用json.tool验证和美化json数据

python标准库json模块内有一个tool工具，可以用来验证json数据，并对json数据进行美化输出。

$ python3.8 -m json.tool msg.json
{
    "fromaddr": "from@qq.com",
    "passwd": "123456789",
    "server": "smtp.qq.com",
    "port": 587,
    "connect": "tls",
    "msg": [
        {
            "subject": "test json file",
            "to": "to@qq.com",
            "cc": null,
            "bcc": null,
            "content": "hahaha...lalala..."
        },
        {
            "subject": "test json file",
            "to": "to@qq.com",
            "cc": null,
            "bcc": null,
            "content": "2222...hahaha...lalala..."
        }
    ]
}

json.tool工具还有两个参数：--sort-key和--json-lines，具体请用-h查看说明。

json.tool的源码很简单，具体如下：

r"""Command-line tool to validate and pretty-print JSON

Usage::

    $ echo '{"json":"obj"}' | python -m json.tool
    {
        "json": "obj"
    }
    $ echo '{ 1.2:3.4}' | python -m json.tool
    Expecting property name enclosed in double quotes: line 1 column 3 (char 2)

"""
import argparse
import json
import sys


def main():
    prog = 'python -m json.tool'
    description = ('A simple command line interface for json module '
                   'to validate and pretty-print JSON objects.')
    parser = argparse.ArgumentParser(prog=prog, description=description)
    parser.add_argument('infile', nargs='?',
                        type=argparse.FileType(encoding="utf-8"),
                        help='a JSON file to be validated or pretty-printed',
                        default=sys.stdin)
    parser.add_argument('outfile', nargs='?',
                        type=argparse.FileType('w', encoding="utf-8"),
                        help='write the output of infile to outfile',
                        default=sys.stdout)
    parser.add_argument('--sort-keys', action='store_true', default=False,
                        help='sort the output of dictionaries alphabetically by key')
    parser.add_argument('--json-lines', action='store_true', default=False,
                        help='parse input using the jsonlines format')
    options = parser.parse_args()

    infile = options.infile
    outfile = options.outfile
    sort_keys = options.sort_keys
    json_lines = options.json_lines
    with infile, outfile:
        try:
            if json_lines:
                objs = (json.loads(line) for line in infile)
            else:
                objs = (json.load(infile), )
            for obj in objs:
                json.dump(obj, outfile, sort_keys=sort_keys, indent=4)
                outfile.write('\n')
        except ValueError as e:
            raise SystemExit(e)


if __name__ == '__main__':
    try:
        main()
    except BrokenPipeError as exc:
        sys.exit(exc.errno)

-- EOF --

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