from lazy_object_proxy import Proxy

value = Proxy(lambda: expr())
# If this could be written in a more concise form. e.g.:
value = `expr()`
# then it would be worthwhile constructing and making use of VB-like expressions
def IF(condition, when_true, when_false):
    if condition:
        return when_true
    else:
        return when_false

def expr1():
    print('__expr1__')
    return 1

def expr2():
    print('__expr2__')
    return 2

result = IF(True, `expr1()`, `expr2()`)
# Expressions would only be evaluated when certain usage takes place

# This works fairly nicely, but inconvenience of it is a dealbreaker (to be used for such cases)
result = IF(True, Proxy(lambda: expr1()), Proxy(lambda: expr2()))
# Not yet evaluated
print(result + 1)
# Now it is

def IF(condition, when_true, when_false):
    if condition:
        return ensure_eval(when_true)
    else:
        return ensure_eval(when_false)