连接列表时 int object 不可迭代？

Question

def get_fail_pass_average(number_list):
    for number in number_list:
        under_50_list = []
        over_50_list = []
        if number >= 50:
            over_50_list += list(number)
        else:
            under_50_list = under_50_list + list(number)

Hi there,

For this code, I am trying to add a number to the over_50_list if that number if over 50. However, I get an error message stating that the int object is not interable. But aren't I adding a list with another list? How can that produce an error?

(I haven't included all the code here; I'm just trying to understand why I can't add these two lists. The aim of this code is to produce a list which gives the average of the over 50 and at 50 marks and under 50 marks)

Answer 1

You problem isn't adding things to the existing list s. It's calling the list() constructor on a number. That doesn't work; list() expects to receive an iterable that it converts to a list , but numbers are not iterable.

You really just want the list.append method to add single elements to the end of the list , eg:

over_50_list.append(number)

but if you insist on making single element temporary list s for the purpose, or really like the += syntax (which expects an iterable, just like list() itself does), you could do:

over_50_list += [number]

which makes a list literal containing a single value, which can then be passed to += for concatenation (it's just less efficient when you're only adding a single value at a time, creating and destroying temporary list s unnecessarily, which append avoids).

Once you've fixed that, you'll find the list s never have more than one element; that's because you replace them with a new empty list each time you loop. Move the definitions above/outside the for loop so you only make one new list for each, then build them element by element.

Answer 2

Change the code to if you want to add all the numbers separately as lists:

def get_fail_pass_average(number_list):
    for number in number_list:
        under_50_list = []
         over_50_list = []
        if number >= 50:
            over_50_list += [number]
        else:
             under_50_list += [number]

But, if you want to add the numbers to the lists directly, you can do:

def get_fail_pass_average(number_list):
    for number in number_list:
        under_50_list = []
         over_50_list = []
        if number >= 50:
            over_50_list.append(number)
        else:
             under_50_list.append(number])

Simply, you are not allowed to do list(int)