Python：将结构化文本解析为CSV格式

Question

I want to convert plain structured text files to the CSV format using Python.

The input looks like this

[-------- 1 -------]
Version: 2
 Stream: 5
 Account: A
[...]
[------- 2 --------]
 Version: 3
 Stream: 6
 Account: B
[...]

The output is supposed to look like this:

Version; Stream; Account; [...]
2; 5; A; [...]
3; 6; B; [...]

Ie the input is structured text records delimited by [----<sequence number>----] and containing <key>: <values> -pairs and the ouput should be CSV containing one record per line.

I am able to retrive the <key>: <values> -pairs into CSV format via

colonseperated = re.compile(' *(.+) *: *(.+) *')
fixedfields = re.compile('(\d{3} \w{7}) +(.*)')

-- but I have trouble to recognize beginning and end of the structured text records and with the re-writing as CSV line-records. Furthermore I would like to be able to separate different type of records, ie distinguish between - say - Version: 2 and Version: 3 type of records.

Answer 1

Reading the list is not that hard:

def read_records(iterable):
    record = {}
    for line in iterable:
        if line.startswith('[------'):
            # new record, yield previous
            if record:
                yield record
            record = {}
            continue
        key, value = line.strip().split(':', 1)
        record[key.strip()] = value.strip()

    # file done, yield last record
    if record:
        yield record

This produces dictionaries from your input file.

From this you can produce CSV output using the csv module, specifically the csv.DictWriter() class :

# List *all* possible keys, in the order the output file should list them
headers = ('Version', 'Stream', 'Account', ...)

with open(inputfile) as infile, open(outputfile, 'wb') as outfile:
    records = read_records(infile)

    writer = csv.DictWriter(outfile, headers, delimiter=';')
    writer.writeheader()

    # and write
    writer.writerows(records)

Any header keys missing from a record will leave that column empty for that record. Any extra headers you missed will raise an exception; either add those to the headers tuple, or set the extrasaction keyword to the DictWriter() constructor to 'ignore' .