对 Python 编程有点陌生，正在尝试一个问题。 我只是不知道为什么这个错误不断弹出。 对我来说真的没有意义

Question

This was the question: Create a function named add_greetings() which takes a list of strings named names as a parameter.

In the function, create an empty list that will contain each greeting. Add the string "Hello, " in front of each name in names and append the greeting to the list.

Return the new list containing the greetings.

Quite a basic question but I accidentally initialized the new list outside the function like this:

new_lst = []

def add_greetings(names):
    for name in names:
        name = "Hello, " + name
        new_lst.append(name)
    return new_lst

print(add_greetings(["Owen", "Max", "Sophie"]))

This was a question on Codecademy and it gave me this error:

add_greetings(["Owen", "Max", "Sophie"]) should have returned ['Hello, Owen', 'Hello, Max', 'Hello, Sophie'] , and it returned ['Hello, Owen', 'Hello, Max', 'Hello, Sophie', 'Hello, Owen', 'Hello, Owen', 'Hello, Max', 'Hello, Sophie']

Why is this the case? Tried it on the Python IDE, and it gave me the expected correct answer.

Answer 1

You should try instantiating the new_list inside the function:

def add_greetings(names):
    new_lst = []
    for name in names:
        name = "Hello, " + name
        new_lst.append(name)
    return new_lst

print(add_greetings(["Owen", "Max", "Sophie"]))

What ends up happening when Codeacademy tests it is they will run more than one test case. When you run your method more than once, it will continue appending to the same list over and over again, and will therefore return the wrong result. This can be mitigated by putting the list initialization inside the function itself, so you start fresh each time.