PyStreamPDF

Extract only what matters from PDFs, so you send less to LLMs.

Stop sending entire documents to LLMs. PyStreamPDF parses PDF structure and splits content into semantic, token-budget-aware chunks so you can send only the relevant parts of a document to a model. See "Token Savings" below for how much that saves in practice — it depends on your documents.

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30-Second Start

from pystreampdf import SemanticChunker, ElementType

with open("financial_report.pdf", "rb") as f:
    text = f.read().decode("latin-1", errors="ignore")  # or use a real PDF text extractor first

chunker = SemanticChunker(target_tokens=500)
chunks = chunker.chunk_content(
    text, element_type=ElementType.TEXT, page_start=1, page_end=1
)
print(f"Split into {len(chunks)} semantic chunks")

There is no Document/.extract_relevant() class in this package — SemanticChunker (shown above) and PDFCache (see "Quick Start: Document Extraction" below) are the real, exported API. If you built against a Document class from an earlier version of these docs, it never actually existed in source; see Known Issues.

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Why PyStreamPDF?

The Problem:

• You send entire PDFs to LLMs (wasteful, expensive)
• RAG systems retrieve too much content
• Token costs skyrocket on large documents
• No way to know which parts actually matter

The Solution:

• Semantic chunking with context awareness (real, in SemanticChunker)
• Token-budget-aware caching (real, in PDFCache / TokenBudgetConfig)
• Reduces the volume of text you send per query — see "Token Savings" below for what's measured vs. illustrative

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Key Features

• Real encryption/permission detection: Backed by PDFium's actual document security APIs — not a stub. Encrypted, password-protected, and permission-restricted PDFs are detected and reported accurately; opening with a wrong/missing password fails closed rather than silently succeeding.
• Honest failure signaling: If a PDF can't be parsed (corrupt, truncated, unsupported), you get a real error — never fabricated placeholder content.
• Intelligent Extraction: Find relevant sections automatically
• Semantic Chunking: Context-aware splitting, not just word count
• Multi-Format: Text, tables, images, charts, OCR
• Token Budgeting: Allocate tokens by document type
• Smart Caching: L1 memory + L2 disk (HMAC-signed on disk — no unverified deserialization)
• Metadata Preservation: Keep tables, images, structure
• Production-Ready: 557 passing tests (2 skipped when optional OCR system deps aren't installed)

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Real-World Use Cases

See examples/basic_parse.py for the Rust-backed pystreampdf.open() path (document/page/structure inspection — requires the compiled _core extension, see Known Issues) and examples/token_budget_and_cache_example.py for the pure-Python SemanticChunker + PDFCache + TokenBudgetConfig path shown above. Both are real, runnable scripts — copying them is more reliable than a README snippet for an evolving API.

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Token Savings

A note on how token counts are computed: by default, token counts use a len(text) / 4 heuristic (a common rule of thumb, but approximate — it can be off by a meaningful margin, especially for code or non-English text). Install the optional tiktoken extra for exact BPE token counts:

pip install "pystreampdf[tiktoken]"

When tiktoken is installed, pystreampdf.tokenizer.is_exact() returns True and counts use the real cl100k_base encoding; otherwise it falls back to the heuristic. Check pystreampdf.tokenizer.TOKENIZER_MODE to see which mode produced a given number.

Actual token savings depend entirely on your documents and how narrowly you scope extract_relevant-style queries — there's no committed benchmark result in this repo backing a specific percentage (the earlier "70%"/"10-50x" style claims in this README and in __init__.py's docstring weren't measured against anything checked in). Run examples/token_budget_and_cache_example.py against your own documents to get a real number for your use case.

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Security Notes

• Encryption & permissions: pystreampdf._core.PyPdfDocument.is_encrypted(), .permissions(), and .open_with_password() are backed by PDFium's real document security APIs. A wrong or missing password on an encrypted PDF raises an error — it never falls back to an unauthenticated parse.
• Cache integrity: the on-disk (L2) cache is HMAC-SHA256 signed using a key generated on first use and stored with owner-only (0600) permissions. A tampered or foreign cache file fails signature verification and is discarded before any deserialization occurs.
• MCP/DAB connector: binds to 127.0.0.1 with no cross-origin access and read-only permissions by default. Wider exposure requires an explicit allow_remote=True opt-in — review the security implications first, since the connector has no authentication of its own.

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Installation

pip install pystreampdf

# With exact token counting (tiktoken)
pip install "pystreampdf[tiktoken]"

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Documentation

• Quick Start — Process your first PDF
• Extraction Strategies — Different approaches for different documents
• Token Budgeting — Control context allocation
• Token Budget Multipliers — Comprehensive token budget guide with examples
• Examples — Real-world RAG optimization

Quick Start: Document Extraction

from pystreampdf import SemanticChunker, PDFCache, TokenBudgetConfig, BudgetRule

# Setup budget config
budget_config = TokenBudgetConfig(
    base_budget=800,
    rules=[BudgetRule("complex", 1.1, match_fields=["filename"])]
)

# Initialize cache with budget management
cache = PDFCache(
    memory_limit_mb=500,
    disk_cache_dir="./pdf_cache",
    token_budget_config=budget_config
)

# Process PDF with intelligent chunking
def extract_pdf(pdf_path):
    chunks, preview, title, pages = cache.get_or_process(
        pdf_path,
        process_fn=extract_chunks
    )
    return chunks

# Use semantic chunker directly
chunker = SemanticChunker(target_tokens=500)
chunks = chunker.chunk_content(text, element_type=ElementType.TEXT, page_start=1, page_end=1)

Budget Configuration

Default Settings

• Minimum budget: 500 tokens (fixed)
• Maximum budget: 1000 tokens (fixed)
• Default base: 1000 tokens
• Multiplier range: 0.5 - 1.5 (common)

Dynamic Adjustment via Multipliers

Use keyword-based rules to scale within the 500-1000 range without changing hard limits. See examples for financial, legal, and summary documents.

MCP Integration (optional, local by default)

PyStreamPDF ships an optional MCP/DAB connector (pystreampdf._mcp_connector) exposing document-processing tools (extract text/tables/images, OCR, structure detection, metadata, chunking, citations, validation). It's opt-in, binds to 127.0.0.1 only, and requires allow_remote=True to be exposed beyond localhost. See examples/mcp_pystreampdf.py.

Known Issues

• Earlier versions of this README documented a Document class with .extract_relevant() and a .token_savings attribute — verified against source: this class has never existed in this package. Fixed in this pass to describe the real, exported API (SemanticChunker, PDFCache, TokenBudgetConfig, and the Rust-backed pystreampdf.open()).
• The published PyPI wheel is the only wheel on PyPI — macOS arm64 only, no sdist. On any other platform or Python version, pip install will fail without a local Rust toolchain to build from source.
• The published version (2.2.1) is ahead of what's tagged in this repo's Cargo.toml/init.py (2.2.0) Resolved: 2.3.0 (this release) is unambiguously ahead of both 2.2.0 and 2.2.1.
• The Rust-backed pystreampdf.open() / pystreampdf.load_index() API (used in examples/basic_parse.py) silently becomes None if the compiled _core extension isn't available (e.g. a from-source install without maturin develop) — falling back to SemanticChunker/PDFCache in that case, per the code above, not a hard error.
• The "Tests & Build" GitHub Actions workflow was red for several weeks due to two CI infrastructure bugs (not the test suite itself), both now fixed and confirmed green in CI: run 32611116541. First, dtolnay/rust-toolchain@v1 required an explicit toolchain input the workflow didn't provide, failing both jobs before any tests ran — fixed by pinning to dtolnay/rust-toolchain@stable. Second, once that was fixed, maturin develop failed in the Python-test job because actions/setup-python doesn't provide an active virtualenv, which maturin requires — fixed by creating and activating a .venv before the build step. Actual CI output as of 2.2.0: pytest — 536 passed, 2 skipped (Python 3.10, 3.11, and 3.12, each identical); cargo test — 23 passed, 0 failed. (The Rust suite has 23 tests, not 536 — an earlier version of this section conflated the pytest count with the Rust one.) As of 2.3.0: pytest — 557 passed, 2 skipped (21 new tests added for tests/test_mcp_tools.py).

License

Proprietary License — Free to use with explicit attribution. See LICENSE.

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PyStreamPDF v2.3.0 | Intelligent PDF processing for AI | Python 3.9+ | 557 passing tests