[英]Convert nested JSON to CSV file in Python
我知道这个问题已经被问过很多次了。 我尝试了几种解决方案,但无法解决我的问题。
我有一个大的嵌套 JSON 文件 (1.4GB),我想把它弄平,然后将其转换为 CSV 文件。
JSON 结构是这样的:
{
"company_number": "12345678",
"data": {
"address": {
"address_line_1": "Address 1",
"locality": "Henley-On-Thames",
"postal_code": "RG9 1DP",
"premises": "161",
"region": "Oxfordshire"
},
"country_of_residence": "England",
"date_of_birth": {
"month": 2,
"year": 1977
},
"etag": "26281dhge33b22df2359sd6afsff2cb8cf62bb4a7f00",
"kind": "individual-person-with-significant-control",
"links": {
"self": "/company/12345678/persons-with-significant-control/individual/bIhuKnFctSnjrDjUG8n3NgOrl"
},
"name": "John M Smith",
"name_elements": {
"forename": "John",
"middle_name": "M",
"surname": "Smith",
"title": "Mrs"
},
"nationality": "Vietnamese",
"natures_of_control": [
"ownership-of-shares-50-to-75-percent"
],
"notified_on": "2016-04-06"
}
}
我知道使用pandas
模块很容易完成,但我不熟悉它。
已编辑
所需的输出应该是这样的:
company_number, address_line_1, locality, country_of_residence, kind,
12345678, Address 1, Henley-On-Thamed, England, individual-person-with-significant-control
请注意,这只是简短版本。 输出应包含所有字段。
请向下滚动以获取更新、更快的解决方案
这是一个较旧的问题,但我整晚都在为类似的情况苦苦挣扎以获得满意的结果,我想出了这个:
import json
import pandas
def cross_join(left, right):
return left.assign(key=1).merge(right.assign(key=1), on='key', how='outer').drop('key', 1)
def json_to_dataframe(data_in):
def to_frame(data, prev_key=None):
if isinstance(data, dict):
df = pandas.DataFrame()
for key in data:
df = cross_join(df, to_frame(data[key], prev_key + '.' + key))
elif isinstance(data, list):
df = pandas.DataFrame()
for i in range(len(data)):
df = pandas.concat([df, to_frame(data[i], prev_key)])
else:
df = pandas.DataFrame({prev_key[1:]: [data]})
return df
return to_frame(data_in)
if __name__ == '__main__':
with open('somefile') as json_file:
json_data = json.load(json_file)
df = json_to_dataframe(json_data)
df.to_csv('data.csv', mode='w')
解释:
cross_join函数是我发现做笛卡尔积的一种巧妙方法。 (信用: 这里)
json_to_dataframe函数使用pandas 数据帧执行逻辑。 在我的情况下,json 是深度嵌套的,我想将字典key:value 对拆分为列,但是我想将列表转换为列的行- 因此是 concat - 然后我将其与上层交叉连接级别,从而乘以记录数,以便列表中的每个值都有自己的行,而前面的列是相同的。
递归创建与下面一个交叉连接的堆栈,直到返回最后一个。
然后使用表格格式的数据框,可以使用“df.to_csv()”数据框对象方法轻松转换为 CSV。
这应该适用于深度嵌套的 JSON,能够通过上述逻辑将所有数据规范化为行。
我希望有一天这会帮助某人。 只是想回馈这个很棒的社区。
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稍后编辑:新解决方案
我回到这个问题,因为虽然数据框选项有点工作,但应用程序花了几分钟来解析不是那么大的 JSON 数据。 因此,我想到做数据帧所做的事情,但我自己:
from copy import deepcopy
import pandas
def cross_join(left, right):
new_rows = [] if right else left
for left_row in left:
for right_row in right:
temp_row = deepcopy(left_row)
for key, value in right_row.items():
temp_row[key] = value
new_rows.append(deepcopy(temp_row))
return new_rows
def flatten_list(data):
for elem in data:
if isinstance(elem, list):
yield from flatten_list(elem)
else:
yield elem
def json_to_dataframe(data_in):
def flatten_json(data, prev_heading=''):
if isinstance(data, dict):
rows = [{}]
for key, value in data.items():
rows = cross_join(rows, flatten_json(value, prev_heading + '.' + key))
elif isinstance(data, list):
rows = []
for i in range(len(data)):
[rows.append(elem) for elem in flatten_list(flatten_json(data[i], prev_heading))]
else:
rows = [{prev_heading[1:]: data}]
return rows
return pandas.DataFrame(flatten_json(data_in))
if __name__ == '__main__':
json_data = {
"id": "0001",
"type": "donut",
"name": "Cake",
"ppu": 0.55,
"batters":
{
"batter":
[
{"id": "1001", "type": "Regular"},
{"id": "1002", "type": "Chocolate"},
{"id": "1003", "type": "Blueberry"},
{"id": "1004", "type": "Devil's Food"}
]
},
"topping":
[
{"id": "5001", "type": "None"},
{"id": "5002", "type": "Glazed"},
{"id": "5005", "type": "Sugar"},
{"id": "5007", "type": "Powdered Sugar"},
{"id": "5006", "type": "Chocolate with Sprinkles"},
{"id": "5003", "type": "Chocolate"},
{"id": "5004", "type": "Maple"}
],
"something": []
}
df = json_to_dataframe(json_data)
print(df)
输出:
id type name ppu batters.batter.id batters.batter.type topping.id topping.type
0 0001 donut Cake 0.55 1001 Regular 5001 None
1 0001 donut Cake 0.55 1001 Regular 5002 Glazed
2 0001 donut Cake 0.55 1001 Regular 5005 Sugar
3 0001 donut Cake 0.55 1001 Regular 5007 Powdered Sugar
4 0001 donut Cake 0.55 1001 Regular 5006 Chocolate with Sprinkles
5 0001 donut Cake 0.55 1001 Regular 5003 Chocolate
6 0001 donut Cake 0.55 1001 Regular 5004 Maple
7 0001 donut Cake 0.55 1002 Chocolate 5001 None
8 0001 donut Cake 0.55 1002 Chocolate 5002 Glazed
9 0001 donut Cake 0.55 1002 Chocolate 5005 Sugar
10 0001 donut Cake 0.55 1002 Chocolate 5007 Powdered Sugar
11 0001 donut Cake 0.55 1002 Chocolate 5006 Chocolate with Sprinkles
12 0001 donut Cake 0.55 1002 Chocolate 5003 Chocolate
13 0001 donut Cake 0.55 1002 Chocolate 5004 Maple
14 0001 donut Cake 0.55 1003 Blueberry 5001 None
15 0001 donut Cake 0.55 1003 Blueberry 5002 Glazed
16 0001 donut Cake 0.55 1003 Blueberry 5005 Sugar
17 0001 donut Cake 0.55 1003 Blueberry 5007 Powdered Sugar
18 0001 donut Cake 0.55 1003 Blueberry 5006 Chocolate with Sprinkles
19 0001 donut Cake 0.55 1003 Blueberry 5003 Chocolate
20 0001 donut Cake 0.55 1003 Blueberry 5004 Maple
21 0001 donut Cake 0.55 1004 Devil's Food 5001 None
22 0001 donut Cake 0.55 1004 Devil's Food 5002 Glazed
23 0001 donut Cake 0.55 1004 Devil's Food 5005 Sugar
24 0001 donut Cake 0.55 1004 Devil's Food 5007 Powdered Sugar
25 0001 donut Cake 0.55 1004 Devil's Food 5006 Chocolate with Sprinkles
26 0001 donut Cake 0.55 1004 Devil's Food 5003 Chocolate
27 0001 donut Cake 0.55 1004 Devil's Food 5004 Maple
根据上面所做的, cross_join函数的作用与数据帧解决方案中的几乎相同,但没有数据帧,因此速度更快。
我添加了flatten_list生成器,因为我想确保 JSON 数组都很好且扁平化,然后作为单个字典列表提供,其中包含一次迭代中的前一个键,然后分配给每个列表的值。 在这种情况下,这几乎模仿了pandas.concat 的行为。
主函数json_to_dataframe 中的逻辑与之前相同。 所有需要改变的是让数据帧执行的操作作为编码函数。
此外,在数据帧解决方案中,我没有将前一个标题附加到嵌套对象,但除非您 100% 确定列名没有冲突,否则它几乎是强制性的。
我希望这有帮助 :)。
编辑:修改了cross_join函数来处理嵌套列表为空的情况,基本保持之前的结果集不变。 即使在示例 JSON 数据中添加空 JSON 列表后,输出也不会改变。 谢谢@ Nazmus Sakib指出。
对于您提供的 JSON 数据,您可以通过解析 JSON 结构以仅返回所有叶节点的列表来执行此操作。
这假设您的结构始终保持一致,如果每个条目可以有不同的字段,请参阅第二种方法。
例如:
import json
import csv
def get_leaves(item, key=None):
if isinstance(item, dict):
leaves = []
for i in item.keys():
leaves.extend(get_leaves(item[i], i))
return leaves
elif isinstance(item, list):
leaves = []
for i in item:
leaves.extend(get_leaves(i, key))
return leaves
else:
return [(key, item)]
with open('json.txt') as f_input, open('output.csv', 'w', newline='') as f_output:
csv_output = csv.writer(f_output)
write_header = True
for entry in json.load(f_input):
leaf_entries = sorted(get_leaves(entry))
if write_header:
csv_output.writerow([k for k, v in leaf_entries])
write_header = False
csv_output.writerow([v for k, v in leaf_entries])
如果您的 JSON 数据是您提供的格式的条目列表,那么您应该得到如下输出:
address_line_1,company_number,country_of_residence,etag,forename,kind,locality,middle_name,month,name,nationality,natures_of_control,notified_on,postal_code,premises,region,self,surname,title,year
Address 1,12345678,England,26281dhge33b22df2359sd6afsff2cb8cf62bb4a7f00,John,individual-person-with-significant-control,Henley-On-Thames,M,2,John M Smith,Vietnamese,ownership-of-shares-50-to-75-percent,2016-04-06,RG9 1DP,161,Oxfordshire,/company/12345678/persons-with-significant-control/individual/bIhuKnFctSnjrDjUG8n3NgOrl,Smith,Mrs,1977
Address 1,12345679,England,26281dhge33b22df2359sd6afsff2cb8cf62bb4a7f00,John,individual-person-with-significant-control,Henley-On-Thames,M,2,John M Smith,Vietnamese,ownership-of-shares-50-to-75-percent,2016-04-06,RG9 1DP,161,Oxfordshire,/company/12345678/persons-with-significant-control/individual/bIhuKnFctSnjrDjUG8n3NgOrl,Smith,Mrs,1977
如果每个条目可以包含不同(或可能缺少)的字段,那么更好的方法是使用DictWriter
。 在这种情况下,需要处理所有条目以确定可能的fieldnames
的完整列表,以便可以写入正确的标题。
import json
import csv
def get_leaves(item, key=None):
if isinstance(item, dict):
leaves = {}
for i in item.keys():
leaves.update(get_leaves(item[i], i))
return leaves
elif isinstance(item, list):
leaves = {}
for i in item:
leaves.update(get_leaves(i, key))
return leaves
else:
return {key : item}
with open('json.txt') as f_input:
json_data = json.load(f_input)
# First parse all entries to get the complete fieldname list
fieldnames = set()
for entry in json_data:
fieldnames.update(get_leaves(entry).keys())
with open('output.csv', 'w', newline='') as f_output:
csv_output = csv.DictWriter(f_output, fieldnames=sorted(fieldnames))
csv_output.writeheader()
csv_output.writerows(get_leaves(entry) for entry in json_data)
您可以使用 Pandas 库 json_normalize 函数将结构展平,然后随意处理。 例如:
import pandas as pd
import json
raw = """[{
"company_number": "12345678",
"data": {
"address": {
"address_line_1": "Address 1",
"locality": "Henley-On-Thames",
"postal_code": "RG9 1DP",
"premises": "161",
"region": "Oxfordshire"
},
"country_of_residence": "England",
"date_of_birth": {
"month": 2,
"year": 1977
},
"etag": "26281dhge33b22df2359sd6afsff2cb8cf62bb4a7f00",
"kind": "individual-person-with-significant-control",
"links": {
"self": "/company/12345678/persons-with-significant-control/individual/bIhuKnFctSnjrDjUG8n3NgOrl"
},
"name": "John M Smith",
"name_elements": {
"forename": "John",
"middle_name": "M",
"surname": "Smith",
"title": "Mrs"
},
"nationality": "Vietnamese",
"natures_of_control": [
"ownership-of-shares-50-to-75-percent"
],
"notified_on": "2016-04-06"
}
}]"""
data = json.loads(raw)
data = pd.json_normalize(data)
print(data.to_csv())
这给了你:
,company_number,data.address.address_line_1,data.address.locality,data.address.postal_code,data.address.premises,data.address.region,data.country_of_residence,data.date_of_birth.month,data.date_of_birth.year,data.etag,data.kind,data.links.self,data.name,data.name_elements.forename,data.name_elements.middle_name,data.name_elements.surname,data.name_elements.title,data.nationality,data.natures_of_control,data.notified_on
0,12345678,Address 1,Henley-On-Thames,RG9 1DP,161,Oxfordshire,England,2,1977,26281dhge33b22df2359sd6afsff2cb8cf62bb4a7f00,individual-person-with-significant-control,/company/12345678/persons-with-significant-control/individual/bIhuKnFctSnjrDjUG8n3NgOrl,John M Smith,John,M,Smith,Mrs,Vietnamese,['ownership-of-shares-50-to-75-percent'],2016-04-06
参考 Bogdan Mircea 的回答,
代码几乎达到了我的目的! 但是每当它在嵌套的 json 中遇到空列表时,它都会返回一个空数据帧。
您可以通过将其放入代码中轻松解决该问题
elif isinstance(data, list):
rows = []
if(len(data) != 0):
for i in range(len(data)):
[rows.append(elem) for elem in flatten_list(flatten_json(data[i], prev_heading))]
else:
data.append(None)
[rows.append(elem) for elem in flatten_list(flatten_json(data[0], prev_heading))]
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