在 python def 语句中，是否可以在一行中编写 for 循环和 return 语句？

Question

# code 1
def x():
    for i in range(3):
        print(i)
    return None

# code 2
def x():
    for i in range(3): print(i); return None

# code 3
def x():
    for i in range(3):
        print(i)
        return None

# code 4
def x():
    for i in range(3): print(i)
    return None

Hello. I was testing about one line statements in Python. PEP 8 doesn't recommend this, but I wonder if it's possible.

I initially tried to write code 1 in one line like code 2. However, I found that the function ended in the first loop and realized that code 2 was the same as code 3. And I've reached the code 4.

However, I wonder if it's possible to abbreviate code 4 more and write it in one line.

---

Thank you for answering. That's right. The return None is virtually meaningless because it can be omitted. I needed to write the questions more carefully. But what if you want to return a processed value other than None as below? I abbreviated code 1 to code 2.

# code 1
def x():
    processed_values = []
    for i in range(3):
        processed_values.append(i*2)
    return processed_values
print(x())

# code 2
def y():
    processed_values = []
    for i in range(3): processed_values.append(i*2)
    return processed_values
print(y())

Answer 1

Firstly, you don't need to specifically call return None as this is done automatically. This saves us one line by default. Secondly, you can create lambda functions which are one-liner functions.

x = lambda num: [print(i) for i in range(num)]

# then calling your new function as normal
x(3)

This is functionally equivalent to:

def x(num):
    [print(i) for i in range(num)]

Answer 2

You can do this using list comprehension.

def code5():
    [print(i) for i in range(3)]; return None

The return statement here does not do anything much. So you can totally avoid it.

But most importantly, don't write code like this in any production application. This kind of coding is only going to make the things complicated and harder to understand.