使用python基于公共字段合并2个csv文件

Question

I generated 2 csv files from 2 mysql tables. now I want to merge the 2 files together.

I manually added this header for the first csv:

ID,name,sector,sub_sector

and this is the second csv header:

ID,url

my goal is to have 1 file:

ID,name,sector,sub_sector,url

note: not whole records in the first file have a match in the second file.

this is the snippet I was using:

#!/usr/bin/env python
import glob, csv
if __name__ == '__main__':

    infiles = glob.glob('./*.csv')
    out = 'temp.csv'
    data = {}
    fields = []

    for fname in infiles:
        df = open(fname, 'rb')
        reader = csv.DictReader(df)
        for line in reader:
            # assuming the field is called ID
            if line['ID'] not in data:
                data[line['ID']] = line
            else:
                for k,v in line.iteritems():
                    if k not in data[line['ID']]:
                        data[line['ID']][k] = v
            for k in line.iterkeys():
                if k not in fields:
                    fields.append(k)
        del reader
        df.close()

    writer = csv.DictWriter(open(out, "wb"), fields, extrasaction='ignore', dialect='excel')
    # write the header at the top of the file
    writer.writeheader()
    writer.writerows(data)
    del writer

taken from another sof thread. and this is the error I'm getting:

  File "db_work.py", line 30, in <module>
    writer.writerows(data)
  File "/usr/lib/python2.7/csv.py", line 153, in writerows
    rows.append(self._dict_to_list(rowdict))
  File "/usr/lib/python2.7/csv.py", line 144, in _dict_to_list
    ", ".join(wrong_fields))
ValueError: dict contains fields not in fieldnames: 4, 4, 4, 6
~/Development/python/DB$ python db_work.py
Traceback (most recent call last):
  File "db_work.py", line 30, in <module>
    writer.writerows(data)
  File "/usr/lib/python2.7/csv.py", line 153, in writerows
    rows.append(self._dict_to_list(rowdict))
  File "/usr/lib/python2.7/csv.py", line 145, in _dict_to_list
    return [rowdict.get(key, self.restval) for key in self.fieldnames]
AttributeError: 'str' object has no attribute 'get'

any ideas how to fix this?

Answer 1

.writerows() expects a list , but you are passing in a dict instead. I think you wanted to write the values of data only:

writer = csv.DictWriter(open(out, "wb"), fields, dialect='excel')
# write the header at the top of the file
writer.writeheader()
writer.writerows(data.values())

Personally, I'd read the file with just the id, url rows, add those to a dict, then read the other file and write each row one at a time by adding the corresponding url entry.

import csv

with open('urls.csv', 'rb') as urls:
    reader = csv.reader(urls)
    reader.next()  # skip the header, won't need that here
    urls = {id: url for id, url in reader}

with open('other.csv', 'rb') as other:
    with open(out, 'wb') as output:
        reader = csv.reader(other)
        writer = csv.writer(output)
        writer.writerow(reader.next() + ['url'])  # read old header, add urls and write out
        for row in reader:
            # write out original row plus url if we can find one
            writer.writerow(row + [urls.get(row[0], '')])