Python: default dict keys to avoid KeyError

问题

Fairly new to python, novice developer, first time caller

I'm calling some JSON and parsing relevant data as csv. I cannot figure out how to fill in the intermediate json Dict file with default keys, as many are unpopulated. The result is a KeyError as I attempt to parse the content into a csv. Would love any advice!

Thanks.

Update: thanks everyone! I'm now receiving a 'NoneType' error for (manufacturer):

import urllib2, json, csv, sys, os, codecs, re

from collections import defaultdict

output = 'bb.csv'

csv_writer = csv.writer(open(output, 'w'))

header = ['sku', 'name', 'description', 'image', 'manufacturer', 'upc', 'department', 'class', 'subclass']

csv_writer.writerow(header)

i=1

while i<101:
    print i

    bb_url = urllib2.Request("http://api.remix.bestbuy.com/v1/products(sku=*)?show=sku,name,description,image,manufacturer,upc,department,class,subclass&format=json&sort=sku.asc&page=" + str(i) + "&pageSize=100&apiKey=*****************")
    bb_json = json.load(urllib2.urlopen(bb_url))

    print bb_json

    for product in bb_json['products']:
        row = []

        row.append(product['sku'])
        if product['name']:
            row.append(str((product['name']).encode('utf-8')))
        else:
            row.append("")
        row.append(str(product.get('description',"")))
        row.append(str(product['image'])+ " ")
        if product['name']:
            row.append(str(product.get('manufacturer',"").encode('utf-8')))
        else:
            row.append("")
        row.append(str(product.get('upc','').encode('utf-8')))
        row.append(str((product['department']).encode('utf-8')))
        row.append(str((product['class']).encode('utf-8')))
        row.append(str((product['subclass']).encode('utf-8')))

        csv_writer.writerow(row)

    i = i+1

回答1:

You can use your_dict.get(key, "default value") instead of directly referencing a key.

回答2:

Don't use the "default" argument name. For example, if we want 1.0 as default value,

rank = dict.get(key, 1.0)

For more details: TypeError: get() takes no keyword arguments

回答3:

If you can't define a default value and want to do something else (or just omit the entry):

if key in dict:
    rank = dict[key]
else:
    # do something or just skip the else block entirely

回答4:

You could use syntax like this: product.get("your field", "default value")

来源：https://stackoverflow.com/questions/24814024/python-default-dict-keys-to-avoid-keyerror

标签

python

json

csv

dictionary

keyerror