The same thing as a script in idle

# indicates an comment

In addition to the if statement above we have elif and else

Again you can see that the block starts with “:” and is indented.

Calling functions from a Module

This is how we call a function (method) from a module.

... and this is the result:

Executing Modules

Often modules contain only function or class (see later) definitions

However it is also possible to include the function calls (the main routine)

into the module e.g. to demonstrate how the functions are to be used.

In this case the name of the module changes to __main__

We can therefore find out if the module is imported or executed by checking the name variable:

if __name__ == "__main__"

this executes the main code only if not imported into a main program

Command Line Arguments

Programs can be called with arguments. When calling an editor you my give

the name of the file to be edited as an argument.

There may also be options that are passed as arguments, e.g.

ls -ls $HOME

These arguments can be read (as strings) in Python:

You may then convert an argument from string to int with

maxFib=int(argv[1])

Running the module with args

This code checks if we are running in idle, in which case it asks the user for the arguments.

In case we are called from the command line the arguments are already passed into sys.argv

Files

In order to read of write a file it must first be opened:

f = open(‘filename’,’w’)

After which you can write the file. In read mode, the ‘w’ must be replaced by ‘r’

Classes

In object oriented programming languages you can define classes

encapsulating data and functions (methods in the oo jargon) that act on these data.

You can create sub-classes having most of the properties of the

base class but provide more data and/or methods or some of the methods are modified (overridden).

This is called inheritance.

Python implements these features.

While in many object oriented languages we distinguish between public and private data,

in Python all data are public.

A convention is to precede a variable name with an ‘_’ if it is not intended for use external to the class.

---+++

Creating Classes

The syntax for creation of classes is similar to functions





i is an instance variable

f is a method

You may define a method with name __init__which is called when

the instance object of the class is created (in the above example: mc = MyClass ()

The short description of the class can be found in the instance variable _ _doc__

Classes and the Sensors

As classes describe real world objects they are particularly using for describing our sensors

Connection details, calibration parameters etc. can be described in the instance variables

Actions of the sensors like triggering, readout etc. are implemented in methods.

Instance initialization

There is a special method named _ _init__ which is called when the instance of a class is created.

This method allows to

• Initialize instance variables
• Initialize e.g. registers, addresses and the like
• Setup I/O for sensors

A Class Implementation realizing a simple Calculator

A Sensor Demo

The cobbler PinOut

The Sensors

This is the idea:

The hardware includes:

• a color sensor
• an ultra-sonic distance sensor
• an rgb LED (not strictly necessary)

When a colored paper sheet is placed in front of the senors then this sheet

with the right color will be seen in the virtual world.

The distance of the sheet to the sensors is also reflected in the virtual world.

The sensors in the virtual world

We see the distance sensor in front and the color sensor

with its LEDs switched off, in the back

The (white) paper sheet is in frontof the distance sensor

The red ball is the center of the coordinate system