pdf_field_values.py

"""
This script writes simplified representations of a PDF file's fields in a text
file.

Args:
	1: the path to a PDF file
	2: (optional) the path to the output .txt file
"""


from path_arg_checks import check_io_path_pair
from pathlib import Path
from PyPDF2 import PdfFileReader
from sys import argv, exit


class PdfField:
	"""
	This class is a simplified representation of a PDF file field. It contains
	the field's name, type and value. The string representation matches the
	format "<name> (<type>): <value>".
	"""

	def __init__(self, name, type, value):
		"""
		The constructor needs the field's name, type and value. name and type
		can be instances of str or one of its subclasses. value can be an
		instance of any class.

		Args:
			name (str): the field's name
			type (str): the field's type
			value: the field's value
		"""
		self._name = name
		self._type = type
		self._value = value

	def __str__(self):
		return self._name + " (" + self._type + "): " + str(self._value)

	@property
	def name(self):
		"""
		str: the name of this PDF field
		"""
		return self._name

	@property
	def type(self):
		"""
		str: the type of this PDF field
		"""
		return self._type

	@property
	def value(self):
		"""
		any: the value stored in this PDF field
		"""
		return self._value


def get_pdf_field_list(pdf_reader):
	"""
	Makes representations of a PDF file's fields.

	Args:
		pdf_reader (PyPDF2.PdfFileReader): a reader that contains a PDF file's
			representation

	Returns:
		list: contains PdfField instances that represent the fields from the
			file read by pdf_reader
		None: if the file does not have fields
	"""
	pdf_fields = pdf_reader.getFields()
	if pdf_fields is None:
		return None

	field_list = list()
	for mapping_name, field in pdf_fields.items():
		field_list.append(PdfField(mapping_name, field.fieldType, field.value))

	return field_list


if __name__ == "__main__":
	try:
		input_path = Path(argv[1])
	except IndexError:
		input_path = None

	try:
		output_path = Path(argv[2])
	except IndexError:
		output_path = None

	output_path = check_io_path_pair(
		input_path, "Input file", ".pdf",
		output_path, "Output file", ".txt",
		"_field_values")

	reader = PdfFileReader(input_path.open(mode="rb"))
	field_list = get_pdf_field_list(reader)

	if field_list is None:
		print(str(input_path) + " does not contain fields.")
		exit()

	field_str = "\n".join(map(str, field_list))

	header = "Fields in file " + str(input_path) + "\n\n"
	output_path.write_text(header + field_str)