在函数参数python中传递多个字典

Question

I have a function which takes more than one dictionary as its parameter. I am having an issue with Syntax as i keep getting the following message:

SyntaxError: non-keyword arg after keyword arg

Essentially , my code will run through each item in the file_names list and grab the file size for each one to be passed on my compare() function. I am having issues with passing multiple dictionaries. There are two keys for each dictionary and they are File Name and File Size. My code is as follows :

def compare(previous,current):

    tolerance = 0.4

    if previous is None and current is None:
        return " missing in both"

    if previous is None:
        return " new"

    if current is None:
        return " missing"

    size_ratio = float(current)/previous

    if size_ratio >= 1 + tolerance:
        return " %d%% bigger" % round(((size_ratio - 1) * 100),0)

    if size_ratio <= 1 - tolerance:
        return " %d%% smaller" % round(((1 - size_ratio) * 100),0)

    return " ok"


def compare_filesets(file_names, previous_data, current_data):


    for item in file_names:

     print (item + compare(previous_data.get('File Size'), current_data.get('File Size')) + "\n")



compare_filesets(file_names=['a.json', 'b.json', 'c.json'],
                 current_data= {"File Name": "a.json", "File Size": 1000}, {"File Name": "a.json", "File Size": 1000},
                 previous_data={"File Name": "a.json", "File Size": 1000}, {"File Name": "a.json", "File Size": 1000})

Answer 1

An argument is a single object, so func(arg1={}, {}) is not passing two dicts as "arg1" but one dict as (named argument) "arg1" and the second as a positional argument - and as you noticed, python forbids passing positional arguments after named ones (since it cannot know which parameter the positional argument would match).

If you want to pass more than one dict as "previous_data" and "current_data", you have to pass a collection of dict (in this cas a list is the very obvious choice), ie:

somefunc(a=[{}, {}], b=[{}, {}])

Now this also means you have to (re)write your functions in such a way that it expects lists of dicts, not dicts.