STARTING WITH PYTHON3 – The very beginning – part 6

Journal: uffmm.org,
ISSN 2567-6458, July 20-22, 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 overall context is still the python Co-Learning project.

SUBJECT

Meanwhile I am beginning to combine elements of the python language with some applied ideas (in the last section the idea of cognitive entropy illustrated with the equalization of strings). In this section I address the idea of a simple 2-dimensional virtual world, how to represent it with python. In later sections I will use this virtual worlds for some ideas of internal representations and some kinds of learning in an artificial actor.

Remark: for general help information go directly to the python manuals, which you can find associated with the entry for python 3.7.3 if you press the Windows-Button, look to the list of Apps (= programs), and identify the entry for python 3.7.3. If you open the python entry by clicking you see the sub-entry python 3.7.3 Manuals. If you click on this sub-entry the python documentation will open. In this documentation you can find nearly everything you will need. For Beginners you even find a small tutorial. … Yes, and there is all this and more in the world wide web too.

SZENARIO

Motivation

Because we want to introduce step-wise artificial actors which can learn, show some intelligence, and can work in teams, we need a minimal virtual world to start (this virtual world is a placeholder for the real world later if applied to the real world (RW) by sensors and actors). Although there is a big difference between the real world and a virtual world a virtual world is nevertheless very helpful for introducing basic concepts. And, indeed, finally if you are applying to real world data you will not be able to do this without mathematical models which represent virtual structures. You will need lots of mappings between real and virtual and vice versa. Thus from a theoretical point of view any kind of virtual model will do, the question is only how ‘easily’ and how ‘good’ it fits.

Assumptions Virtual World (VW)

  1. A 2-dimensional world as a grid together with a world clock CLCK. The clock produces periodic events which can be used to organize a timely order.

  2. There is an x and y axis with the root (0,0) in the upper left corner

  3. A coordinate (x,y) represents a position.

  4. A position can be occupied by (i) nothing or (ii) by an object. Objects can be obstacles, energy objects (= Food), by a virtual executive actor, or even more.

  5. Only one object per position is allowed.

  6. It is assumed that there are four directions (headings): ‘North (N)’ as -Y, ‘East (E)’ as +X, ‘South (S)’ as +Y, and ‘West (W)’ as -X.

  7. Possible movements are always only in one of the main directions from one cell to the adjacent cell. Movements will be blocked by obstacle objects or actor objects.

  8. A sequence of movements realizes in the grid a path from one position to the next.

  9. The size of the assumed grids is always finite. In a strict finite world the border of the grid blocks a movement. In a finite-infinite world the borders of the grid are connected in a way that the positions in the south lead to the position in the north and the positions in the east lead to the positions in the west, and vice versa. Therefor can a path in an finite-infinite world become infinite.

  10. A grid G with its objects O will be configured at the beginning of an experiment. Without the artificial actors all objects are in a static world assumed to be permanent. In a dynamic world there can be a world function f_w inducing changes depending from the world clock.

  11. During an experiment possible changes in the world can happen through a world function f_w, if such a function has been defined. The other possible source for changes are artificial actors, which can act and which can ‘die’.

Remark: The basic idea of this kind of a virtual world I have got from a paper from S.W.Wilson from 1994 entitled ZCS: a zeroth level classifier system published in the Journal Evolutionary Computation vol. 2 number 1 pages 1-18. I have used this concept the first time in a lecture in 2012 (URL: https://www.doeben-henisch.de/fh/gbblt/node95.html). Although this concept looks at a first glance very simple, perhaps too simple, it is very powerful and allows very far reaching experiments (perhaps I can show some aspects from this in upcoming posts :-)).

ACTOR STORY
  1. There is a human executive actor as a user who uses a program as an assisting actor by an interface with inputs and outputs.

  2. The program tries to construct a 2D-virtual world in the format of a grid. The program needs the size of the grid as (m,n) = (number of columns, number of rows), which is here assumed by default as equal m=n. After the input the program will show the grid on screen.

  3. Then the program will ask for the percentage of obstacles ‘O’ and energy objects (= food) ‘F’ in the world. Randomly the grid will be filled according to these values.

  4. Then a finite number of virtual actors will be randomly inserted too. In the first version only one.

POSSIBLE EXTENSIONS

In upcoming versions the following options should be added:

  1. Allow multiple objects with free selectable strings for encoding.

  2. Allow multiple actors.

  3. Allow storage of a world specification with reloading in the beginning instead of editing.

  4. Transfer the whole world specification into an object specification. This allows the usage of different worlds in one program.

IMPLEMENTATION

vw1b.py

And with separation of support functions in an import module:

vw1c.py

gridHelper.py(The import module)

EXERCISES

m=int(input(‘Number of columns (= equal to rows!) of 2D-grid ?’))

The input() command generates as output a string object. If one wants to use as output numbers for follow-up computations one has to convert the string object into an integer object, which can be done with the int() operator.

mx=nmlist(n)

Is the call of the nmlist() function which has been defined before the main source code (see. above)(in another version all these supporting functions will again be stored as an extra import module:

printMX(mx,n)

This self-defined function assumes the existence of a matrix object mx with n=m many columns and rows. One row in the matrix can be addressed with the first index of mx like mx[i]. The ‘i’ gives the number of the row from ‘above’ starting with zero. Thus if the matrix has n-many rows then we have [0,…,n-1] as index numbers. The rows correspond to the y-axis.

mx = [[‘_’ for y in range(n)] for x in range(n)]

This expression is an example of a general programming pattern in python called list comprehension (see for example chapters 14 and 22 of the mentioned book of Mark Lutz in part 1 of this series). List comprehension has the basic idea to apply an arbitrary python expression onto an iteration like y in range(n). In the case of a numeric value n=5 the series goes from 0 to 4. Thus y takes the values from 0 to 4. In the above case we have two iterations, one for y (representing the rows) and one vor x (representing the columns). Thus this construct generates (y,x) pairs of numbers which represent virtual positions and each position is associated with a string value ‘_’. And because these instructions are enclosed in []-brackets will the result be a set of lists embedded in a list. And as you can see, it works 🙂 But I must confess that from the general idea of list comprehension to this special application is no direct way. I got this idea from the stack overflow web site (https://stackoverflow.com/questions) which offers lots of discussions around this topic.

for i in range(no):

x=rnd.randrange(n)

y=rnd.randrange(n)

mx[x][y]=obj

A simple for-loop to generate random pairs of (x,y) coordinates to place the different objects into the 2D-grid realized as a matrix object mx.

Demo

PS C:\Users\gdh\code> python vw1.py

Number of columns (= equal to rows!) of 2D-grid ?5

[‘_’, ‘_’, ‘_’, ‘_’, ‘_’]

[‘_’, ‘_’, ‘_’, ‘_’, ‘_’]

[‘_’, ‘_’, ‘_’, ‘_’, ‘_’]

[‘_’, ‘_’, ‘_’, ‘_’, ‘_’]

[‘_’, ‘_’, ‘_’, ‘_’, ‘_’]

Percentage (as integer) of obstacles in the 2D-grid?45

Number of objects :

11

Position :

3 2

Position :

2 3

Position :

3 2

Position :

3 2

Position :

0 1

Position :

2 2

Position :

0 1

Position :

4 3

Position :

0 2

Position :

3 1

Position :

1 4

New Matrix :

[‘_’, ‘O’, ‘O’, ‘_’, ‘_’]

[‘_’, ‘_’, ‘_’, ‘_’, ‘O’]

[‘_’, ‘_’, ‘O’, ‘O’, ‘_’]

[‘_’, ‘O’, ‘O’, ‘_’, ‘_’]

[‘_’, ‘_’, ‘_’, ‘O’, ‘_’]

Percentage (as integer) of Energy Objects (= Food) in the 2D-grid ?15

Number of objects :

3

Position :

3 4

Position :

0 4

Position :

4 1

New Matrix :

[‘_’, ‘O’, ‘O’, ‘_’, ‘F’]

[‘_’, ‘_’, ‘_’, ‘_’, ‘O’]

[‘_’, ‘_’, ‘O’, ‘O’, ‘_’]

[‘_’, ‘O’, ‘O’, ‘_’, ‘F’]

[‘_’, ‘F’, ‘_’, ‘O’, ‘_’]

Default random placement of one virtual actor

Position :

2 2

New Matrix :

[‘_’, ‘O’, ‘O’, ‘_’, ‘F’]

[‘_’, ‘_’, ‘_’, ‘_’, ‘O’]

[‘_’, ‘_’, ‘A’, ‘O’, ‘_’]

[‘_’, ‘O’, ‘O’, ‘_’, ‘F’]

[‘_’, ‘F’, ‘_’, ‘O’, ‘_’]

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.

 

 

 

STARTING WITH PYTHON3 – The very beginning – V2

Journal: uffmm.org,
ISSN 2567-6458, July 5, 2019
Email: info@uffmm.org
Author: Gerd Doeben-Henisch
Email: gerd@doeben-henisch.de

CONTEXT

This is an update of the post ‘STARTING WITH PYTHON3 – The very beginning‘ from July-1, 2019. The original version was not ‘wrong’, but it seems, after a few days later, one can and should improve it. The main motivation for this new version is my experience as a linux programmer working with windows 10: learning by doing I detected a litle more radical approach to begin python programming with win10. This post is part of the overall  topic ‘Co-Learning with python 3‘.

OVERVIEW

In this updated version I will introduce some bits of the win10 environment which you will need for your python programming. Then I demonstrate the very first steps with some lines of code. Very important for all your own activities: in the beginning get you a helpful book to guide your start. After trying many sources I have actually the following recommendations:

  • Mark Lutz, Learn Python, 2013,5th ed.,Sebastopol (CA), O’Reilly
  • To get the sources: https://www.python.org/
  • Documentation: https://docs.python.org/3/
  • Python Software Foundation (PSF): https://www.python.org/psf-landing/
  • Python Community: https://www.python.org/community/

THE WIN10-ENVIRONMENT

When you start programming  you need a direct knowledge about your computing environment, in that case the win10 operating system. While linux is built up with an open mind and tries to make everything transparent, win10 is somehow the opposite: it is a closed box, and to work with it in direct contact with the operating system is not very well supported. Thus to work as a programmer with win10 is not what you ideally want. But now we are there and have to get the programming done.

After my first expriments with win10 I detected the following tools as very helpful to start programming: (i) The editor for the system and environment variables and (ii) the powershell. These tools allow you to define the operating system environment for your python programming  in a minimal way.

The editing of the system and environment variables you can reach by the following key-operations:

Editing System and Environment Variables

  1. Hit the windows key together with the key for ‘R’
  2. This opens a small window with a textfield-entry.
  3. In this field you enter the string ‘control’
  4. This opens a page with different topics for to manipulate some aspects of your system (because my computer is in the German-Mode I have the heading ‘Einstellungen des Computers ändern’, something like ‘Change options of the computer’).
  5. Here you select the topic ‘System and Security’
  6. Then another page opens with several topics, one is ‘System’, which you should select.
  7. On this new page you can see at the left border some more topics. The last one mentions something like ‘Extended System Options’. Select this
  8. Before you see the next page you will be asked to enter the Super-User Password. Thus you must be super-user to do this.  To be a real programmer you must have this rights to get a full understanding of what is going on.
  9. Then  the editor for system and environment variables pops up:
Editor for system and enviroment variables

 

  1. The interesting button is in the right down corner, in German: Umgebungsvariablen (‘environment variables’)
  2. Click this button and you will finally see the editor you are looking for:
Finally the editor to edit private and environment variables
  1. For the upcoming actions we need only the path-variable. One can highlight the Path-entry and select it with ‘Editing’ (German: ‘Bearbeiten’):
The window showing all the entries of the path-variable.
  1. Now you can see all the entries of the path variable nicely ordered one after the  other. This is a special service because the path-variable as such (as you will see later when using the power-shell) is one string. Here this string is splitted up into the different sub-strings. This allow you to add some new string or — also very important — to delete a substring. As You can see in the figure there is as last line an entry including the name Python . This line is the whole directory path on the drive C:\ where my actual python version is stored.

CLEAN UP BEFORE

Now, if You know where and how you can edit the basic system variables it can be a good idea to clean up the whole system with regard to older python installations. In my case I had tried  before — as a complete newbie — several python distributions like WinPython and Anaconda in different versions at different locations in the system, this accompanied with different installations of the python language. You can imagine that this caused finally some confusion what is where and what is causing which  effect.

Thus I decided to start from scratch, removing all the old stuff to get a ‘point zero’ for beginning.

The first step was to use the win10 explorer program with the find option in the small text-field up right.

Part of the win10-explorer window showing a find-operation on the whole PC

After you have entered your search-string, in this case ‘python’, you have to say (left up corner) the region, in which you want the search to happen. I have selected the whole PC.

After some while you see all locations as a complete path where the search-string python could be found. When I started my clean-up action there where lots of locations with different python installations, now there is only one left, which I am actually using.

But caution: If you want to delete the old installations you have (i) to look to the uninstall options/ programs to activate these to remove all stuff; (ii) finally you have to enter the editor for system and environment variables (see above) to delete all entries there, which are now obsolet.

GET YOUR PYTHON

Now, if you have set everything with Python to zero get your python version from the python home page: https://www.python.org/.

This page is a bit confusing. Stay cool. You can detect a field with the header Downloads and a hint to the latest version. In this case it shows 3.7.3. Click this.

Python Home Page for Downloads

The next page is completely confusing. The interesting part of this page is somewhere in the middle listing the different download files:

List of download files

We are interested in the 32-Bit version although I am working on a 64-Bit machine. For the learning the 32-Bit version is more flexibel and completely sufficient.

If you click the windows installer for python (second line from below) then a download notice will be shown asking for confirmation:

Confirm download of python installer

Select ‘datei speichern’ (download file) and the installer will be  loaded in your download directory.

In the list of files you can also see   a colum with the MD5-Checksum. This is an offer to check whether the file you have downloaded is indeed not corrupted in some way (viruses etc.) To use the MD5-Checksum code You need a MD5-software tool. I found a good description at this site: https://www.it-administrator.de/downloads/software/197801/, which points you to the following product page: https://www.novirusthanks.org/products/md5-checksum-tool/.

This looks quite OK. But if you want to apply it you have to surround some difficulties when you try to search for your file to check with the directory browser. In my case it shows the directory of the super-user first. To get my python download file I have to select the main drive C:\, there I have to select from Users my actual role as user gdh, and then I can find my download folder with the python exe file to be checked. From the web site with the files list I have copied the MD5-Checksum:

MD5-checksum tool at work

Luckily the check looks good. This encourages to install python 3.7.3 by clicking on the python installer.

Python Installer Window

Because I have already installe python I can only modify it or repair or uninstall. If you click it the first time you will be able to select the option Install. In that case it will propose a directory and it will install python. Before You say Yes You can also click the flag ‘Set Path Variable‘. I did this but the interesting point is that it had no effect when using the power shell (see below). Only when I added the path again with the aid of the powershell it took effect.

USING THE POWERSHELL

To get the powershell you have to press the windows button, then a list of Apps (programs) appears. Under the letter ‘W’ you see the windows powershell. Clicking this topic you will detect several versions of the power shell: 64-Bit and 32-Bit (indicated by (x86)), and the old standard version as well as a more enhanced version called integrated script environment (ISE).

I have started with the old, simple standard version. By right-clicking with your mouse you can add the option to attach the powershell to the task bar which makes it easy to call it up again later.

Section of my task bar including icons for normal powershell (left) and integrated script environment (right)

If you click on the powershell icon the powershell window will open:

Powershell window with the command python entered

If you would confirm this command by pressing the enter key — and you would not have set the path variable with the path of the python executing modul python.exe before — then there would appear a message that the command ‘python’ is not known (I cannot demonstrate it here because I have set the path variable on account of this message meanwhile).

There exists a workaround without setting the path variable explicitly by give the whole path of the python modul, like this:

Powershell calling python with explicit path

You see, this works fine. To make life easier I have set the environment path variable with this python execution path. Then you can enter the command python alone and a python environement opens up.

But, wait a moment. Setting the path variable with the editor for the environment variable alone (see above) this has no effect for the powershell! Also the powershell can show the content of the path-variable correctly:

Powershell showing content of path-variable

(This is the version of the path variable after I have added the path with the powershell too!)

To add the path variable for the python modul explicitly in the powershell you can enter the following  command:

PS C:\Users\gdh> $Env:PATH +=”;C:\Users\gdh\AppData\Local\Programs\Python\Python37-32″

When I did this everything worked fine. Don’t ask, why it didn’t work before with the editing of the environment variable PATH alone.  This is at a first glance like ‘Software mystik’. With much more time for research there exists perhaps an explanation. My first guess would be, that the communication between the powershell and the environment variable has some hidden factors. For more very detailed explanations about the powershell and the editing of the environment variable you can find a good document from microsoft here: https://docs.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_environment_variables?view=powershell-6.

PROGRAMMING PYTHON

For first programming steps look to the first version of this post beginning at the header FIRST PROGRAMMING STEPS somewhere in the middle of the page.

More coding will follow soon.

STARTING WITH PYTHON 3 – The very beginning

eJournal: uffmm.org,
ISSN 2567-6458, July 1, 2019
Email: info@uffmm.org
Author: Gerd Doeben-Henisch
Email: gerd@doeben-henisch.de

CONTEXT

The idea is to give some advice to start with python 3 programming. In other posts I have used an integrated package using WinPython including the integrated  development package  spyder. While such an integrated package offers lots of nice tools it hides the basic structures of your system and of the language. Therefore I decided to start again at a more basic level using only the python language and the windows command shell (I myself are working with an ubuntu system for the normal python programming and for the work with a python web-framework called ‘django’). Because I myself am not too much experienced with the windows 10 environment it challenges me to investigate the win10 environment to some degree.

GETTING STARTED FROM SCRATCH: DOWNLOAD PYTHON

To get a fresh start from scratch I have removed all python stuff from my machine.  Then I have downloadad the newest pythion version for windows from https://www.python.org/. This is python version 3.7.3 in the 32-Bit version. There exists also a 64-Bit version, but because not all the different modules are already prepared for the 64-Bit version the 32-Bit version is more flexible. To learn python this is more than enough. To switch to a 64-Bit version would be simple.

LOCAL WINDOWS ENVIRONMENT

On my machine the installation path is:

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

To test whether python works on your windows machine you can activate the WindowsPowerShell. You will find this shell by klicking on the Windows Icon in the left corner of your laptown whic opens the list of all Windows-Apps (programs).  At the end of this list there are some windows-Apps including the Windows-Power-Shell. I took the first one. By clicking on the right mouse-button I selected to attach the power-shell on the task bar. This allows me to click once on the icon of the power shell and the power shell will open.

Typing the command ‘python’ the first time into the command line will cause an error message, because Windows does not know where to find the command ‘python’. You can do two things: (i) enter the whole path for python or (ii) inform the PATH-variable about the python path.

Enter the whole path worked out:

PS C:\Users\gerd_2> C:\Users\gerd_2\AppData\Local\Programs\Python\Python37-32\python

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.

>>

Because this procedure is a bit cumbersom I tried the other proposal, to edit the PATH-variable. One proposal (from the community) goes like this:

  1. Open the Start Search, type in “env”, and choose “Edit the system environment variables”:
  2. Click the “Environment Variables…” button.
  3. Under the “System Variables” section (the lower half), find the row with “Path” in the first column, and click edit.
  4. The “Edit environment variable” UI will appear.

I could edit the PATH-variable this way, but ist showed no effect. Therefore I tried another procedure, where one can modify the PATH-variable directly from the power-shell. The needed command has the following format:

$Env:PATH += “;Wanted Path”

This addresses the PATH variable, let the actual content as it is and adds after a semicolon the needed path. With the command

$Env:PATH

you can check the actual values of the variable PATH and after adding your new path

PS C:\Users\gerd_2> $Env:PATH +=”;C:\Users\gerd_2\AppData\Local\Programs\Python\Python37-32″

youcan check again. It worked, I got my new path added to  the variable. But, even more important, now it worked. Enterin in the power shell only ‘python’ it worked:

PS C:\Users\gerd_2> python
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.
>>>

I also tried the ‘help-option’ like this:

>>> help()

Welcome to Python 3.7’s help utility!

If this is your first time using Python, you should definitely check out

the tutorial on the Internet at https://docs.python.org/3.7/tutorial/.

Enter the name of any module, keyword, or topic to get help on writing

Python programs and using Python modules. To quit this help utility and

return to the interpreter, just type “quit”.

To get a list of available modules, keywords, symbols, or topics, type

“modules”, “keywords”, “symbols”, or “topics”. Each module also comes

with a one-line summary of what it does; to list the modules whose name

or summary contain a given string such as “spam”, type “modules spam”.

I tried e.g.  the ‘modules option:

help> modules

Please wait a moment while I gather a list of all available modules…

__future__ _tracemalloc glob secrets

_abc _warnings gzip select

_ast _weakref hashlib selectors

_asyncio _weakrefset heapq setuptools

From this I selected the  ‘socket’-option:

help> socket

Help on module socket:

NAME

socket

DESCRIPTION

This module provides socket operations and some related functions.

On Unix, it supports IP (Internet Protocol) and Unix domain sockets.

On other systems, it only supports IP. Functions specific for a

socket are available as methods of the socket object.

Functions:

socket() — create a new socket object

socketpair() — create a pair of new socket objects [*]

fromfd() — create a socket object from an open file descriptor [*]

fromshare() — create a socket object from data received from socket.share() [*]

Thus this function works and looks promising.

FIRST PROGRAMMING STEPS

The main idea of using python is to be able to write some program code which then the machine can run. The basic processing steps are

  1. Start python in the power shell by typing  ‘python’
  2. Enter some python code you want to test.
  3. If you want to edit many python commands together then take a text editor and write some text which looks like python code.
  4. The text you enter directly into a python command line or a edited text in a file which you can load both will be handed out to the python interpreter which translate these pyton commands into a byte code which in turn will be run by the python virtual machine (PVM).

It is helpful befor you start programming to generate at least one folder where you will store your python programs. Following the proposal from Mark Lutz (see below references) I generate in my main directory a folder called ‘code’:

PS C:\> cd $HOME

PS C:\Users\gerd_2> mkdir code

Verzeichnis: C:\Users\gerd_2

Mode LastWriteTime Length Name

—- ————- —— —-

d—– 01.07.2019 18:40 code

To edit a first simple program with name ‘script1.py’ I have called the notepad editor in the power shell like this:

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

In the editor I have typed the following simple text:

# FILE: script1.py

import sys

print(sys.platform)

print(2**100)

x=’python’

print(x*8)

Then I have stored this file in the ‘code’ folder. Wih the command ‘dir’ one can have a look into the ‘code’ folder:

PS C:\Users\gerd_2\code> dir

Verzeichnis: C:\Users\gerd_2\code

Mode LastWriteTime Length Name

—- ————- —— —-

-a—- 01.07.2019 18:41 92 script1.py

To check what happens when I load this script with the python interpreter one can enter the following command:

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

win32

1267650600228229401496703205376

pythonpythonpythonpythonpythonpythonpythonpython

STREAM REDIRECTION

One can also redirect the output of the python interpreter from the console into a file:

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

Then one can again call an editor like notepad to read the content of this file:

PS C:\Users\gerd_2\code> notepad savesrc.txt

CONTENT savesrc.txt:

win32

1267650600228229401496703205376

pythonpythonpythonpythonpythonpythonpythonpython

MODULES

Like many other programming language python organizes larger programs by putting together  smaller programs like building blocks. These blocks are called modules and this strategy  can only work if one follows some rules. Mark Lutz formulates it as follows:

“… a module is mostly just a package of variable names, known as a namespace, and the names within that package are called attributes. An attribute is simply a variable name that is attached to a specific object (like a module).” (Lutz, Mark. Learning Python (S.70). O’Reilly Media. Kindle-Version)

One possibility to fetch a module is to use the import command, either directly in a python console or indirectly as command in a python program text. Thus with going direct to the console:

PS C:\Users\gerd_2\code> python
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\\code’

Here the module ‘os’ has been imported and within tis module exists a function ‘getcwd()’ which fetches the actual path you are in. In my case my home directory and there the folder ‘code’. Doing an import with the new file ‘script1.py’ it works like this:

PS C:\Users\gerd_2\code> python

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 script1

win32

1267650600228229401496703205376

pythonpythonpythonpythonpythonpythonpythonpython

Thus the import also causes a run of the script.

If one wants to know which kinds of names are used in the module one can use the command dir():

>>> dir(script1)

[‘__builtins__’, ‘__cached__’, ‘__doc__’, ‘__file__’, ‘__loader__’, ‘__name__’, ‘__package__’, ‘__spec__’, ‘sys’, ‘x’]

TO BE CONTINUED…

Go back to the main page.

SOME HELPFUL REFERENCES

  • Mark Lutz, Learn Python, 2013,5th ed.,Sebastopol (CA), O’Reilly
  • To get the sources: https://www.python.org/
  • Documentation: https://docs.python.org/3/
  • Python Software Foundation (PSF): https://www.python.org/psf-landing/
  • Python Community: https://www.python.org/community/