示例 A-5 是 14.13 节讨论的 isis2json.py 脚本。这个脚本使用生成器函数，以惰性的方式把 CDS/ISIS 数据库转换成 JSON 格式，以便载入到 CouchDB 或 MongoDB。
注意，这是个 Python 2 脚本，针对 CPython 或 Jython，支持 Python 2.5~2.7，不能使用 Python 3 运行。在 CPython 中，只能读取 .iso 文件；在 Jython 中，使用 GitHub 中 fluentpython/isis2json 仓库（https://github.com/fluentpython/isis2json）里的 Bruma 库，还可以读取 .mst 文件。详情参见该仓库里的用法文档。
示例 A-5 isis2json.py：依赖和文档在 GitHub 中的 fluentpython/isis2json 仓库里
# 这个脚本支持Python和Jython（版本>=2.5且<3）
import sys
import argparse
from uuid import uuid4
import os
try:
import json
except ImportError:
if os.name == 'java': # 在Jython中运行
from com.xhaus.jyson import JysonCodec as json
else:
import simplejson as json
SKIP_INACTIVE = True
DEFAULT_QTY = 2**31
ISIS_MFN_KEY = 'mfn'
ISIS_ACTIVE_KEY = 'active'
SUBFIELD_DELIMITER = '^'
INPUT_ENCODING = 'cp1252'
def iter_iso_records(iso_file_name, isis_json_type): ➊
from iso2709 import IsoFile
from subfield import expand
iso = IsoFile(iso_file_name)
for record in iso:
fields = {}
for field in record.directory:
field_key = str(int(field.tag)) # 删除前导零
field_occurrences = fields.setdefault(field_key, [])
content = field.value.decode(INPUT_ENCODING, 'replace')
if isis_json_type == 1:
field_occurrences.append(content)
elif isis_json_type == 2:
field_occurrences.append(expand(content))
elif isis_json_type == 3:
field_occurrences.append(dict(expand(content)))
else:
raise NotImplementedError('ISIS-JSON type %s conversion '
'not yet implemented for .iso input' % isis_json_type)
yield fields
iso.close()
def iter_mst_records(master_file_name, isis_json_type): ➋
try:
from bruma.master import MasterFactory, Record
except ImportError:
print('IMPORT ERROR: Jython 2.5 and Bruma.jar '
'are required to read .mst files')
raise SystemExit
mst = MasterFactory.getInstance(master_file_name).open()
for record in mst:
fields = {}
if SKIP_INACTIVE:
if record.getStatus() != Record.Status.ACTIVE:
continue
else: # 仅当没有活动的记录时才保存状态
fields[ISIS_ACTIVE_KEY] = (record.getStatus() ==
Record.Status.ACTIVE)
fields[ISIS_MFN_KEY] = record.getMfn()
for field in record.getFields():
field_key = str(field.getId())
field_occurrences = fields.setdefault(field_key, [])
if isis_json_type == 3:
content = {}
for subfield in field.getSubfields():
subfield_key = subfield.getId()
if subfield_key == '*':
content['_'] = subfield.getContent()
else:
subfield_occurrences = content.setdefault(subfield_key, [])
subfield_occurrences.append(subfield.getContent())
field_occurrences.append(content)
elif isis_json_type == 1:
content = []
for subfield in field.getSubfields():
subfield_key = subfield.getId()
if subfield_key == '*':
content.insert(0, subfield.getContent())
else:
content.append(SUBFIELD_DELIMITER + subfield_key +
subfield.getContent())
field_occurrences.append(''.join(content))
else:
raise NotImplementedError('ISIS-JSON type %s conversion '
'not yet implemented for .mst input' % isis_json_type)
yield fields
mst.close()
def write_json(input_gen, file_name, output, qty, skip, id_tag, ➌
gen_uuid, mongo, mfn, isis_json_type, prefix,
constant):
start = skip
end = start + qty
if id_tag:
id_tag = str(id_tag)
ids = set()
else:
id_tag = ''
for i, record in enumerate(input_gen):
if i >= end:
break
if not mongo:
if i == 0:
output.write('[')
elif i > start:
output.write(',')
if start <= i < end:
if id_tag:
occurrences = record.get(id_tag, None)
if occurrences is None:
msg = 'id tag #%s not found in record %s'
if ISIS_MFN_KEY in record:
msg = msg + (' (mfn=%s)' % record[ISIS_MFN_KEY])
raise KeyError(msg % (id_tag, i))
if len(occurrences) > 1:
msg = 'multiple id tags #%s found in record %s'
if ISIS_MFN_KEY in record:
msg = msg + (' (mfn=%s)' % record[ISIS_MFN_KEY])
raise TypeError(msg % (id_tag, i))
else: # 好吧，有且仅有一个id字段
if isis_json_type == 1:
id = occurrences[0]
elif isis_json_type == 2:
id = occurrences[0][0][1]
elif isis_json_type == 3:
id = occurrences[0]['_']
if id in ids:
msg = 'duplicate id %s in tag #%s, record %s'
if ISIS_MFN_KEY in record:
msg = msg + (' (mfn=%s)' % record[ISIS_MFN_KEY])
raise TypeError(msg % (id, id_tag, i))
record['_id'] = id
ids.add(id)
elif gen_uuid:
record['_id'] = unicode(uuid4())
elif mfn:
record['_id'] = record[ISIS_MFN_KEY]
if prefix:
# 迭代一个固定的标签序列
for tag in tuple(record):
if str(tag).isdigit():
record[prefix+tag] = record[tag]
del record[tag] # 这就是迭代元组的原因
# 获取标签，但不直接从记录字典中获取
if constant:
constant_key, constant_value = constant.split(':')
record[constant_key] = constant_value
output.write(json.dumps(record).encode('utf-8'))
output.write('\n')
if not mongo:
output.write(']\n')
def main(): ➍
# 创建解析器
parser = argparse.ArgumentParser(
description='Convert an ISIS .mst or .iso file to a JSON array')
# 添加参数
parser.add_argument(
'file_name', metavar='INPUT.(mst|iso)',
help='.mst or .iso file to read')
parser.add_argument(
'-o', '--out', type=argparse.FileType('w'), default=sys.stdout,
metavar='OUTPUT.json',
help='the file where the JSON output should be written'
' (default: write to stdout)')
parser.add_argument(
'-c', '--couch', action='store_true',
help='output array within a "docs" item in a JSON document'
' for bulk insert to CouchDB via POST to db/_bulk_docs')
parser.add_argument(
'-m', '--mongo', action='store_true',
help='output individual records as separate JSON dictionaries, one'
' per line for bulk insert to MongoDB via mongoimport utility')
parser.add_argument(
'-t', '--type', type=int, metavar='ISIS_JSON_TYPE', default=1,
help='ISIS-JSON type, sets field structure: 1=string, 2=alist,'
' 3=dict (default=1)')
parser.add_argument(
'-q', '--qty', type=int, default=DEFAULT_QTY,
help='maximum quantity of records to read (default=ALL)')
parser.add_argument(
'-s', '--skip', type=int, default=0,
help='records to skip from start of .mst (default=0)')
parser.add_argument(
'-i', '--id', type=int, metavar='TAG_NUMBER', default=0,
help='generate an "_id" from the given unique TAG field number'
' for each record')
parser.add_argument(
'-u', '--uuid', action='store_true',
help='generate an "_id" with a random UUID for each record')
parser.add_argument(
'-p', '--prefix', type=str, metavar='PREFIX', default='',
help='concatenate prefix to every numeric field tag'
' (ex. 99 becomes "v99")')
parser.add_argument(
'-n', '--mfn', action='store_true',
help='generate an "_id" from the MFN of each record'
' (available only for .mst input)')
parser.add_argument(
'-k', '--constant', type=str, metavar='TAG:VALUE', default='',
help='Include a constant tag:value in every record (ex. -k type:AS)')
'''
# TODO: 实现这个功能，导出大量记录供给CouchDB
parser.add_argument(
'-r', '--repeat', type=int, default=1,
help='repeat operation, saving multiple JSON files'
' (default=1, use -r 0 to repeat until end of input)')
'''
# 解析命令行
args = parser.parse_args()
if args.file_name.lower().endswith('.mst'):
input_gen_func = iter_mst_records ➎
else:
if args.mfn:
print('UNSUPORTED: -n/--mfn option only available for .mst input.')
raise SystemExit
input_gen_func = iter_iso_records ➏
input_gen = input_gen_func(args.file_name, args.type) ➐
if args.couch:
args.out.write('{ "docs" : ')
write_json(input_gen, args.file_name, args.out, args.qty, ➑
args.skip, args.id, args.uuid, args.mongo, args.mfn,
args.type, args.prefix, args.constant)
if args.couch:
args.out.write('}\n')
args.out.close()
if __name__ == '__main__':
main()
❶ iter_iso_records 生成器函数读取 .iso 文件，产出记录。
❷ iter_mst_records 生成器函数读取 .mst 文件，产出记录。
❸ write_json 函数迭代 input_gen 生成器，输出 .json 文件。
❹ main 函数读取命令行参数，然后根据输入文件的扩展名选择……
❺ ……iter_mst_records 生成器函数……
❻ …… 或者 iter_iso_records 生成器函数。
❼ 使用选中的生成器函数构建生成器对象。
❽ 把生成器作为第一个参数传给 write_json 函数。