alexei-led/parsing-documents

Parsing Documents (PDF Extraction)

Extract structured information from PDF documents. Try the cheapest reliable method first.

Parsing Strategy (Priority Order)

1. Native Reading (primary)

Use the Read tool directly — it handles PDFs natively, including scanned/image PDFs:

Read → /path/to/document.pdf

2. CLI Tools (quick operations)

pdftotext document.pdf output.txt        # Extract text
pdftotext -layout document.pdf -         # Preserve layout
pdfinfo document.pdf                     # PDF metadata
pdftoppm -png document.pdf output        # Convert pages to images

3. Python Libraries (complex extraction)

pdfplumber — best for tables:

import pdfplumber

with pdfplumber.open("document.pdf") as pdf:
    for page in pdf.pages:
        tables = page.extract_tables()
        text = page.extract_text()

pypdf — metadata and forms:

from pypdf import PdfReader

reader = PdfReader("document.pdf")
metadata = reader.metadata
fields = reader.get_form_text_fields()

Common Extraction Patterns

Tables

def extract_tables(pdf_path):
    tables = []
    with pdfplumber.open(pdf_path) as pdf:
        for page_num, page in enumerate(pdf.pages, 1):
            for table in page.extract_tables():
                tables.append({"page": page_num, "data": table})
    return tables

Region by Bounding Box

def extract_region(pdf_path, page_num, bbox):
    with pdfplumber.open(pdf_path) as pdf:
        page = pdf.pages[page_num]
        return page.crop(bbox).extract_text()  # bbox = (x0, top, x1, bottom)

Field Extraction (e.g. invoices)

import re

patterns = {
    "invoice_number": r"Invoice\s*#?\s*(\d+)",
    "date": r"Date:\s*([\d/\-]+)",
    "total": r"Total:\s*\$?([\d,]+\.?\d*)",
}
data = {
    key: (m.group(1) if (m := re.search(p, text, re.IGNORECASE)) else None)
    for key, p in patterns.items()
}

Output Formats

JSON for structured extraction:

output = {
    "metadata": {"title": "...", "pages": 5},
    "pages": [{"page_number": 1, "text": "...", "tables": [...]}],
}

CSV for table data: csv.writer(f).writerows(table).

Workflow

1. Read natively with the Read tool
2. Assess structure: tables? forms? pure text?
3. Choose tool: simple text → pdftotext; tables → pdfplumber; forms → pypdf
4. Extract and validate the data
5. Format output (JSON, CSV, or Markdown)

Failure Handling

• Encrypted PDF: check with pdfinfo; may need a password — ask the user, do not guess
• Scanned/image PDF: use native reading rather than pdftotext
• Garbled text: try a different extraction method before reporting
• Missing tables: adjust pdfplumber table settings

table_settings = {"vertical_strategy": "lines", "horizontal_strategy": "lines"}
tables = page.extract_tables(table_settings)

If content cannot be reliably extracted (scanned images, encryption), report the failure explicitly rather than inventing values. If the task would require changes beyond extraction, stop and ask.