在文件上逐行写入词典列表

如果需要按特定顺序保存大量词典,为什么不先将它们放在列表对象中,然后使用json为您序列化整个过程?

import json


def example():
    # create a list of dictionaries
    list_of_dictionaries = [
        {'a': 0, 'b': 1, 'c': 2},
        {'d': 3, 'e': 4, 'f': 5},
        {'g': 6, 'h': 7, 'i': 8}
    ]

    # Save json info to file
    path = '.\\json_data.txt'
    save_file = open(path, "wb")
    json.dump(obj=list_of_dictionaries,
              fp=save_file)
    save_file.close()

    # Load json from file
    load_file = open(path, "rb")
    result = json.load(fp=load_file)
    load_file.close()

    # show that it worked
    print(result)
    return


if __name__ == '__main__':
    example()

如果您的应用程序必须不时附加新词典,则可能需要执行更接近以下内容的操作:

import json


def example_2():
    # create a list of dictionaries
    list_of_dictionaries = [
        {'a': 0, 'b': 1, 'c': 2},
        {'d': 3, 'e': 4, 'f': 5},
        {'g': 6, 'h': 7, 'i': 8}
    ]

    # Save json info to file
    path = '.\\json_data.txt'

    save_file = open(path, "w")
    save_file.write(u'[')
    save_file.close()

    first = True
    for entry in list_of_dictionaries:
        save_file = open(path, "a")
        json_data = json.dumps(obj=entry)
        prefix = u'' if first else u', '
        save_file.write(prefix + json_data)
        save_file.close()
        first = False

    save_file = open(path, "a")
    save_file.write(u']')
    save_file.close()

    # Load json from file
    load_file = open(path, "rb")
    result = json.load(fp=load_file)
    load_file.close()

    # show that it worked
    print(result)
    return


if __name__ == '__main__':
    example_2()