Small example on "global" variables and passing things "as reference"

varcheck.py

from sys import exit
from textwrap import fill as tw

fail = [False]
def varcheck(var_name, var_value, optional = False):
    is_empty = len(var_value) == 0
    if optional:
        symbol = "🔲"
    elif is_empty or "$(" in var_value:
        symbol = "❌"
        fail[0] = True
    else:
        symbol = "✔"
    print(tw(f"""{symbol} {var_name}{': ' if not is_empty else ''}{var_value}""", subsequent_indent='    '))

varcheck("foo1","bar1")
varcheck("foo2", "", optional=True)
varcheck("foo3", "$(SOMETHING)")
#varcheck("foo0","")

print('')
if fail[0]:
    print("FAIL")
else:
    print("PASS")
if fail[0]: exit(1)

from sys import exit
from textwrap import fill as tw

def varcheck(var_name, var_value, optional = False):
    is_empty = len(var_value) == 0
    fail = False
    if optional:
        symbol = "🔲"
    elif is_empty or "$(" in var_value:
        symbol = "❌"
        fail = True
    else:
        symbol = "✔"
    print(tw(f"""{symbol} {var_name}{': ' if not is_empty else ''}{var_value}""", subsequent_indent='    '))
    if fail:
        raise ValueError()

print()
try:
    varcheck("foo1","bar1")
    varcheck("foo2", "", optional=True)
    varcheck("foo3", "$(SOMETHING)")
    #varcheck("foo0","")
except ValueError:
    print("FAIL")
    exit(1)
print("PASS")

from sys import exit
from textwrap import fill as tw

def varcheck(var_name, var_value, optional = False):
    is_empty = len(var_value) == 0
    fail = False
    if optional:
        symbol = "🔲"
    elif is_empty or "$(" in var_value:
        symbol = "❌"
        fail = True
    else:
        symbol = "✔"
    print(tw(f"""{symbol} {var_name}{': ' if not is_empty else ''}{var_value}""", subsequent_indent='    '))
    return fail

print()
calls_results = [
    varcheck("foo1","bar1")
    varcheck("foo2", "", optional=True)
    varcheck("foo3", "$(SOMETHING)")
    #varcheck("foo0","")
]
if any(calls_results):
    print("FAIL")
    exit(1)
print("PASS")