dougal-software/bin/legacy_fwr.py

#!/usr/bin/python3

"""
Legacy fixed width record importing functions.
"""

import builtins

def parse_fwr (string, widths, start=0):
	"""Parse a fixed-width record.

	string: the string to parse.
	widths: a list of record widths. A negative width denotes a field to be skipped.
	start: optional start index.

	Returns a list of strings.
	"""
	results = []
	current_index = start
	for width in widths:
		if width > 0:
			results.append(string[current_index : current_index + width])
			current_index += width
		else:
			current_index -= width

	return results

def int (v):
	return builtins.int(float(v))

def parse_line (string, spec):
	"""Parse a line from an SPS file."""
	names = spec["names"]
	widths = spec["widths"]
	normalisers = spec["normalisers"]
	record = [ t[0](t[1]) for t in zip(normalisers, parse_fwr(string, widths)) ]
	return dict(zip(names, record))

def from_file(path, spec = None):
	if spec is None:
		spec = {
			"names": [ "line_name", "point_number", "easting", "northing" ],
			"widths": [ -1, 10, 10, -25, 10, 10 ],
			"normalisers": [ int, int, float, float ]
		}
	else:
		normaliser_tokens = [ "int", "float", "str", "bool" ]
		spec["normalisers"] = [ eval(t) for t in spec["types"] if t in normaliser_tokens ]

	records = []
	with open(path) as fd:
		cnt = 0
		line = fd.readline()
		while line:
			cnt = cnt+1

			if line == "EOF":
				break

			record = parse_line(line, spec)
			if record is not None:
				records.append(record)

			line = fd.readline()

	del spec["normalisers"]
	return records