使用python将数据导出到csv时出错

Question

I tried to export data to csv from Mongodb by using Python. I am getting error: "TypeError: can only join an iterable"

mongodb data sample:

{ "_id" : ObjectId("51dc52fec0d988a9547b5201"),
  "hiringManagerIds" : [ 
        "529f5ad1030dedd0a88ed7be", 
        "529f5ad1030dedd0a88ed7bf"
    ]
  }

Python script:

import codecs
import csv
cursor = db.jobs.find( {}, {'_id': 1, 'hiringManagerIds': 1})
with codecs.open('jobs_array.csv', 'w', encoding ='utf-8') as outfile:
    fields = ['_id', 'hiringManagerIds']    
    write = csv.writer(outfile)
    write.writerow(fields)
    for x in cursor:
        write.writerow((x["_id"], u','.join(x.get('hiringManagerIds'))))

error messages:

Traceback (most recent call last):
File "<stdin>", line 6, in <module>
TypeError: can only join an iterable

I want to remove u letters so I use u.join in the script. the hiringManagerIds filed is missing in some document, so I use get. If I don't add u''.join in the script, it works, but it brings u letters in the csv file. I tried many different ways, but it did not work. Appreciate for any helps. thanks.

Answer 1

The error stems from one of the documents not having hiringManagerIds. If this is undefined, at present your code returns None into the join method, which requires an iterable (None is not an iterable).

You should check if the key is present in the dictionary first:

if 'hiringManagerIds' in x.keys():
    write.writerow((x["_id"], u','.join(x.get('hiringManagerIds'))))
else:
    write.writerow((x["_id"], '')))