python - Flask 和 BytesIO:将文件输出为流的问题
问题描述
我正在尝试将生成的 Excel 文件作为 JSON 有效负载的文件流输出,如下所示:
def post(self):
keys = []
wb = Workbook()
ws = wb.active
json_data = request.get_json()
with NamedTemporaryFile() as tmp:
for i in range(len(json_data)):
sub_obj = json_data[i]
if i == 0:
keys = list(sub_obj.keys())
for k in range(len(keys)):
# row or column index start from 1
ws.cell(row=(i + 1), column=(k + 1), value=keys[k]);
for j in range(len(keys)):
ws.cell(row=(i + 2), column=(j + 1), value=sub_obj[keys[j]]);
wb.save(tmp.name)
output = BytesIO(tmp.read())
return output.getvalue()
但这会引发错误
Traceback (most recent call last):
File "/PythonAPI/flask/env/lib/python3.7/site-packages/flask/app.py", line 2464, in __call__
return self.wsgi_app(environ, start_response)
File "/PythonAPI/flask/env/lib/python3.7/site-packages/flask/app.py", line 2450, in wsgi_app
response = self.handle_exception(e)
File "/PythonAPI/flask/env/lib/python3.7/site-packages/flask_restful/__init__.py", line 272, in error_router
return original_handler(e)
File "/PythonAPI/flask/env/lib/python3.7/site-packages/flask/app.py", line 1867, in handle_exception
reraise(exc_type, exc_value, tb)
File "/PythonAPI/flask/env/lib/python3.7/site-packages/flask/_compat.py", line 38, in reraise
raise value.with_traceback(tb)
File "/PythonAPI/flask/env/lib/python3.7/site-packages/flask/app.py", line 2447, in wsgi_app
response = self.full_dispatch_request()
File "/PythonAPI/flask/env/lib/python3.7/site-packages/flask/app.py", line 1952, in full_dispatch_request
rv = self.handle_user_exception(e)
File "/PythonAPI/flask/env/lib/python3.7/site-packages/flask_restful/__init__.py", line 272, in error_router
return original_handler(e)
File "/PythonAPI/flask/env/lib/python3.7/site-packages/flask/app.py", line 1821, in handle_user_exception
reraise(exc_type, exc_value, tb)
File "/PythonAPI/flask/env/lib/python3.7/site-packages/flask/_compat.py", line 38, in reraise
raise value.with_traceback(tb)
File "/PythonAPI/flask/env/lib/python3.7/site-packages/flask/app.py", line 1950, in full_dispatch_request
rv = self.dispatch_request()
File "/PythonAPI/flask/env/lib/python3.7/site-packages/flask/app.py", line 1936, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)
File "/PythonAPI/flask/env/lib/python3.7/site-packages/flask_restful/__init__.py", line 472, in wrapper
return self.make_response(data, code, headers=headers)
File "/PythonAPI/flask/env/lib/python3.7/site-packages/flask_restful/__init__.py", line 501, in make_response
resp = self.representations[mediatype](data, *args, **kwargs)
File "/PythonAPI/flask/env/lib/python3.7/site-packages/flask_restful/representations/json.py", line 21, in output_json
dumped = dumps(data, **settings) + "\n"
File "/usr/local/Cellar/python/3.7.4_1/Frameworks/Python.framework/Versions/3.7/lib/python3.7/json/__init__.py", line 238, in dumps
**kw).encode(obj)
File "/usr/local/Cellar/python/3.7.4_1/Frameworks/Python.framework/Versions/3.7/lib/python3.7/json/encoder.py", line 201, in encode
chunks = list(chunks)
File "/usr/local/Cellar/python/3.7.4_1/Frameworks/Python.framework/Versions/3.7/lib/python3.7/json/encoder.py", line 438, in _iterencode
o = _default(o)
File "/usr/local/Cellar/python/3.7.4_1/Frameworks/Python.framework/Versions/3.7/lib/python3.7/json/encoder.py", line 179, in default
raise TypeError(f'Object of type {o.__class__.__name__} '
TypeError: Object of type bytes is not JSON serializable
什么时候
def post(self):
keys = []
wb = Workbook()
ws = wb.active
json_data = request.get_json()
for i in range(len(json_data)):
sub_obj = json_data[i]
if i == 0:
keys = list(sub_obj.keys())
for k in range(len(keys)):
# row or column index start from 1
ws.cell(row=(i + 1), column=(k + 1), value=keys[k]);
for j in range(len(keys)):
ws.cell(row=(i + 2), column=(j + 1), value=sub_obj[keys[j]]);
wb.save("test.xlsx")
工作正常。
有没有想过第一个示例中的 JSNO 数据会发生什么?
PS。我认为它必须与 Flask API 响应相关,因为默认响应是 JSON,但用它覆盖它
return output.getvalue(), 200, {'content-type': 'application/octet-stream'}
也不工作。
解决方案
通过更改默认的 Flask 响应类型标头来解决它,如下所示:
keys = []
wb = Workbook()
ws = wb.active
json_data = request.get_json()
with NamedTemporaryFile() as tmp:
for i in range(len(json_data)):
sub_obj = json_data[i]
if i == 0:
keys = list(sub_obj.keys())
for k in range(len(keys)):
# row or column index start from 1
ws.cell(row=(i + 1), column=(k + 1), value=keys[k]);
for j in range(len(keys)):
ws.cell(row=(i + 2), column=(j + 1), value=sub_obj[keys[j]]);
wb.save(tmp.name)
buf = BytesIO(tmp.read())
response = app.make_response(buf.getvalue())
response.headers['content-type'] = 'application/octet-stream'
return response
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