Question

I wrote this function to read Las file and save a shapefile. The function creates a shapefile with 8 fields. What i wish insert a parse element in the function in order to select the fields i wish to save LAS2SHP(inFile,outFile=None,parse=None). if None all fields are saved. if parse is
parse=”irn” the fields intensity, return_number, and number_of_returns are saved. following the legend

"i": p.intensity,
"r": p.return_number,
"n": p.number_of_returns,
"s": p.scan_direction,
"e": p.flightline_edge,
"c": p.classification,
"a": p.scan_angle, 

I wrote a solution if….ifelse….else really code consuming (and not elegant). Thanks for all helps and suggestions for saving code

thanks in advance
Gianni

here the original function in python

import shapefile
from liblas import file as lasfile

def LAS2SHP(inFile,outFile=None):
    w = shapefile.Writer(shapefile.POINT)
    w.field('Z','C','10')
    w.field('Intensity','C','10')
    w.field('Return','C','10')
    w.field('NumberRet','C','10')
    w.field('ScanDir','C','10')
    w.field('FlightEdge','C','10')
    w.field('Class','C','10')
    w.field('ScanAngle','C','10')
    for p in lasfile.File(inFile,None,'r'):
        w.point(p.x,p.y)
        w.record(float(p.z),float(p.intensity),float(p.return_number),float(p.number_of_returns),float(p.scan_direction),float(p.flightline_edge),float(p.classification),float(p.scan_angle))
    if outFile == None:
        inFile_path, inFile_name_ext = os.path.split(os.path.abspath(inFile))
        inFile_name = os.path.splitext(inFile_name_ext)[0]
        w.save("{0}\\{1}.shp".format(inFile_path,inFile_name))
    else:
        w.save(outFile)

Answer 1

Perhaps try something like this:

    pdata = [p.z] + [getattr(p, pattr[key]) for key in parse]
    pdata = map(float, pdata)
    w.record(*pdata)

• for key in parse loops through the letters in parse. For example,
  if parse = 'irn' then key loops through the values i, r, n.
• pattr is a dict. pattr[key] is the name of the associated
  attribute. For example, pattr['i'] is "intensity".
• getattr(p, pattr[key]) is the value of the pattr[key] attribute
  in p. For example, getattr(p, "intensity") is p.intensity. It is the way to get attribute values when you know the name of the attribute as a string, (e.g. pattr[key]).
  The * in w.record(*pdata) unpacks pdata before sending the arguments on to w.record. For example, w.record(*[1,2,3]) is equivalent to w.record(1,2,3). It is the way one sends an arbitrary number of arguments to a function.

---

For example,

import shapefile
from liblas import file as lasfile

pattr = {
    "i": 'intensity',
    "r": 'return_number',
    "n": 'number_of_returns',
    "s": 'scan_direction',
    "e": 'flightline_edge',
    "c": 'classification',
    "a": 'scan_angle',
    }

wattr = {
    "i": 'Intensity',
    "r": 'Return',
    "n": 'NumberRet',
    "s": 'ScanDir',
    "e": 'FlightEdge',
    "c": 'Class',
    "a": 'ScanAngle',
    }

def LAS2SHP(inFile, outFile=None, parse = 'irnseca'):
    w = shapefile.Writer(shapefile.POINT)
    w.field('Z','C','10')
    for key in parse:
        w.field(wattr[key],'C','10')
    for p in lasfile.File(inFile,None,'r'):
        w.point(p.x,p.y)
        pdata = [p.z] + [getattr(p, pattr[key]) for key in parse]
        pdata = map(float, pdata)
        w.record(*pdata)       
    if outFile == None:
        inFile_path, inFile_name_ext = os.path.split(os.path.abspath(inFile))
        inFile_name = os.path.splitext(inFile_name_ext)[0]
        w.save("{0}\\{1}.shp".format(inFile_path,inFile_name))
    else:
        w.save(outFile)