在Python中添加字典条目并追加到JSON文件的最佳方法

Question

I have a need to add entries to a dictionary with the following keys:

name
element
type

I want each entry to append to a JSON file, where I will access them for another piece of the project.

What I have below technically works, but there are couple things(at least) wrong with this.

First, it doesn't prevent duplicates being entered. For example I can have 'xyz', '4444' and 'test2' appear as JSON entries multiple times. Is there a way to correct this?

Is there a cleaner way to write the actual data entry piece so when I am entering these values into the dictionary it's not directly there in the parentheses?

Finally, is there a better place to put the JSON piece? Should it be inside the function?

Just trying to clean this up a bit. Thanks

import json

element_dict = {}


def add_entry(name, element, type):

        element_dict["name"] = name
        element_dict["element"] = element
        element_dict["type"] = type
        return element_dict


#add entry
entry = add_entry('xyz', '4444', 'test2')


#export to JSON
with open('elements.json', 'a', encoding="utf-8") as file:
    x = json.dumps(element_dict, indent=4)
    file.write(x + '\n')

Answer 1

There are several questions here. The main points worth mentioning:

• Use can use a list to hold your arguments and use *args to unpack when you supply them to add_entry .
• To check / avoid duplicates, you can use set to track items already added.
• For writing to JSON, now you have a list, you can simply iterate your list and write in one function at the end.

Putting these aspects together:

import json

res = []
seen = set()

def add_entry(res, name, element, type):

    # check if in seen set
    if (name, element, type) in seen:
        return res

    # add to seen set
    seen.add(tuple([name, element, type]))

    # append to results list
    res.append({'name': name, 'element': element, 'type': type})

    return res

args = ['xyz', '4444', 'test2']

res = add_entry(res, *args)  # add entry - SUCCESS
res = add_entry(res, *args)  # try to add again - FAIL

args2 = ['wxy', '3241', 'test3']

res = add_entry(res, *args2)  # add another - SUCCESS

Result:

print(res)

[{'name': 'xyz', 'element': '4444', 'type': 'test2'},
 {'name': 'wxy', 'element': '3241', 'type': 'test3'}]

Writing to JSON via a function:

def write_to_json(lst, fn):
    with open(fn, 'a', encoding='utf-8') as file:
        for item in lst:
            x = json.dumps(item, indent=4)
            file.write(x + '\n')

#export to JSON
write_to_json(res, 'elements.json')

Answer 2

you can try this way

import json
import hashlib


def add_entry(name, element, type):
        return {hashlib.md5(name+element+type).hexdigest(): {"name": name, "element": element, "type": type}}


#add entry
entry = add_entry('xyz', '4444', 'test2')


#Update to JSON
with open('my_file.json', 'r') as f:
    json_data = json.load(f)
    print json_data.values() # View Previous entries
    json_data.update(entry)

with open('elements.json', 'w') as f:
    f.write(json.dumps(json_data))