STARTING WITH PYTHON3 – The very beginning – part 2

Journal: uffmm.org,
ISSN 2567-6458, July 9, 2019
Email: info@uffmm.org
Author: Gerd Doeben-Henisch
Email:
gerd@doeben-henisch.de

CONTEXT

This is the next step in the python3 programming project. The first step can be found here. The overall context is still the python Co-Learning project.

PROGRAMMING TOOLS

First SW-tools to use for programming

In this second session we extend the overview of the possible programming tools, how they are interrelated, and how they work.

In the figure above you can see the windows 10 operating system as the root system for everything else. The win10 system communicates with the PATH-variable and uses this information for many operations. How on can edit this variable has been shown in the last session.

One can activate directly from the win10 system the power-shell with a command-line interface. Entering the right code one can activate from the power-shell either directly a python-shell for python commands or one can activate other programs like the editor ‘notepad’ or ‘notepad++’. With such editors one can edit python scripts, store them, and then run these scripts from the power-shell by calling a python-shell with these scripts as arguments (as shown in the first session).

The python shell allows the direct entering of python commands and gives immediately feedback whether it works and how. Therefore one calls this an interactive shell which is very handy to check quickly some commands and their effects.

Another tool, which we will use in this session, is the integrated script environment (IDLE). This is like the python-shell but with some additional functionalities (see below). The main usage is for editing larger python scripts with a built-in editor and for running these scripts.

THE IDLE TOOL

To use this new tool you can press the windows button to see the list of all apps (programs) available on your computer. Under ‘P’ you will find python 3.7.3 and within python you will find an entry for IDLE. By selecting this item and clicking on the right mouse-button you can select the option to attach this icon to the task bar. If it is there you can use it.

If you start the IDLE tool by clicking on the icon from the task bar it opens as a new python interactive shell with some more options.

A first thing you can do is to ask for the actual path you are in. For this you have to import the python module ‘os’ (operating system) and use the command ‘getcwd()‘ from this module. Entering ‘os.getcwd()‘ in the python command line generates the actual path as output on the next line.

>>> import os
>>> os.getcwd()
‘C:\\Users\\gerd_2\\AppData\\Local\\Programs\\Python\\Python37-32’
>>>

This reveals that the actual path is pointing to the location of the python exe module (on my pc). This is not what I want because I have created in the first session a folder with name ‘code’ in my home directory ‘\Users\gerd_2’. From inside of the IDLE tool it is not possible to change the actual path.  But python as language provides lots of options to do this. One option is described below:

The module os offers several functions. Besides the function ‘os.getcwd()’ which we have used already there is another command ‘os.chdir(pathname)‘. But to directly change the actual path one has to be cautious because the path ‘C:\\Users\gerd_2\code‘ includes the ‘\’-sign, this cannot be read directly by the os.chdir() command. You can surround this problem by using the ‘\’-sign twice: first as an ‘escape sign’ and then as the ‘object sign’, resulting in the following command format: ‘C:\\Users\\gerd_2\\code‘. Entering this nothing is given as a result, and when you repeat the question ‘os.getcwd()’ you will receive as new answer the new path. Here the dialog with the python-shell:

Python 3.7.3 (v3.7.3:ef4ec6ed12, Mar 25 2019, 21:26:53) [MSC v.1916 32 bit (Intel)] on win32

Type “help”, “copyright”, “credits” or “license()” for more information.

>>> import os

>>> os.getcwd()

‘C:\\Users\\gerd_2\\AppData\\Local\\Programs\\Python\\Python37-32’

>>> os.chdir(‘C:\\Users\\gerd_2\\code’)

>>> os.getcwd()

‘C:\\Users\\gerd_2\\code’

>>>

You can see that the python command ‘os.getcwd() has been used twice. If you want to repeat some command you can call-back the command history of the python-shell with the keystrokes ‘ALT+P‘. This recalls the past (P) of the command history.

Comment: In the command

>> os.chdir(‘C:\\Users\\gerd_2\\code’)

I have used the back-slash sign ‘\’ twice to make the string fit as argument for the ‘os.chdir()’ command. As one can learn does python allow another solution, which looks like this:

>> os.chdir(r’C:\Users\gerd_2\code’)

The solution is to use an additional ‘r’ directly before the string ‘…’ telling the python interpreter that the following string has to be understood as a raw string. This works, try it out 🙂

IDLE AND EXECUTION OF A SCRIPT

Now if we are in the target folder for my scripts we can look to all files which are in this folder actually. For this we can use the python command ‘os.listdir()’:

>>> os.listdir()

[‘savesrc.txt’, ‘script1.py’, ‘script1.pyw’, ‘script1b.py’, ‘showargs.py’, ‘threenames.py’, ‘tst1.py’, ‘what.py’, ‘what2.py’, ‘__pycache__’]

>>>

You can detect in this list the python script ‘scrpt1.py’. Entering the name of this script either with .py extension or without will not enable an execution:

>>> script1.py

Traceback (most recent call last):

File “<pyshell#6>”, line 1, in <module>

script1.py

NameError: name ‘script1’ is not defined

From the first session we know that we can start the script within the power-shell directly. For this we have to activate the powershell, have to go into the desired folder ‘code’ …

PS C:\Users\gerd_2> cd code

PS C:\Users\gerd_2\code> dir

Verzeichnis: C:\Users\gerd_2\code

Mode LastWriteTime Length Name

—- ————- —— —-

d—– 04.07.2019 19:03 __pycache__

-a—- 01.07.2019 18:44 182 savesrc.txt

-a—- 01.07.2019 18:41 92 script1.py

-a—- 24.06.2019 23:23 126 script1.pyw

-a—- 24.06.2019 22:43 128 script1b.py

-a—- 04.07.2019 18:51 56 showargs.py

-a—- 28.06.2019 00:29 162 threenames.py

-a—- 24.06.2019 21:16 120 tst1.py

-a—- 24.06.2019 22:49 126 what.py

-a—- 24.06.2019 23:56 136 what2.py

… and then we can start the python-script ‘script1.py’:

PS C:\Users\gerd_2\code> python script1.py

win32

1267650600228229401496703205376

pythonpythonpythonpythonpythonpythonpythonpython

PS C:\Users\gerd_2\code>

But because we will here use the IDLE tool we proceed differently. We open the File-Menue to get the desired file script1.py:

Open file-directory for file search

Then we load  the python-script script1.py in the editor of the IDLE tool:

The text of the script

and then activate the RUN button for execution:

Activate the RUN button to execute the script

The script will then be executed and you will see the effect of the execution in the python shell. This looks the same as when you would have called the script within the power-shell calling  the python-shell.

There is still the other option to get the module running by the import command:

>>> import script1.py

win32

1267650600228229401496703205376

pythonpythonpythonpythonpythonpythonpythonpython

Traceback (most recent call last):

File “<pyshell#7>”, line 1, in <module>

import script1.py

ModuleNotFoundError: No module named ‘script1.py’; ‘script1’ is not a package

>>>

The import call works, but at the same time the python-shell states some error, that ‘script1.py’ is not recognized as a true module. This has to be clarified in the next session.

 

 

 

AAI THEORY V2 – DEFINING THE CONTEXT

eJournal: uffmm.org,
ISSN 2567-6458, 24.Januar 2019
Email: info@uffmm.org
Author: Gerd Doeben-Henisch
Email: gerd@doeben-henisch.de

CONTEXT

An overview to the enhanced AAI theory  version 2 you can find here.  In this post we talk about the second chapter where you have to define the context of the problem, which should be analyzed.

DEFINING THE CONTEXT OF PROBLEM P

  1. A defined problem P identifies at least one property associated with  a configuration which has a lower level x than a value y inferred by an accepted standard E.
  2. The property P is always part of some environment ENV which interacts with the problem P.
  3. To approach an improved configuration S measured by  some standard E starting with a  problem P one  needs a process characterized by a set of necessary states Q which are connected by necessary changes X.
  4. Such a process can be described by an actor story AS.
  5. All properties which belong to the whole actor story and therefore have to be satisfied by every state q of the actor story  are called  non-functional process requirements (NFPRs). If required properties are are associate with only one state but for the whole state, then these requirements are called non-functional state requirements (NFSRs).
  6. An actor story can include many different sequences, where every sequence is called a path PTH.  A finite set of paths can represent a task T which has to be fulfilled. Within the environment of the defined problem P it mus be possible to identify at least one task T to be realized from some start state to some goal state. The realization of a task T is assumed to be ‘driven’ by input-output-systems which are called actors A.
  7. Additionally it mus be possible to identify at least one executing actor A_exec doing a  task and at least one actor assisting A_ass the executing actor to fulfill the task.
  8. A state q represents all needed actors as part of the associated environment ENV. Therefore a  state q can be analyzed as a network of elements interacting with each other. But this is only one possible structure for an analysis besides others.
  9. For the   analysis of a possible solution one can distinguish at least two overall strategies:
    1. Top-down: There exists a group of experts EXPs which will analyze a possible solution, will test these, and then will propose these as a solution for others.
    2. Bottom-up: There exists a group of experts EXPs too but additionally there exists a group of customers CTMs which will be guided by the experts to use their own experience to find a possible solution.

EXAMPLE

The mayor of a city has identified as a  problem the relationship between the actual population number POP,    the amount of actual available  living space LSP0, and the  amount of recommended living space LSPr by some standard E.  The population of his city is steadily interacting with populations in the environment: citizens are moving into the environment MIGR- and citizens from the environment are arriving MIGR+. The population,  the city as well as the environment can be characterized by a set of parameters <P1, …, Pn> called a configuration which represents a certain state q at a certain point of time t. To convert the actual configuration called a start state q0 to a new configuration S called a goal state q+ with better values requires the application of a defined set of changes Xs which change the start state q0 stepwise into a sequence of states qi which finally will end up in the desired goal state q+. A description of all these states necessary for the conversion of the start state q0 into the goal state q+ is called here an actor story AS. Because a democratic elected  mayor of the city wants to be ‘liked’ by his citizens he will require that this conversion process should end up in a goal state which is ‘not harmful’ for his citizens, which should support a ‘secure’ and ‘safety’ environment, ‘good transportation’ and things like that. This illustrates non-functional state requirements (NFSRs). Because the mayor wants also not to much trouble during the conversion process he will also require some limits for the whole conversion process, this is for the whole actor story. This illustrates non-functional process requirements (NFPRs). To realize the intended conversion process the mayor needs several executing actors which are doing the job and several other assistive actors helping the executing actors. To be able to use the available time and resources ‘effectively’ the executing actors need defined tasks which have to be realized to come from one state to the next. Often there are more than one sequences of states possible either alternatively or in parallel. A certain state at a certain point of time t can be viewed as a network where all participating actors are in many ways connected with each other, interacting in several ways and thereby influencing each other. This realizes different kinds of communications with different kinds of contents and allows the exchange of material and can imply the change of the environment. Until today the mayors of cities use as their preferred strategy to realize conversion processes selected small teams of experts doing their job in a top-down manner leaving the citizens more or less untouched, at least without a serious participation in the whole process. From now on it is possible and desirable to twist the strategy from top-down to bottom up. This implies that the selected experts enable a broad communication with potentially all citizens which are touched by a conversion and including  the knowledge, experience, skills, visions etc. of these citizens  by applying new methods possible in the new digital age.