Python 如何用换行符读取字典文件？

Question

我有一个包含 json 个像这样的对象的文件

dict\n
dict\n
.
.
.

这就是我制作此文件的方式

with open(old_surveys.json, 'a+') as f1:
            for survey in data:
                surv = {"sid": survey["id"],
                    "svy_ttl": survey["title"]),
                    "svy_link": survey["href"]
                    }
                f1.seek(0)
                
                if str(surv["sid"]) not in f1.read():
                    json.dump(surv, f1)
                    f1.write('\n')
            f1.close()

现在我想检查文件 old_surveys.json 中是否有特定的字典。如何逐行阅读？

Answer 1

假设你有这样一个文件

{"sid": 1, "svy_ttl": "foo", "svy_link": "foo.com"}
{"sid": 2, "svy_ttl": "bar", "svy_link": "bar.com"}
{"sid": 3, "svy_ttl": "Alice", "svy_link": "alice.com"}
{"sid": 4, "svy_ttl": "Bob", "svy_link": "bob.com"}

这段代码怎么样？我不确定这是最佳解决方案

import json


def target_dict_exists(target_dict, filename):
    with open(filename, "r") as f:
        for line in f:
            if json.loads(line) == target_dict:
                return True
    return False


if __name__ == "__main__":
    target = {"sid": 3, "svy_ttl": "Alice", "svy_link": "alice.com"}
    print(target_dict_exists(target, "test.txt"))

Answer 2

为了更有效地避免重复，并回答您的问题：

import json

with open('old_surveys.json', 'a+') as f1:
    # first load all the old surveys in a dictionary
    f1.seek(0)
    surveys = {}
    for line in f1:
        d = json.loads(line)
        surveys[d['sid']] = d
    # then write any new ones from data
    for survey in data:
        if survey['id'] not in surveys:
            json.dump({'sid': survey['id'], 'svy_ttl': survey['title'], 'svy_link': survey['href']}, f1)
            f1.write('\n')
    # this line is not needed, it closes thanks to with
    # f1.close()

您可能还想创建 surv 并将其写入文件，并将其添加到 surveys，如果您希望 data 中有重复项。

import json

with open('old_surveys.json', 'a+') as f1:
    f1.seek(0)
    surveys = {}
    for line in f1:
        d = json.loads(line)
        surveys[d['sid']] = d
    for survey in data:
        if survey["id"] not in surveys:
            surv = {"sid": survey["id"], "svy_ttl": survey["title"], "svy_link": survey["href"]}
            surveys[surv['id']] = surv
            json.dump(surv, f1)
            f1.write('\n')

如果您真的不需要调查，而只需要标识符，这会更有效：

import json

with open('old_surveys.json', 'a+') as f1:
    f1.seek(0)
    surveys = set()
    for line in f1:
        d = json.loads(line)
        surveys.add(d['sid'])
    for survey in data:
        if survey["id"] not in surveys:
            surv = {"sid": survey["id"], "svy_ttl": survey["title"], "svy_link": survey["href"]}
            surveys.add(surv['id'])
            json.dump(surv, f1)
            f1.write('\n')

此处，字典已替换为 set()，因为您只需要跟踪标识符，但您将无法访问本节之后的其余调查（与之前不同).

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