#!/usr/bin/env python

##
# Create an SVG graph of BLS timeseries data using matplotlib and 
# BeautifulSoup.
#

import matplotlib.figure
import datetime
import bs4
import matplotlib.backends.backend_cairo
import string
import urllib2

def main():
	url = 'http://data.bls.gov/timeseries/%s?years_option=specific_years&include_graphs=true&to_year=2011&from_year=1948'
	total_series = 'LNS11300000'
	men_series = 'LNS11300001'
	women_series = 'LNS11300002'
	
	fig,ax = init_figure()
	add_plot(ax, scrape_bls(bs4.BeautifulSoup(urllib2.urlopen(url % total_series))), 'black')
	add_plot(ax, scrape_bls(bs4.BeautifulSoup(urllib2.urlopen(url % men_series))), 'lightblue')
	add_plot(ax, scrape_bls(bs4.BeautifulSoup(urllib2.urlopen(url % women_series))), 'pink')
	save_figure(fig, 'US Labor Participation Rate 1948-2011 by gender.svg')

##
# Scrape the BLS soup for the data.
#
def scrape_bls(soup):
	table = soup.find_all('table', attrs={'class': 'regular-data'})
	assert len(table) == 1
	table = table[0]
	data = []
	years_lc = [[t for t in r if type(t) is bs4.element.Tag] for r in table.contents[4] if type(r) is bs4.element.Tag]
	for row in years_lc:
		year = int(row[0].text)
		months = [float(t.text) for t in row[1:] if any(c in string.printable and c != ' ' for c in t.text)]
		data.append((year,months))
	return data

##
# Add plot to figure. Extra parameters are passed to 
# matplotlib.axes.Axes.plot().
#
def add_plot(axis, data, *args):
	x=[]
	y=[]
	for year,months in data:
		for month,n in enumerate(months):
			x.append(datetime.date(year, month+1, 1))
			y.append(n)
	axis.plot(x, y, *args)

##
# Initialize figure.
#
def init_figure():
	figure = matplotlib.figure.Figure()
	axis = figure.add_subplot(111)
	
	axis.xaxis.set_major_locator(matplotlib.dates.YearLocator(6))
	axis.xaxis.set_major_formatter(matplotlib.dates.DateFormatter('%Y'))
	
	axis.grid(True)
	
	return figure,axis

##
# Save figure
#
def save_figure(figure, filename):
	figure.canvas = matplotlib.backends.backend_cairo.FigureCanvasCairo(figure)
	figure.savefig(filename, transparent=True)

if __name__ == "__main__":
	main()