Python:以优雅的方式(代码保存)改进一个函数,以避免多个语句

时间:2012-10-25 17:12:39

标签: python performance optimization if-statement

我写了这个函数来读取Las文件并保存shapefile。该函数创建一个包含8个字段的shapefile。我希望在函数中插入解析元素,以便选择我希望保存LAS2SHP的字段(inFile,outFile = None,parse = None)。如果没有保存所有字段。如果解析是 parse =“irn”保存字段intensity,return_number和number_of_returns。跟随传奇

"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, 

我写了一个解决方案,如果.... ifelse ....其他真的代码消耗(而不是优雅)。感谢您提供有关保存代码的所有帮助和建议

提前谢谢 詹尼

这里是python中的原始函数

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)

1 个答案:

答案 0 :(得分:1)

也许尝试这样的事情:

    pdata = [p.z] + [getattr(p, pattr[key]) for key in parse]
    pdata = map(float, pdata)
    w.record(*pdata)
  • for key in parse循环遍历parse中的字母。例如, 如果parse = 'irn',则键循环显示值irn
  • pattr是一个词典。 pattr[key]是关联的名称 属性。例如,pattr['i']"intensity"
  • getattr(p, pattr[key])pattr[key]属性的值 在p。例如,getattr(p, "intensity")p.intensity。当您将属性的名称知道为字符串时,这是获取属性值的方法(例如pattr[key])。 *中的w.record(*pdata)在将参数发送到pdata之前解包w.record。例如,w.record(*[1,2,3])相当于w.record(1,2,3)。这是sends an arbitrary number of arguments to a function
  • 的方式

例如,

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)