No output when executing python file from c#

Question

I build a Webscraper in python, which generates the right output when executed. Now I wanted to implement it to a C# project and it doesn´t work. I just don´t get any ouput from it. I tried finding a problem with printin things to labels in different steps but it seems to work fine. My python code:

import bs4
import requests
from bs4 import BeautifulSoup

r = requests.get("https://fred.stlouisfed.org/series/AAA")
soup = bs4.BeautifulSoup(r.text,"lxml")
soup_find = soup.find_all("div",{"class":"pull-left meta-col"})[0].find("span",{"class":"series-meta-observation-value"}).text
print(soup_find)

And my C# Code (in Visual Studio):

        private void cmd_scrape_Click(object sender, EventArgs e)
    {
        string fileName = @"My\path\to\Webscraper.py";
        Process p = new Process();
        p.StartInfo = new ProcessStartInfo(@"My\path\to\python.exe", fileName)
        {
            RedirectStandardOutput = true,
            UseShellExecute = false,
            CreateNoWindow = true
        };
        p.Start();
        lbl_Out.Text = "Starting...";
        string Output = p.StandardOutput.ReadToEnd();
        lbl_Out.Text = "Waiting for exit...";
        p.WaitForExit();
        lbl_Out.Text = "Done";
        lbl_Out.Text = Output;
    }

Unfortunatly it didnt help, I tried to modify my code, but nothing — Marvlogs
– Marvlogs, Commented Jun 28, 2020 at 12:28
As an idea, try adding newline \r\n to python's output at the end of data. — aepot
– aepot, Commented Jun 28, 2020 at 14:19

aepot · Accepted Answer · 2020-06-30 16:47:34Z

2

I can't directly answer to your question because I have no python installed and can't reproduce the problem. But I'll show how to do the same thing completely with C#.

I assume that the C# project is WinForms.

Install 2 NuGet packages (in Visual Studio menu Project -> Manage Nuget Packages)

HtmlAgilityPack
Fizzler.Systems.HtmlAgilityPack

First one provides HTML parser, 2nd provides an extension HtmlNode.QuerySelector. Query syntax for QuerySelector is almost the same as in JavaScript.

After installation add namespaces to the code.

using HtmlAgilityPack;
using HtmlDocument = HtmlAgilityPack.HtmlDocument; // overrides class name conflict with System.Windows.Forms.HtmlDocument
using Fizzler.Systems.HtmlAgilityPack;

And whole code of the project

public partial class Form1 : Form
{
    private static readonly HttpClient client = new HttpClient();

    public Form1()
    {
        InitializeComponent();
    }

    private async void button1_Click(object sender, EventArgs e)
    {
        try
        {
            label1.Text = "Connecting";
            using (HttpResponseMessage response = await client.GetAsync("https://fred.stlouisfed.org/series/AAA", HttpCompletionOption.ResponseHeadersRead))
            {
                response.EnsureSuccessStatusCode();
                label1.Text = "Receiving data";
                string text = await response.Content.ReadAsStringAsync();
                HtmlDocument doc = new HtmlDocument();
                doc.LoadHtml(text);
                label1.Text = doc.DocumentNode.QuerySelector("div.pull-left.meta-col span.series-meta-observation-value").InnerText;
            }
        }
        catch (Exception ex)
        {
            label1.Text = "Error";
            MessageBox.Show(ex.Message + "\r\n\r\n" + ex.StackTrace);
        }
    }
}

edited Jun 30, 2020 at 16:47

answered Jun 28, 2020 at 13:37

aepot

4,8642 gold badges16 silver badges30 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Marvlogs Over a year ago

Thank you very much for the code, I hope you are fine with me using it for my application?

aepot Over a year ago

@Marvlogs You're welcome. Everything on StackOverflow is OK to use it for your application.

AnonymousKKYY · Accepted Answer · 2020-06-29 02:19:08Z

1

I tested the python and C# code, and it works fine and print "2.50". Maybe you can try to add break point to confirm whether the code in cmd_scrape_Click has been executed.

answered Jun 29, 2020 at 2:19

AnonymousKKYY

3,7754 gold badges15 silver badges40 bronze badges

1 Comment

Marvlogs Over a year ago

It has been executed, which I can see by removing the lbl_Out.Text=Output, because then it says "Done". There has to be something with the Output Text. I will keep trying, but thanks for the idea!

Collectives™ on Stack Overflow

No output when executing python file from c#

2 Answers 2

2 Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related