函数列表在 Python 中是如何工作的？

Question

I saw a code (these functions are from sklearn module imports)

classifiers = [
    LinearDiscriminantAnalysis(),
    GaussianNB(),
    KNeighborsClassifier(3),
    SVC(kernel="linear", C=0.25),
    SVC(gamma=2, C=1),
    DecisionTreeClassifier(max_depth=2),
    AdaBoostClassifier(),
    ]

I was trying to understand what the above code does, so I tried playing with a small test

But, when I do this,

def function0():
    print("0")

def function1():
    print("1")

lst = [function0(), function1()]

for i in range(2):
    print(lst[i])

it prints,

0
1
None
None

I believe I understood the code wrong... Could anyone help me understand what I'm missing?

--------------------------------- edit -------------------------------

def function0():
    return 0

def function1():
    return 1

lst = [function0(), function1()]

for i in range(2):
    print(lst[i])

I figured out what I did wrong.

Answer 1

The problem is that you functions return nothing (which is assumed to be None when called).

You can try this instead:

def function0():
    print("0")

def function1():
    print("1")

lst = [function0, function1]

for func in lst:
    func()

Answer 2

I have modified the code so it will be easy to understand.
The 2 functions are called and print what they print.
Each function return None so the list is populated with 2 None values

def function0():
    print("0")
    return None


def function1():
    print("1")
    return None


lst = [function0(), function1()]
print('-------------------')
for i in range(2):
    print(lst[i])

output

0
1
-------------------
None
None