如何解决类型错误:在python flask api中，视图函数未返回有效响应

Question

我正在尝试从mongoDB数据库中检索数据，并尝试将该响应传递给前端reactjs应用程序。

但是我得到了这个错误，我不知道为什么会这样:

TypeError:视图函数未返回有效响应。返回类型必须是字符串、dict、元组、响应实例或WSGI可调用，但它是列表

我需要的是：

我需要检索所有mongodb文档并将其传递到前端应用程序中，以便我可以使用reactjs映射它以显示在表中。

这就是我正在尝试的，这给了我一个错误：

@app.route("/bemployees", methods=["GET"])
def retrieve_all_documents():
    client = pymongo.MongoClient(
        "<url>"
    )

    # database
    db = client.cdap

    # collection (table)
    collection = db.predicted_values

    documents_ = []

    for b in collection.find():

        documents_.append({'Age' :b['Age'] ,'DailyRate': b['DailyRate'],
                   'DistanceFromHome': b['DistanceFromHome'] , 'EnvironmentSatisfaction': b['EnvironmentSatisfaction'],
                   'HourlyRate':b['HourlyRate'],'JobInvolvement': b['JobInvolvement'],
                   'JobLevel': b['JobLevel'],'JobSatisfaction' :b['JobSatisfaction'],
                   'MonthlyIncome': b['MonthlyIncome'], 'MonthlyRate' :b['MonthlyRate'],
                   'NumCompaniesWorked': b['NumCompaniesWorked'],'PercentSalaryHike' :b['PercentSalaryHike'],
                   'RelationshipSatisfaction': b['RelationshipSatisfaction'],'StandardHours' :b['StandardHours'],
                   'TotalWorkingYears': b['TotalWorkingYears'],'TrainingTimesLastYear' :b['TrainingTimesLastYear'],
                   'YearsAtCompany': b['YearsAtCompany'],'YearsInCurrentRole' :b['YearsInCurrentRole'],
                   'YearsSinceLastPromotion': b['YearsSinceLastPromotion'],'YearsWithCurrManager' :b['YearsWithCurrManager'],
                   'MaritalStatus_': b['MaritalStatus_'],'JobRole_' :b['JobRole_'],
                   'Gender_': b['Gender_'],'EducationField_' :b['EducationField_'],
                   'Department_': b['Department_'],'BusinessTravel_' :b['BusinessTravel_'],
                   'OverTime_': b['OverTime_'],'Over18_' :b['Over18_'],
                   'empName': b['empName'],'empID' :b['empID'],
                   'PerformanceScore': b['PerformanceScore'],
                   'id': str(b['_id']) })

    return documents_ 

有人能帮我解决这个问题吗？

Answer 1

Flask视图无法返回列表。处理此问题的一种方法是将列表转换为JSON字符串：

import json
from flask import Response

@app.route("/bemployees", methods=["GET"])
def retrieve_all_documents():
    client = pymongo.MongoClient(
        "<url>"
    )

    # database
    db = client.cdap

    # collection (table)
    collection = db.predicted_values

    documents_ = []

    for b in collection.find():

        documents_.append({'Age' :b['Age'] ,'DailyRate': b['DailyRate'],
                   'DistanceFromHome': b['DistanceFromHome'] , 'EnvironmentSatisfaction': b['EnvironmentSatisfaction'],
                   'HourlyRate':b['HourlyRate'],'JobInvolvement': b['JobInvolvement'],
                   'JobLevel': b['JobLevel'],'JobSatisfaction' :b['JobSatisfaction'],
                   'MonthlyIncome': b['MonthlyIncome'], 'MonthlyRate' :b['MonthlyRate'],
                   'NumCompaniesWorked': b['NumCompaniesWorked'],'PercentSalaryHike' :b['PercentSalaryHike'],
                   'RelationshipSatisfaction': b['RelationshipSatisfaction'],'StandardHours' :b['StandardHours'],
                   'TotalWorkingYears': b['TotalWorkingYears'],'TrainingTimesLastYear' :b['TrainingTimesLastYear'],
                   'YearsAtCompany': b['YearsAtCompany'],'YearsInCurrentRole' :b['YearsInCurrentRole'],
                   'YearsSinceLastPromotion': b['YearsSinceLastPromotion'],'YearsWithCurrManager' :b['YearsWithCurrManager'],
                   'MaritalStatus_': b['MaritalStatus_'],'JobRole_' :b['JobRole_'],
                   'Gender_': b['Gender_'],'EducationField_' :b['EducationField_'],
                   'Department_': b['Department_'],'BusinessTravel_' :b['BusinessTravel_'],
                   'OverTime_': b['OverTime_'],'Over18_' :b['Over18_'],
                   'empName': b['empName'],'empID' :b['empID'],
                   'PerformanceScore': b['PerformanceScore'],
                   'id': str(b['_id']) })

    return Response(json.dumps(documents_), mimetype='application/json')