Question

How can I make a Python function default value be evaluated each time the function is called?
Take this dummy code:

b=0
def a():
    global b
    return b

def c(d=a()):
    return d

What I would expect as output:

>>> c()
0
>>> b=1
>>> a()
1
>>> c()
1

What I actually get:

>>> c()
0
>>> b=1
>>> a()
1
>>> c()
0

Answer 1

One more solution, in closer resemblance to your original answer.

b = 0
def a():
    return b

def c(d=a):    # When it's a parameter, the call will be evaluated and its return 
               # value will be used. Instead, just use the function name, because
    return d() # within the scope of the function, the call will be evaluated every time.

When a function name is paired with the parentheses and its parameters, like f(x), it is assumed your intention is to call it at that time