python脚本上的KeyError

Question

I have this script to delete files from my slack account:

import requests
import json
import calendar
import re
from datetime import datetime, timedelta

_token = re.escape("token")
_domain = re.escape("domain")

if __name__ == '__main__':
    while 1:
        files_list_url = 'https://slack.com/api/files.list'
        date = str(calendar.timegm((datetime.now() + timedelta(-30))
            .utctimetuple()))
        data = {"token": _token, "ts_to": date}
        response = requests.post(files_list_url, data = data)

        if len(response.json()["files"]) == 0:
            break
        for f in response.json()["files"]:
            print "Deleting file " + f["name"] + "..."
            timestamp = str(calendar.timegm(datetime.now().utctimetuple()))
            delete_url = "https://" + _domain + ".slack.com/api/files.delete?t=" + timestamp
            requests.post(delete_url, data = {
                "token": _token, 
                "file": f["id"], 
                "set_active": "true", 
                "_attempts": "1"})
    print "DONE!"

Im getting this error:

File "main.py", line 28, in files = json.loads(content)["files"] KeyError: 'files'

Am i missing something? Tks!

Answer 1

Switch

if len(response.json()["files"]) == 0:

To

if len(response.json().get("files", [])) == 0:

By default, the get method returns None if the attribute doesn't exist, whereas the [] notation throws up an error if the item doesn't exist. If the response.json() doesn't have a files attribute (which is what's happening here) then it will break out.

Answer 2

You're expecting that json.loads() will return a dict that will have a key named files . But in reality, the parsed data doesn't have that key.

You can do these instead:

payload = json.loads(content)
files = payload.get('files')

This way files will either contain the actual files as in the JSON payload. If the files key does not exist, it will return None .

You can also pass a value to the get method to set the default value if the key is not found, like these:

files = payload.get('files', [])

This way files will be an empty list if the files key doesn't exist.