How to return object when using `append` in Python-CodePudding

i have a function to append a list, something like this:

def append_func(element):
    if xxxx:
        new_list.append(element)
    else:
        []

I have another function that uses append_func():

def second_func(item):
  for i in item:
     append_func(i)

if i run :

new_list = []
second _func(item)
new_list

This will return the list i want, but i can't do new_list = second _func(item) because in this case new_list will be a None.

I understand that append() will return a None type, but i'd like to return the appended list so I can use in other places result = second _func(xxx), what i have missed? Thanks.

CodePudding user response：

simply tell python what to return:

def append_func(element):
    if xxxx:
        new_list.append(element)
    else:
        []
    return new_list   # here, return whatever you want to return

if there is no "return" statement in the function, then the function returns None

CodePudding user response：

The new_list you define before calling second_func is a global variable. Every time you call second_func() it will append the argument to the global variable. But the new_list is not restricted to the namespace of either function, so setting it as a return value doesn't make sense.

CodePudding user response：

According to the clarification you did in the comments you might want something like this. (I changed some of your placeholders so we have running code and a reproducible example)

The list is created by second_func so we get rid of the global list.

def append_func(data, element):
    if 2 < element < 7:
        data.append(element ** 2)


def second_func(items):
    new_list = []
    for i in items:
        append_func(new_list, i)
    return new_list


items = list(range(10))
result = second_func(items)
print(result)

The result is [9, 16, 25, 36].