python - 如何在 Python 中使用键创建字典

Question

显然，这是初学者会问的问题。但是，我正在努力将键添加到我的字典中以纠正以下错误:

import csv, json, sys

def find_deep_value(d, key):
# Modified from https://stackoverflow.com/questions/48568649/convert-json-to-csv-using-python/48569129#48569129

    if key in d:
        return d[key]
    for k in d.keys():
        if isinstance(d[k], dict):
            for j in find_deep_value(d[k], key):
                return j

inputFile = open("pywu.cache.json", 'r')  # open json file
outputFile = open("CurrentObs.csv", 'w')  # load csv file
data = json.load(inputFile)  # load json content
inputFile.close()  # close the input file
output = csv.writer(outputFile)  # create a csv.write

# Gives you latitude coordinates from within the json
lat = find_deep_value(data, "latitude")

# Gives you longitude coordinates from within the json
lon = find_deep_value(data, "longitude")

# Gives you a list of weather from within the json
weather = find_deep_value(data, "weather")

# Gives you a list of temperature_strings from within the json
temp = find_deep_value(data, "temperature_string")

output.writerow([lat, lon, weather, temp])

返回错误，如下:

outputFile.close()
  File "json_to_csv.py", line 20, in <module>
    lat = find_deep_value(data, "latitude")
  File "json_to_csv.py", line 10, in find_deep_value
    for j in find_deep_value(d[k], key):
  File "json_to_csv.py", line 10, in find_deep_value
    for j in find_deep_value(d[k], key):
TypeError: 'NoneType' object is not iterable

我该如何解决这个问题？我尝试创建一个空字典“dict={}”并以这种方式添加，但仍然没有返回任何内容。

感谢所有帮助!

Answer 1

如果没有发现任何情况，您还需要处理该案件。因此，返回一个空字典而不是 None，即没有执行 return:

def find_deep_value(d, key):
    if key in d:
        return d[key]
    for k in d.keys():
        if isinstance(d[k], dict):
            for j in find_deep_value(d[k], key):
                return j
    return {}