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The requirements class variable in your fal App specifies which Python packages to install. It supports standard pip syntax, including version specifiers, wheel URLs, and private package indexes.

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Basic Requirements

Specify packages with version pinning for reproducible builds: 
class MyApp(fal.App):
    requirements = [
        "torch==2.5.0",
        "transformers==4.51.3",
        "diffusers==0.31.0",
        "accelerate==1.6.0",
    ]
Always pin your package versions to ensure reproducible builds across deployments.

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Using Prebuilt Wheels

You can install packages directly from wheel URLs. This is useful for custom-built packages or packages not available on PyPI.

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Direct URL

Provide the full URL to a wheel file: 
requirements = [
    "https://your-storage.example.com/wheels/mypackage-1.0.0-cp311-cp311-linux_x86_64.whl",
]

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Package @ URL (PEP 440)

Use the package@url syntax to give the package a name for dependency resolution: 
requirements = [
    "mypackage@https://your-storage.example.com/wheels/mypackage-1.0.0-cp311-cp311-linux_x86_64.whl",
]
This syntax is recommended when other packages depend on mypackage, as pip can properly track the dependency.

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Alternative Package Indexes

Use --extra-index-url or --find-links to install packages from alternative sources.

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Extra Index URL

Install packages from an additional PyPI-compatible index: 
requirements = [
    "torch==2.5.0",
    "--extra-index-url",
    "https://download.pytorch.org/whl/cu124",
]
The --extra-index-url flag must appear before any packages that need it. Place index flags at the beginning or directly before the relevant packages.
Use --find-links to search for packages in a directory or URL containing wheel files: 
requirements = [
    "mypackage",
    "--find-links",
    "https://github.com/your-org/releases/download/v1.0.0/",
]

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Multiple Indexes

Combine multiple index sources when needed: 
requirements = [
    "--extra-index-url",
    "https://download.pytorch.org/whl/cu124",
    "--extra-index-url",
    "https://your-company.example.com/simple",
    "torch==2.5.0",
    "your-internal-package==1.0.0",
]

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Private Packages

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Private Git Repositories

Install directly from a private GitHub repository using a personal access token: 
requirements = [
    "git+https://[email protected]/your-org/private-repo.git",
]
Pin to a specific commit or tag for reproducibility: 
requirements = [
    "git+https://[email protected]/your-org/[email protected]",
    "git+https://[email protected]/your-org/private-repo.git@abc123def",
]
Security Consideration: Tokens embedded in requirements are visible in your code. For better security:
  • Use short-lived tokens when possible
  • Consider hosting wheels on a storage service with pre-signed URLs
  • Use fal secrets for sensitive values in your app code

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Private PyPI Index

Install from a private PyPI server with authentication: 
requirements = [
    "--extra-index-url",
    "https://username:[email protected]/simple",
    "your-private-package==1.0.0",
]

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Pre-signed URLs

For private storage (S3, GCS, etc.), generate a pre-signed URL with an expiration time: 
requirements = [
    "https://your-bucket.s3.amazonaws.com/wheels/mypackage-1.0.0.whl?AWSAccessKeyId=...&Signature=...&Expires=...",
]

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Dynamic Wheel Selection

When you need different wheels for different Python versions or platforms, use a helper function: 
def get_package_wheel():
    import sys
    wheels = {
        10: "https://example.com/wheels/mypackage-1.0.0-cp310-cp310-linux_x86_64.whl",
        11: "https://example.com/wheels/mypackage-1.0.0-cp311-cp311-linux_x86_64.whl",
    }
    return wheels[sys.version_info.minor]


class MyApp(fal.App):
    machine_type = "GPU"
    requirements = [
        "torch==2.5.0",
        get_package_wheel(),
    ]
Helper functions are evaluated at deploy time on your local machine, so they have access to local environment variables and can make decisions based on the target Python version.