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Update 'non-ros-files/Programming_Rules.md'

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winterhalderp 2021-04-20 11:57:14 +02:00
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non-ros-files/Programming_Rules.md
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@ -29,10 +29,17 @@ The next chapters will describe the content of the files inside a package direct
## setup.py
The file `<colcon_ws>/<package_dir>/setup.py` defines how you can call your scripts using a self defined in the command line. This results in commands such as
`ros2 run pubsub talker`
`ros2 run pubsub listener`.
This is done by linking the correct Python scripts to the names _talker_ and _listener_ using the file _setup.py_, eg.
The file setup.py is used to create entry points, meaning you link your python scripts to names which you can be called through `ros2 run ...`. In order for this to work your python scripts must be written using the following mechanism
```python
def main():
# main code
if __name__ == "__main__":
main()
```
in which you put all of your code inside `main()`. This prevents any code from being run, if this script is not run as main.
Linking your scripts to names is done inside the file _setup.py_ by defining entry points:
```python
entry_points={
'console_scripts': [
@ -41,4 +48,6 @@ entry_points={
],
},
```
From this you can see that you need to follow the Python programming style of creating a _main_ procedure, in order for the entry points to work.
The _setup.py_-excerp above links the the function `main()` from the scripts _talker.py_ and _listener.py_ from inside `/pubsub` to the names _talker_ and _listener_. This way they can be called using `ros2 run pubsub talker` or `ros2 run pubsub listener`.
From this you can see that you need to follow the Python programming style of creating a _main()_ procedure, in order for the entry points to work.