pyqgis - Get value of Variable in custom python expression function

I am writing a custom python expression function to return the value of a variable. By variable, I mean the layer, project, or global variables. I looked at this answer https://gis.stackexchange.com/a/189815/94852 and came up with the following code.

from qgis.core import *
from qgis.gui import *
from qgis.utils import *

@qgsfunction(args='auto', group='Custom')
def env(var_name, feature, parent):
    """ Returns the value of the variable 'var_name' 
    Example usage: env('user_full_name') """


    active_layer = iface.activeLayer()

    if QgsExpressionContextScope.hasVariable(QgsExpressionContextUtils.layerScope(active_layer), var_name):
        return QgsExpressionContextScope.variable(QgsExpressionContextUtils.layerScope(active_layer), var_name)

    elif QgsExpressionContextScope.hasVariable(QgsExpressionContextUtils.projectScope(), var_name):
        return QgsExpressionContextScope.variable(QgsExpressionContextUtils.projectScope(), var_name)

    elif QgsExpressionContextScope.hasVariable(QgsExpressionContextUtils.globalScope(), var_name):
        return QgsExpressionContextScope.variable(QgsExpressionContextUtils.globalScope(), var_name)


    else:
        return ""

I am wondering if there is a better way to do it with fewer lines of code, and if there exists a simpler function getProjectVariable() similar to setProjectVariable(), since I have not been able to find any.

I know I can access the variables directly in the expression engine as well, but I would like to be able to retrieve the value within the python function and further do something with it.

---

Slightly modified the code, but it will still be nice to know if there is a single function that can return values of any variable, whether layer, project or global.

from qgis.core import *
from qgis.gui import *

from qgis.utils import *

@qgsfunction(args='auto', group='Custom')
def env1(var_name, feature, parent):
    """ Returns the value of the variable 'var_name' 
        Example usage: env('user_full_name') """
    active_layer = iface.activeLayer()
    return QgsExpressionContextScope.variable(QgsExpressionContextUtils.layerScope(active_layer), var_name) \
         or QgsExpressionContextScope.variable(QgsExpressionContextUtils.projectScope(), var_name) \
         or QgsExpressionContextScope.variable(QgsExpressionContextUtils.globalScope(), var_name)

Answer

Not completely sure but I think you could shorten your code again ever so slightly by just calling QgsExpressionContextUtils for the project and global scopes:

from qgis.core import *
from qgis.gui import *
from qgis.utils import *

@qgsfunction(args='auto', group='Custom')
def env1(var_name, feature, parent):
    """ Returns the value of the variable 'var_name' 
        Example usage: env('user_full_name') """

    active_layer = iface.activeLayer()
    return QgsExpressionContextScope.variable(QgsExpressionContextUtils.layerScope(active_layer), var_name) \
         or QgsExpressionContextUtils.projectScope().variable(var_name) \
         or QgsExpressionContextUtils.globalScope().variable(var_name)