KeyError的Python原因

Question

What I should to do, to avoid Keyerror in my code, I'm a noob :) I load json and print all the values ​​from the array by tag status_name , but the algorithm fails on an Keyerror , how can I handle it and then save the resulting list to a file?

import json
with open(r'.json', encoding='utf-8') as fp:
    data = json.load(fp)

for data in data:
    print(data['status_name'])

I get data from all tags status_name on request, but when the request reaches a tag where is no tag status_name , I get:

Traceback (most recent call last):
line 6, in <module>
KeyError: 'status_name'

Print Output:
v
v
v
m
u
u
m
v
v
v
v

I want to print none or skip such blocks

Answer 1

It seems like your data has no key named 'status_name'. Try printing only the data first, and see what is the actual key for what you're looking for.

As for saving it in a file, you can open a file with the 'w' mode, and write the data at the end of the loop. Like this:

file = open(data.txt, 'w')

for d in data:

print(d['status_name'])

file.write(d)

I changed 'data' for 'd' cause it was a bit confusing.

And don't forget to close the file after the loop.

Answer 2

There are two ways of handling the error:

Method 1

import json

with open(r'.json', encoding='utf-8') as fp:
    data = json.load(fp)

new_data = []
for d in data: # use different variable name
    # is d a dictionary and does it have 'status_name' as a key?
    if isinstance(d, dict) and 'status_name' in d:
        new_data.append(d)

"""    
# the above loop can be reduced to the more "Pythonic" list comprehension:
new_data = [d for d in data if isinstance(d, dict) and 'status_name' in d]
"""
with open('new_json', 'w', encoding='utf-8') as fp:
    json.dump(new_data, fp)

Method 2

import json

with open('.json', encoding='utf-8') as fp:
    data = json.load(fp)

new_data = []
for d in data: # use different variable name
    # assume d is a dictionary with key 'status_name'
    try:
        value = d['status_name']
    except Exception:
        pass # don't append d
    else:
        new_data.append(d) # no exception so append d

with open('new_json', 'w', encoding='utf-8') as fp:
    json.dump(new_data, fp)
    

Answer 3

import xlwt
import json
with open(r'name.json', encoding='utf-8') as fp:
    data = json.load(fp)
channels = set() # unique data
for item in data['items']: 
    if 'status_name' in item: #checking if there is a tag, bypass Keyerror
        channels.add(item['status_name'])
        print(item['status_name'])
print(channels) # print unique data

workbook = xlwt.Workbook()
sheet = workbook.add_sheet("Sheet Name")
# Writing on specified sheet
sheet.write(0, 0, 'Channels')
row = 1
for channel in sorted(channels):
    sheet.write(row, 0, channel)
    row += 1
workbook.save("name.xls")