Python integration

The Aspire Python hosting integration lets you model Python scripts, modules, executables, and ASGI web apps as first-class resources in your AppHost project. Aspire manages virtual environment setup, injects connection strings and service URLs into the Python process, and wires up service discovery and observability automatically.

First-class Python support

As of Aspire 13, Python is a first-class workload with the Aspire.Hosting.Python package. The previous CommunityToolkit.Aspire.Hosting.Python.Extensions package is deprecated, and its functionality has been integrated into the official package with full support for debugging, service discovery, and deployment alongside .NET and JavaScript applications.

Hosting integration

Aspire CLI

Aspire CLI — Tilføj Aspire.Hosting.Python-pakke

aspire add python

Aspire CLI er interaktiv; vælg det passende søgeresultat når du bliver spurgt:

Aspire CLI — Eksempel output

Select an integration to add:

> python (Aspire.Hosting.Python)
> Other results listed as selectable options...

Note

Hvis der kun er ét resultat, vælges det automatisk. Du skal stadig bekræfte versionen.

apphost.cs (C# file-based app)

C# — AppHost.cs

#:package Aspire.Hosting.Python@*

PackageReference (*.csproj)

XML — Tilføj Aspire.Hosting.Python pakkereference

<PackageReference Include="Aspire.Hosting.Python" Version="*" />

Add Python app

Use AddPythonApp to run a Python script directly:

C#

C# — AppHost.cs

var builder = DistributedApplication.CreateBuilder(args);

var python = builder.AddPythonApp(
        name: "python-api",
        projectDirectory: "../python-app",
        scriptPath: "main.py")
    .WithHttpEndpoint(port: 8000, env: "PORT");

builder.AddProject<Projects.ExampleProject>("example")
    .WithReference(python);

builder.Build().Run();

TypeScript

apphost.ts

import { createBuilder } from "./.modules/aspire.js";

const builder = await createBuilder();

const python = await builder.addPythonApp("python-api", "../python-app", "main.py");
await python.withHttpEndpoint({ port: 8000, env: "PORT" });

const example = await builder.addProject("example", "../ExampleProject/ExampleProject.csproj");
await example.withReference(python);

await builder.build().run();

AddPythonApp / addPythonApp requires:

• name — the resource name shown in the Aspire dashboard
• projectDirectory / appDirectory — path to the directory containing your Python application
• scriptPath — the Python script to run, relative to the project directory

Add Python module

Use AddPythonModule to run a Python module (the equivalent of python -m <module>):

C#

C# — AppHost.cs

var builder = DistributedApplication.CreateBuilder(args);

var python = builder.AddPythonModule(
        name: "python-module",
        projectDirectory: "../python-app",
        moduleName: "mymodule")
    .WithHttpEndpoint(port: 8000, env: "PORT");

builder.Build().Run();

TypeScript

apphost.ts

import { createBuilder } from "./.modules/aspire.js";

const builder = await createBuilder();

const python = await builder.addPythonModule("python-module", "../python-app", "mymodule");
await python.withHttpEndpoint({ port: 8000, env: "PORT" });

await builder.build().run();

AddPythonModule / addPythonModule requires:

• name — the resource name shown in the Aspire dashboard
• projectDirectory / appDirectory — path to the directory containing your Python application
• moduleName — the Python module to run

Add Python executable

Use AddPythonExecutable to run a CLI tool installed in the virtual environment (for example, uvicorn or a custom script):

C#

C# — AppHost.cs

var builder = DistributedApplication.CreateBuilder(args);

var python = builder.AddPythonExecutable(
    name: "python-tool",
    projectDirectory: "../python-app",
    executable: "uvicorn",
    args: ["main:app", "--host", "0.0.0.0", "--port", "8000"]);

builder.Build().Run();

TypeScript

apphost.ts

import { createBuilder } from "./.modules/aspire.js";

const builder = await createBuilder();

// TypeScript: pass additional arguments via withArgs after creation
const python = await builder.addPythonExecutable("python-tool", "../python-app", "uvicorn");
await python.withArgs(["main:app", "--host", "0.0.0.0", "--port", "8000"]);

await builder.build().run();

Note

In the TypeScript AppHost, addPythonExecutable accepts only name, appDirectory, and executableName. Pass additional command-line arguments by chaining .withArgs(...) after the resource is created.

Add Uvicorn app

For ASGI web frameworks like FastAPI, Starlette, and Quart, use AddUvicornApp which pre-configures Uvicorn as the ASGI server:

C#

C# — AppHost.cs

var builder = DistributedApplication.CreateBuilder(args);

var python = builder.AddUvicornApp(
        name: "python-api",
        projectDirectory: "../python-app",
        appName: "main:app")
    .WithHttpEndpoint(port: 8000, env: "PORT");

builder.AddProject<Projects.ExampleProject>("example")
    .WithReference(python);

builder.Build().Run();

TypeScript

apphost.ts

import { createBuilder } from "./.modules/aspire.js";

const builder = await createBuilder();

const python = await builder.addUvicornApp("python-api", "../python-app", "main:app");
await python.withHttpEndpoint({ port: 8000, env: "PORT" });

const example = await builder.addProject("example", "../ExampleProject/ExampleProject.csproj");
await example.withReference(python);

await builder.build().run();

AddUvicornApp / addUvicornApp requires:

• name — the resource name shown in the Aspire dashboard
• projectDirectory / appDirectory — path to the directory containing your Python application
• appName / app — the ASGI application in module:variable format (for example, main:app for an app variable in main.py)

Uvicorn configuration

Configure Uvicorn worker count and log level through environment variables:

C#

C# — AppHost.cs

var builder = DistributedApplication.CreateBuilder(args);

var python = builder.AddUvicornApp("python-api", "../python-app", "main:app")
    .WithHttpEndpoint(port: 8000, env: "PORT")
    .WithEnvironment("UVICORN_WORKERS", "4")
    .WithEnvironment("UVICORN_LOG_LEVEL", "info");

builder.Build().Run();

TypeScript

apphost.ts

import { createBuilder } from "./.modules/aspire.js";

const builder = await createBuilder();

const python = await builder.addUvicornApp("python-api", "../python-app", "main:app");
await python.withHttpEndpoint({ port: 8000, env: "PORT" });
await python.withEnvironment("UVICORN_WORKERS", "4");
await python.withEnvironment("UVICORN_LOG_LEVEL", "info");

await builder.build().run();

Common Uvicorn environment variables:

• UVICORN_PORT — port to listen on
• UVICORN_HOST — host to bind to (default: 127.0.0.1)
• UVICORN_WORKERS — number of worker processes
• UVICORN_LOG_LEVEL — logging level (debug, info, warning, error)

Virtual environment management

The Python hosting integration automatically detects and uses a virtual environment in the project directory. By default, if a requirements.txt or pyproject.toml is found, Aspire creates and activates a virtual environment before starting the app.

Custom virtual environment

To specify a custom virtual environment path, use WithVirtualEnvironment:

C#

C# — AppHost.cs

var builder = DistributedApplication.CreateBuilder(args);

var python = builder.AddPythonApp("python-api", "../python-app", "main.py")
    .WithVirtualEnvironment("../python-app/.venv");

builder.Build().Run();

TypeScript

apphost.ts

import { createBuilder } from "./.modules/aspire.js";

const builder = await createBuilder();

const python = await builder.addPythonApp("python-api", "../python-app", "main.py");
await python.withVirtualEnvironment("../python-app/.venv");

await builder.build().run();

Disable virtual environment

To opt out of automatic virtual environment management, call WithoutVirtualEnvironment in C#:

C# — AppHost.cs

var builder = DistributedApplication.CreateBuilder(args);

var python = builder.AddPythonApp("python-api", "../python-app", "main.py")
    .WithoutVirtualEnvironment();

builder.Build().Run();

Note

WithoutVirtualEnvironment is not yet available in the TypeScript AppHost. To achieve the same effect from a TypeScript AppHost, omit withVirtualEnvironment and ensure the Python executable is on PATH.

Package management

uv package manager

Use WithUv to opt into the uv package manager, which installs dependencies significantly faster than pip:

C#

C# — AppHost.cs

var builder = DistributedApplication.CreateBuilder(args);

var python = builder.AddUvicornApp("python-api", "../python-app", "main:app")
    .WithUv()
    .WithHttpEndpoint(port: 8000, env: "PORT");

builder.Build().Run();

TypeScript

apphost.ts

import { createBuilder } from "./.modules/aspire.js";

const builder = await createBuilder();

const python = await builder.addUvicornApp("python-api", "../python-app", "main:app");
await python.withUv();
await python.withHttpEndpoint({ port: 8000, env: "PORT" });

await builder.build().run();

pip package manager

Use WithPip to explicitly select pip:

C#

C# — AppHost.cs

var builder = DistributedApplication.CreateBuilder(args);

var python = builder.AddPythonApp("python-api", "../python-app", "main.py")
    .WithPip()
    .WithHttpEndpoint(port: 8000, env: "PORT");

builder.Build().Run();

TypeScript

apphost.ts

import { createBuilder } from "./.modules/aspire.js";

const builder = await createBuilder();

const python = await builder.addPythonApp("python-api", "../python-app", "main.py");
await python.withPip();
await python.withHttpEndpoint({ port: 8000, env: "PORT" });

await builder.build().run();

Tip

If neither WithUv nor WithPip is specified, Aspire automatically selects the package manager based on project files (pyproject.toml → uv, requirements.txt → pip).

Configure endpoints

Python apps typically read the port from an environment variable. Use WithHttpEndpoint to declare the port and inject the variable name:

C#

C# — AppHost.cs

var builder = DistributedApplication.CreateBuilder(args);

var python = builder.AddUvicornApp("python-api", "../python-app", "main:app")
    .WithHttpEndpoint(port: 8000, env: "PORT");

builder.Build().Run();

TypeScript

apphost.ts

import { createBuilder } from "./.modules/aspire.js";

const builder = await createBuilder();

const python = await builder.addUvicornApp("python-api", "../python-app", "main:app");
await python.withHttpEndpoint({ port: 8000, env: "PORT" });

await builder.build().run();

Multiple endpoints

A Python app can expose more than one endpoint:

C#

C# — AppHost.cs

var builder = DistributedApplication.CreateBuilder(args);

var python = builder.AddPythonApp("python-api", "../python-app", "main.py")
    .WithHttpEndpoint(port: 8000, env: "HTTP_PORT", name: "http")
    .WithHttpEndpoint(port: 8443, env: "HTTPS_PORT", name: "https");

builder.Build().Run();

TypeScript

apphost.ts

import { createBuilder } from "./.modules/aspire.js";

const builder = await createBuilder();

const python = await builder.addPythonApp("python-api", "../python-app", "main.py");
await python.withHttpEndpoint({ port: 8000, env: "HTTP_PORT", name: "http" });
await python.withHttpEndpoint({ port: 8443, env: "HTTPS_PORT", name: "https" });

await builder.build().run();

Health checks

Declare an HTTP health-check endpoint so Aspire knows when the app is ready:

C#

C# — AppHost.cs

var builder = DistributedApplication.CreateBuilder(args);

var python = builder.AddUvicornApp("python-api", "../python-app", "main:app")
    .WithHttpEndpoint(port: 8000, env: "PORT")
    .WithHttpHealthCheck("/health");

builder.Build().Run();

TypeScript

apphost.ts

import { createBuilder } from "./.modules/aspire.js";

const builder = await createBuilder();

const python = await builder.addUvicornApp("python-api", "../python-app", "main:app");
await python.withHttpEndpoint({ port: 8000, env: "PORT" });
await python.withHttpHealthCheck("/health");

await builder.build().run();

Environment variables

Inject arbitrary environment variables with WithEnvironment:

C#

C# — AppHost.cs

var builder = DistributedApplication.CreateBuilder(args);

var python = builder.AddPythonApp("python-api", "../python-app", "main.py")
    .WithEnvironment("DEBUG", "true")
    .WithEnvironment("LOG_LEVEL", "debug");

builder.Build().Run();

TypeScript

apphost.ts

import { createBuilder } from "./.modules/aspire.js";

const builder = await createBuilder();

const python = await builder.addPythonApp("python-api", "../python-app", "main.py");
await python.withEnvironment("DEBUG", "true");
await python.withEnvironment("LOG_LEVEL", "debug");

await builder.build().run();

Service discovery

Reference other Aspire resources from a Python app using WithReference. Aspire injects the connection string as the ConnectionStrings__<resourcename> environment variable in the Python process:

C#

C# — AppHost.cs

var builder = DistributedApplication.CreateBuilder(args);

var db = builder.AddPostgres("postgres")
    .AddDatabase("mydb");

var python = builder.AddPythonApp("python-api", "../python-app", "main.py")
    .WithReference(db);

builder.Build().Run();

TypeScript

apphost.ts

import { createBuilder } from "./.modules/aspire.js";

const builder = await createBuilder();

const postgres = await builder.addPostgres("postgres");
const db = await postgres.addDatabase("mydb");

const python = await builder.addPythonApp("python-api", "../python-app", "main.py");
await python.withReference(db);

await builder.build().run();

Read the connection string in Python using the ConnectionStrings__mydb environment variable (double-underscore separator for Python/shell environments):

Python — main.py

import os

connection_string = os.environ.get("ConnectionStrings__mydb")

HTTPS configuration

By default, Python apps run over HTTP in local development. To enable HTTPS, use WithHttpsEndpoint together with WithHttpsDeveloperCertificate:

C#

C# — AppHost.cs

var builder = DistributedApplication.CreateBuilder(args);

var python = builder.AddUvicornApp("python-api", "../python-app", "main:app")
    .WithHttpsEndpoint(port: 8443, env: "PORT")
    .WithHttpsDeveloperCertificate();

builder.Build().Run();

TypeScript

apphost.ts

import { createBuilder } from "./.modules/aspire.js";

const builder = await createBuilder();

const python = await builder.addUvicornApp("python-api", "../python-app", "main:app");
await python.withHttpsEndpoint({ port: 8443, env: "PORT" });
await python.withHttpsDeveloperCertificate();

await builder.build().run();

WithHttpsDeveloperCertificate exports the ASP.NET Core development certificate and injects it into the Python process as environment variables. Read those variables in your Uvicorn startup:

Python — main.py

import os
import uvicorn

if __name__ == "__main__":
    ssl_keyfile = os.environ.get("ASPNETCORE_Kestrel__Certificates__Default__KeyPath")
    ssl_certfile = os.environ.get("ASPNETCORE_Kestrel__Certificates__Default__Path")

    uvicorn.run(
        "main:app",
        host="0.0.0.0",
        port=int(os.environ.get("PORT", 8443)),
        ssl_keyfile=ssl_keyfile,
        ssl_certfile=ssl_certfile,
    )

Note

HTTPS is needed primarily when your Python service is exposed externally. For internal service-to-service communication within an Aspire app, HTTP is sufficient.

Internal versus external service exposure

By default, Aspire services are only accessible within the distributed application. Use WithExternalHttpEndpoints to expose a service to external traffic:

C#

C# — AppHost.cs

var builder = DistributedApplication.CreateBuilder(args);

var internalApi = builder.AddUvicornApp("internal-api", "../internal-api", "main:app")
    .WithHttpEndpoint(port: 8001, env: "PORT");
// internalApi is NOT exposed publicly — only reachable by other Aspire resources

var publicApi = builder.AddUvicornApp("public-api", "../public-api", "main:app")
    .WithHttpEndpoint(port: 8000, env: "PORT")
    .WithExternalHttpEndpoints();
// publicApi IS exposed publicly

builder.AddProject<Projects.WebFrontend>("frontend")
    .WithReference(internalApi)
    .WithReference(publicApi);

builder.Build().Run();

TypeScript

apphost.ts

import { createBuilder } from "./.modules/aspire.js";

const builder = await createBuilder();

const internalApi = await builder.addUvicornApp("internal-api", "../internal-api", "main:app");
await internalApi.withHttpEndpoint({ port: 8001, env: "PORT" });
// internalApi is NOT exposed publicly — only reachable by other Aspire resources

const publicApi = await builder.addUvicornApp("public-api", "../public-api", "main:app");
await publicApi.withHttpEndpoint({ port: 8000, env: "PORT" });
await publicApi.withExternalHttpEndpoints();
// publicApi IS exposed publicly

const frontend = await builder.addProject("frontend", "../WebFrontend/WebFrontend.csproj");
await frontend.withReference(internalApi);
await frontend.withReference(publicApi);

await builder.build().run();

Tip

Keep backend Python services (databases, AI inference, internal APIs) unexposed. Only expose services that browsers or external clients need to reach directly.

Debugging

The Python hosting integration provides full debugging support in Visual Studio Code:

1. Install the Aspire VS Code extension
2. Set breakpoints in your Python code
3. Run the Aspire app host
4. The debugger automatically attaches to your Python application

Tip

The Aspire VS Code extension automatically generates launch configurations for Python applications in your Aspire solution, enabling zero-configuration debugging.

Deployment

When deploying your Aspire application, the Python hosting integration automatically generates production-ready Dockerfiles for your Python services:

# Auto-generated Dockerfile
FROM python:3.12-slim

WORKDIR /app
COPY requirements.txt .
RUN pip install -r requirements.txt

COPY . .
CMD ["python", "main.py"]

Note

The generated Dockerfile is tailored to your detected Python version and dependency configuration.

See also

• 📦 Aspire.Hosting.Python NuGet package
• Python language reference
• Uvicorn documentation
• uv package manager documentation
• FastAPI documentation
• Aspire integrations overview
• Build your first Aspire app
• Deploy your first Aspire app
• Aspire GitHub repository