Let's have a function make_sandwich that takes a list of ingredients which has a default value of ['ham', 'ham', 'bacon', 'ham']
def make_sandwich(ingredients=['ham', 'ham', 'bacon', 'ham']):
print("Making a sandwich with ", ingredients)
However, since this default value is susceptible to this python "mutable default argument" bug feature, we should use an immutable instead like this:
def make_sandwich(ingredients=None):
# initialized ingredients here
print("Making a sandwich with ", ingredients)
So here's the question. There're two ways that I am aware of to do this, but I am not sure which one is considered a better practice.
The first one:
if not ingredients:
ingredients = ['ham', 'ham', 'bacon', 'ham']
The second one:
ingredients = ingredients or ['ham', 'ham', 'bacon', 'ham']
Personally I use the second one more often. Sometimes, I even inline that if the argument is used only once. e.g.
print("Making a sandwich with ", ingredients or ['ham', 'ham', 'bacon', 'ham'])
Is there any solid reason to prefer one over the others?
None of them is actually the right way to do. What if you want to pass an empty list of ingredients?
A better solution would be
ingredients = ['ham', 'bacon', 'ham'] if ingredients is None else ingredients