Read lighting data

Python ASCII file read functions could be used if the data can not be read by asciiread() and readtable() functions. Read data into several Python lists and create arrays from them for plotting.

fn = 'D:/Temp/ascii/lighting/2009_06_06.txt'
tf = open(fn)
lats = []
lons = []
vs = []
for aline in tf:
    datalist = aline.split()
    lat = float(datalist[3].split('=')[1])
    lon = float(datalist[4].split('=')[1])
    v = float(datalist[5].split('=')[1])
    lats.append(lat)
    lons.append(lon)
    vs.append(v)
lon = array(lons)
lat = array(lats)
v = array(vs)
axesm()
geoshow('cn_province')
ss = makesymbolspec('point', {'value':(-10000,0), 'color':'b', 'marker':'m', 'size':6, 'caption':'Negative'}, \
    {'value':(0,10000), 'color':'r', 'marker':'+', 'size':6, 'caption':'Positive'})
layer = scatter(lon, lat, v, symbolspec=ss)
legend(legend=layer.legend(), loc='lower left')
xlim(90, 130)
ylim(20, 50)
title('Lighting locations')