Python help, how to set a value above definitions

Scripting
1

Hi guys, a noob Python question here.
My scripts are becoming more complex and need better control. I have a few definitions in the script and need to have some variables that are accessible above them so I don’t have to return the value via the definition. What is the best approach?

I have used sticky as a simple workaround, but I am sure there are better options.

Super simple example:

import rhinoscriptsyntax as rs

string = "Nothing"

def setString():
    string = "Something"

def getString():
    print string

setString()
getString()

returns “Nothing”

2

The issue here is that you’ve defined string as a global variable in the outer most scope, but in the setString() function you re-define a new string variable within the function scope that gets destroyed once the function call ends.

This does the trick:

VALUE = None  # global variables are capitalized

def set_value(new_value):
    global VALUE
    VALUE = new_value

if __name__ == "__main__":
    set_value("something")
    print VALUE

Getter and setter functions are superfluous here, because you can always just call and set VALUE from anywhere in the script, since it’s a global variable.

And please do the community a favor and use Pythonic notation! No camel case for function names!! :slight_smile:

3

… for a better understanding / background - check out some sources for “phyton variable scope”.
One of google first hits:

your initial problem / question is described in paragraph
Scenario 1: Global Scope

and @diff-arch s solution with the global keyword - you ll find below.
Global Keyword

also check / google “resolve naming conflicts” (which variable is addressed if keywords missing, but same name)

4

global works fine! Thanks! That’ll make my life easier!

import rhinoscriptsyntax as rs

STRING = "Nothing"

def setString():
    global STRING 
    STRING = "Something"

def getString():
    print STRING 

setString()
getString()

I’ll google that for sure! As I have no idea about what you just wrote :wink:

Thanks!
It helps when you know what terminology to search for :wink:

Thanks a lot guys!

5

PS! I don’t use if name == “main”: since I put them on buttons with -RunPythonScript () and that doesn’t like if__name__…
Any ways to work around that too?

6

print(__name__)

and

if __name__ == '__main__': pass

both work for me. Have you just forgotten the dunders?

7

if __name__ == "__main__" checks whether you are currently executing that Python file, meaning the one containing the if statement and only then runs the code within that statement.
This is handy, because it isn’t run when you import from the same file, instead of running it itself.

1 Like
8

I am not sure what a dunder is, but if I put this in a button and click the button then I get nothing:

! _-RunPythonScript (

import rhinoscriptsyntax as rs
if __name__ == "__main__":
    crv_id = rs.GetObject("Select curve",rs.filter.curve,preselect=True)
    print rs.CurveLength(crv_id)

)
9

Now now… :wink:

10

Got it, just understood what “camel” referred to :slight_smile:

But googling this didn’t return anything useful. What do you consider the correct way?
If I like it I’ll adopt it!

11

Dunder == Double underscore

Oh cool, I didn’t realise you could run Python from inside a button, I’ve not tried that before.

Add in a simple print(__name__) you’ll see in a Button you want to test for __builtin__:

! _-RunPythonScript (

import rhinoscriptsyntax as rs
print(__name__)
if __name__ == "__builtin__":
    crv_id = rs.GetObject("Select curve",rs.filter.curve,preselect=True)
    print rs.CurveLength(crv_id)

)

You don’t need it anyway though, as I don’t think you can import the code in a Button anymore than you can that from a GhPython component. Neither are easily usable as modules.

However, adding in a name == main guard clause into an external module, that you import into your button could be a great idea though, e.g. for testing. But you probably need to add its path to sys.path to import it.

1 Like
12

This is a pretty good reference:

The style of the Pythonic notation is defined by PEP8:
https://pep8.org/

1 Like