PDF Calendar Parsing Skill

Overview

This skill covers extracting calendar events and time blocks from PDF calendar documents using pdfplumber, a Python library for extracting text and tables from PDF files.

Installation

pip install pdfplumber

Key Concepts

How pdfplumber Works

• Opens PDF files and extracts text with position information
• Can identify text bounding boxes (x0, y0, x1, y1 coordinates)
• Supports extracting tables and structured data

Calendar Grid Extraction

For a calendar with hourly/time-based layout:

1. Extract all text from the PDF with position data
2. Identify time labels (hours on the left axis)
3. Identify event blocks by text content and bounding boxes
4. Calculate event duration by comparing Y-coordinates

Code Examples

Basic PDF Opening

import pdfplumber

with pdfplumber.open('/root/calendar.pdf') as pdf:
    page = pdf.pages[0]
    text = page.extract_text()
    print(text)

Extracting Text with Positions

import pdfplumber

with pdfplumber.open('/root/calendar.pdf') as pdf:
    page = pdf.pages[0]

    # Get all text objects with their positions
    for char in page.chars:
        print(f"Text: {char['text']}, X: {char['x0']}, Y: {char['y0']}")

Identifying Calendar Events

import pdfplumber

def extract_calendar_events(pdf_path):
    with pdfplumber.open(pdf_path) as pdf:
        page = pdf.pages[0]

        # Get all text with positions
        text_data = page.extract_text_with_layout()

        # Extract words and their bounding boxes
        words = page.extract_words()

        events = []
        for word in words:
            # word contains: 'text', 'x0', 'y0', 'x1', 'y1', 'size', 'font'
            if word['text'] not in ['12am', '1am', '2am']:  # Skip time labels
                events.append({
                    'text': word['text'],
                    'x0': word['x0'],
                    'y0': word['y0'],
                    'x1': word['x1'],
                    'y1': word['y1']
                })

        return events

Time Extraction from Layout

def extract_time_labels(page):
    """Extract hour labels from calendar time axis"""
    words = page.extract_words()
    time_labels = {}

    for word in words:
        text = word['text']
        # Match patterns like "10am", "2pm", "12am"
        if any(text.endswith(suffix) for suffix in ['am', 'pm']):
            y_position = word['y0']  # Vertical position
            time_labels[text] = y_position

    return sorted(time_labels.items(), key=lambda x: x[1])

Calculating Block Duration

def get_block_duration(y_start, y_end, time_lines, interval_minutes=15):
    """
    Calculate duration of a calendar block

    time_lines: list of (time_string, y_position) tuples, sorted by y
    interval_minutes: minutes between adjacent horizontal lines
    """
    # Find which time lines bracket this block
    start_time = None
    end_time = None

    for i, (time_str, y_pos) in enumerate(time_lines):
        if y_pos <= y_start and (i+1 >= len(time_lines) or time_lines[i+1][1] > y_start):
            start_time = time_str
        if y_pos <= y_end and (i+1 >= len(time_lines) or time_lines[i+1][1] >= y_end):
            end_time = time_str

    return start_time, end_time

Common Pitfalls

• Y-coordinates increase downward in PDFs (unlike normal coordinate systems)
• Text extraction might include artifacts or formatting characters
• Font sizes and positions can vary; use threshold matching
• Event blocks may have overlapping text; use grouping strategies

Best Practices

1. Always verify extracted text against visual inspection
2. Sort time labels by Y-coordinate to create accurate mapping
3. Use relative positioning (Y-coordinates) to determine time ranges
4. Store both start and end times for accuracy
5. Validate extracted times are within expected calendar hours