unpacking_keyword_args.py

c_num = 10
d_num = 0

def do_something(a, b, c=0, d=0):
    return a + b + c + d

if d_num > 0:
    print(do_something(1, 2, c=c_num, d=d_num))
else:
    print(do_something(1, 2, c=c_num))

##################################

unpack = {}
unpack['c'] = 10

if d_num > 0:
    unpack['d'] = d_num

print(do_something(1, 2, **unpack))


##################################


# in Python 3
def do_something3(a, b, *, c=0, d=0):
    return a + b + c + d