simple while loop

Advanced for Loop

Advanced for Loop & Context Manager

Iterator

Generator

AsyncIO Generators

Exceptions & Exception Handling

Next Workshop

Files

workshop3.rst

Latest commit

History

workshop3.rst

File metadata and controls

Recap Workshop 1

Syllabus of the planned curriculum

Recap Workshop 2

Theory of data types and data structures

Recap Workshop 2

Theory of data types and data structures

Recap Workshop 2

Theory of data types and data structures

Recap Workshop 2

Theory of data types and data structures

Introduction to Python

Important parts we see

Basic Elements of data flow / data control

Basic Elements of data flow / data control

Definition Statements and Calls

Conditional Switch

Base

Test via bool(expression)

Boolean Operations

Comparison Expressions

Truth Value of expressions

Simple Loops

Simple for loop

Simple while loop

Advanced for Loop

Advanced for Loop & Context Manager

Iterator

Generator

AsyncIO Generators

Exceptions & Exception Handling

Next Workshop

Basic Elements of
data flow / data control

Basic Elements of
data flow / data control

Test via `bool(expression)`