两个代码有什么区别？

Question

What are the differences between the last lines? Why the second one is correct, and the first one is not? Instead, it seems normal.

# I wanted to write this code like this but it is false.Because of
# line 7 and 8.
def is_authorized(my_list,m_name):
    for num in range(len(my_list)):
        if my_list[num].name==m_name and my_list[num].authorized==True:
            return True
        else:
            return False


# program accepts this one. If indentation of line 16 same as line
# 13.

def is_authorized(my_list,m_name):
    for num in range(len(my_list)):
        if my_list[num].name==m_name and my_list[num].authorized==True:
            return True
    return False

Answer 1

First code

---

The first code would check only the first item, since it will return a value ( True or False ) even if the if condition is false.

while True:
    if (condition):
        return True
    else:
        return False

As you can see above, the loop will be executed only once.

Second code

---

You will check all the array, and return False only if the condition is false for each num in range(len(my_list)) .

while True:
    if (condition):
        return True
    return False

You second code has applications really similar to the any() built-in function.

Any

---

The Python built-in function any() , linked above, is used like this:

>>> any([True, False, True])
True
>>> any([False, False])
False
>>> array = [1, 2, 3, 4]
>>> booleans = [element > 2 for element in array]
>>> any(booleans)

In your case, you can do something like the code suggested by jak123:

def is_authorized(my_list,m_name):
    return any(
        item.name == m_name and item.authorized
        for item in my_list
   )

Answer 2

As mentioned, the for loop returns after the first item in the first case. Consider simplifying your code:

def is_authorized(my_list,m_name):
    return any(
        item.name == m_name and item.authorized
        for item in my_list
   )