Python Flask 应用程序在本地运行，但在 Heroku 上托管时返回 AttributeError

我正在开发大学申请。 该 Web 应用程序使用 joblib 加载给定模型，并且为了工作，它使用了 FlexibleScaler 类：

灵活.py

from sklearn.preprocessing import MinMaxScaler, StandardScaler, PowerTransformer, MaxAbsScaler, RobustScaler, Normalizer
from sklearn.base import BaseEstimator, TransformerMixin

class FlexibleScaler(BaseEstimator, TransformerMixin):
    def __init__(self, scaler=None):
        self.scaler = scaler
        self.check = False


    def __assign_scaler(self):
        if self.scaler == 'min-max':
            self.method = MinMaxScaler()
        elif self.scaler == 'standard':
            self.method = StandardScaler()
        elif self.scaler == 'yeo-johnson':
            self.method = PowerTransformer(method='yeo-johnson')
        elif self.scaler == 'box-cox':
            self.method = PowerTransformer(method='box-cox')
        elif self.scaler == 'max-abs':
            self.method = MaxAbsScaler()
        elif self.scaler == 'robust':
            self.method = RobustScaler()
        elif self.scaler == 'normalize':
            self.method = Normalizer()
        else:
            self.method = None
        self.check = True

    def fit_transform(self, X, y=None, **fit_params):
        if not self.check:
            self.__assign_scaler()
        if self.method is None:
            return X
        return self.method.fit_transform(X, y, **fit_params)

    def fit(self, X):
        if not self.check:
            self.__assign_scaler()
        if self.method is None:
            return X
        self.method.fit(X)

    def transform(self, X):
        if not self.check:
            self.__assign_scaler()
        if self.method is None:
            return X
        return self.method.transform(X)

烧瓶启动.py

from flask import Flask, Response, render_template, request, flash, redirect, session, g
import joblib
import pandas as pd
import numpy as np
from sklearn import datasets
from sklearn.ensemble import RandomForestClassifier
from sklearn.preprocessing import MinMaxScaler, StandardScaler, PowerTransformer, MaxAbsScaler, RobustScaler, Normalizer
from sklearn.base import BaseEstimator, TransformerMixin
from flexible import FlexibleScaler


UPLOAD_FOLDER = '/tmp/'
ALLOWED_EXTENSIONS = {'csv'}
app = Flask(__name__)

app.config['UPLOAD_FOLDER'] = UPLOAD_FOLDER
app.config['ALLOWED_EXTENSIONS'] = ALLOWED_EXTENSIONS


@app.route("/", methods=["POST", "GET"])
def home():

    if request.method == 'POST':

        //get data to process

        clf = joblib.load('ENS_fitted.joblib')

        prediction = clf.predict(features)
        pred_prob = clf.predict_proba(features)

        //do operations and return template

if __name__ == "__main__":
    app.run(debug = True)

这一切都在本地运行。当我在 Heroku 上部署时，我在 joblib.load() 上收到以下错误：

Traceback (most recent call last):

2020-09-24T21:27:30.117559+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.8/site-packages/flask/app.py", line 2447, in wsgi_app

2020-09-24T21:27:30.117559+00:00 app[web.1]:     response = self.full_dispatch_request()

2020-09-24T21:27:30.117560+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.8/site-packages/flask/app.py", line 1952, in full_dispatch_request

2020-09-24T21:27:30.117560+00:00 app[web.1]:     rv = self.handle_user_exception(e)

2020-09-24T21:27:30.117561+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.8/site-packages/flask/app.py", line 1821, in handle_user_exception

2020-09-24T21:27:30.117561+00:00 app[web.1]:     reraise(exc_type, exc_value, tb)

2020-09-24T21:27:30.117561+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.8/site-packages/flask/_compat.py", line 39, in reraise

2020-09-24T21:27:30.117562+00:00 app[web.1]:     raise value

2020-09-24T21:27:30.117563+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.8/site-packages/flask/app.py", line 1950, in full_dispatch_request

2020-09-24T21:27:30.117563+00:00 app[web.1]:     rv = self.dispatch_request()

2020-09-24T21:27:30.117563+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.8/site-packages/flask/app.py", line 1936, in dispatch_request

2020-09-24T21:27:30.117564+00:00 app[web.1]:     return self.view_functions[rule.endpoint](**req.view_args)

2020-09-24T21:27:30.117564+00:00 app[web.1]:   File "/app/flask_start.py", line 138, in home

2020-09-24T21:27:30.117564+00:00 app[web.1]:     clf = joblib.load('ENS_fitted.joblib')

2020-09-24T21:27:30.117565+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.8/site-packages/joblib/numpy_pickle.py", line 585, in load

2020-09-24T21:27:30.117565+00:00 app[web.1]:     obj = _unpickle(fobj, filename, mmap_mode)

2020-09-24T21:27:30.117566+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.8/site-packages/joblib/numpy_pickle.py", line 504, in _unpickle

2020-09-24T21:27:30.117566+00:00 app[web.1]:     obj = unpickler.load()

2020-09-24T21:27:30.117567+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.8/pickle.py", line 1210, in load

2020-09-24T21:27:30.117570+00:00 app[web.1]:     dispatch[key[0]](self)

2020-09-24T21:27:30.117570+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.8/pickle.py", line 1526, in load_global

2020-09-24T21:27:30.117570+00:00 app[web.1]:     klass = self.find_class(module, name)

2020-09-24T21:27:30.117571+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.8/pickle.py", line 1581, in find_class

2020-09-24T21:27:30.117571+00:00 app[web.1]:     return getattr(sys.modules[module], name)

AttributeError: module '__main__' has no attribute 'FlexibleScaler'

我不明白为什么会发生这种情况。导入就在那里并且在本地工作。 我尝试将FlexibleScaler类直接复制到flask_start.py中（它也可以在本地运行），但没有成功。

local 和 Heroku 之间唯一的变化是，在 Heroku 上我使用 Gunicorn 来启动应用程序。

请提供任何帮助，我们将不胜感激。

看来joblib.save()产生的ENS_fitted.joblib发生在flask_start.py直接从 python 运行。当这种情况发生时，flask_start将有一个__name__ of "__main__"。那么，当joblib.save()pickles，它将把FlexibleScaler实例保存为__main__.FlexibleScaler.

但是当你在gunicorn下部署并运行时，flask_start将有一个__name__ of "flask_start"。这令人困惑joblib.load()，它期望找到一个__main__.FlexibleScaler，然后放弃，如上面所示。

解决方案是重新生成保存的模型，但这次通过调用flask_start via

% FLASK_APP=flask_start flask run

then joblib.save()再次，然后重新部署。

Updated

如果你绝对无法重新生成模型，你可以尝试这个技巧。进口后在flask_start.py, add

import __main__
__main__.FlexibleScalar = FlexibleScalar

你可以joblib.load()模型，否则您将在另一个类中遇到类似的错误，在这种情况下，请重复此技巧。