Tkinter 导致的无限循环问题

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华科云商小徐

发布于 2024-10-12 07:31:10

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代码可运行

文章被收录于专栏：小徐学爬虫小徐学爬虫

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代码可运行

在使用 Tkinter 时，出现无限循环问题通常与事件绑定、函数调用以及窗口更新循环的方式有关。Tkinter 是一个事件驱动的 GUI 库，它依赖主循环 (mainloop()) 来处理用户交互和事件。如果代码的某一部分引发了循环或递归调用，可能会导致无限循环或应用程序无响应。

1、问题背景

我有一个脚本，在添加了用于用户交互的文件查询框之前一直运行良好。现在，它会不断重复询问问题，只有当强制使以下命令 (shutil.copy2) 崩溃（通过使输入/输出文件相同）时才退出。为什么会这样？

import os, xml, arcpy, shutil, datetime, Tkinter,tkFileDialog
from xml.etree import ElementTree as et

path=os.getcwd()
RootDirectory=path
arcpy.env.workspace = path
Count=0

Generated_XMLs=RootDirectory+'\GeneratedXML_LOG.txt'
f = open(Generated_XMLs, 'a')
f.write("Log of Metadata Creation Process - Update: "+str(datetime.datetime.now())+"\n")
f.close()

for root, dirs, files in os.walk(RootDirectory, topdown=False):
    #print root, dirs
    for directory in dirs:
        currentPath=os.path.join(root,directory)
        os.chdir(currentPath)
        arcpy.env.workspace = currentPath
        print currentPath
#def Create_xml(currentPath):

        FileList = arcpy.ListFeatureClasses()
        zone="_Zone"

        for File in FileList:
            Count+=1
            FileDesc_obj = arcpy.Describe(File)
            FileNm=FileDesc_obj.file
            print FileNm

            check_meta=os.listdir(currentPath)
            existingXML=FileNm[:FileNm.find('.')]
            existingExtension=FileNm[FileNm.find('.'):]
            print "XML: "+existingXML
            print check_meta
            #if  existingXML+'.xml' in check_meta:
            for f in check_meta:
             if f.startswith(existingXML) and f.endswith('.xml'):
                print "exists, file name:", f
                newMetaFile=FileNm+"_2012Metadata.xml"
                shutil.copy2(f, newMetaFile)

代码导致循环
     else:
        #print "Does not exist"
        newMetaFile=FileNm+"_BaseMetadata.xml"
        root = Tkinter.Tk()
        file = tkFileDialog.askopenfile(parent=root,mode='rb',title='Choose a xml base file to match with: '+File)
        if file != None:
             metafile=os.path.abspath(file.name)
             file.close()
             print metafile
             shutil.copy2(metafile,newMetaFile)
             print "copied"
        else:
        shutil.copy2('L:\Data_Admin\QA\Metadata_python_toolset\Master_Metadata.xml', newMetaFile)

    tree=et.parse(newMetaFile)        
    print "Processing: "+str(File)  

剩下的工作代码
            for node in tree.findall('.//title'):
                node.text = str(FileNm)
            for node in tree.findall('.//northbc'):
                node.text = str(FileDesc_obj.extent.YMax)
            for node in tree.findall('.//southbc'):
                node.text = str(FileDesc_obj.extent.YMin)
            for node in tree.findall('.//westbc'):
                node.text = str(FileDesc_obj.extent.XMin)
            for node in tree.findall('.//eastbc'):
                node.text = str(FileDesc_obj.extent.XMax)        
            for node in tree.findall('.//native/nondig/formname'):
                node.text = str(os.getcwd()+"\\"+File)
            for node in tree.findall('.//native/digform/formname'):
                node.text = str(FileDesc_obj.featureType)
            for node in tree.findall('.//avlform/nondig/formname'):
                node.text = str(FileDesc_obj.extension)
            for node in tree.findall('.//avlform/digform/formname'):
                node.text = str(float(os.path.getsize(File))/int(1024))+" KB"
            for node in tree.findall('.//theme'):
                node.text = str(FileDesc_obj.spatialReference.name +" ; EPSG: "+str(FileDesc_obj.spatialReference.factoryCode))
            print node.text
            projection_info=[]
            Zone=FileDesc_obj.spatialReference.name

            if "GCS" in str(FileDesc_obj.spatialReference.name):
                projection_info=[FileDesc_obj.spatialReference.GCSName, FileDesc_obj.spatialReference.angularUnitName, FileDesc_obj.spatialReference.datumName, FileDesc_obj.spatialReference.spheroidName]
                print "Geographic Coordinate system"
            else:
                projection_info=[FileDesc_obj.spatialReference.datumName, FileDesc_obj.spatialReference.spheroidName, FileDesc_obj.spatialReference.angularUnitName, Zone[Zone.rfind(zone)-3:]]
                print "Projected Coordinate system"
            x=0
            for node in tree.findall('.//spdom'):
                for node2 in node.findall('.//keyword'):
                    print node2.text
                    node2.text = str(projection_info[x])
                    print node2.text
                    x=x+1


            tree.write(newMetaFile)

            f = open(Generated_XMLs, 'a')
            f.write(str(Count)+": "+File+"; "+newMetaFile+"; "+currentPath+"\n")
            f.close()



    #        Create_xml(currentPath)

2、解决方案

这个问题是由使用 tkFileDialog.askopenfile() 函数引起的，它会打开一个文件选择对话框，允许用户选择一个文件。但是，如果没有选择文件，file 变量将为 None，并且 shutil.copy2() 函数将在没有源文件的情况下尝试复制文件，这会导致无限循环。

为了解决这个问题，需要在使用 shutil.copy2() 函数之前检查 file 变量是否为 None。如果为 None，则需要执行其他操作，例如显示错误消息或退出脚本。

以下是我修改后的代码示例：

import os, xml, arcpy, shutil, datetime, Tkinter,tkFileDialog
from xml.etree import ElementTree as et

path=os.getcwd()
RootDirectory=path
arcpy.env.workspace = path
Count=0

Generated_XMLs=RootDirectory+'\GeneratedXML_LOG.txt'
f = open(Generated_XMLs, 'a')
f.write("Log of Metadata Creation Process - Update: "+str(datetime.datetime.now())+"\n")
f.close()

for root, dirs, files in os.walk(RootDirectory, topdown=False):
    #print root, dirs
    for directory in dirs:
        currentPath=os.path.join(root,directory)
        os.chdir(currentPath)
        arcpy.env.workspace = currentPath
        print currentPath
#def Create_xml(currentPath):

        FileList = arcpy.ListFeatureClasses()
        zone="_Zone"

        for File in FileList:
            Count+=1
            FileDesc_obj = arcpy.Describe(File)
            FileNm=FileDesc_obj.file
            print FileNm

            check_meta=os.listdir(currentPath)
            existingXML=FileNm[:FileNm.find('.')]
            existingExtension=FileNm[FileNm.find('.'):]
            print "XML: "+existingXML
            print check_meta
            #if  existingXML+'.xml' in check_meta:
            for f in check_meta:
             if f.startswith(existingXML) and f.endswith('.xml'):
                print "exists, file name:", f
                newMetaFile=FileNm+"_2012Metadata.xml"
                shutil.copy2(f, newMetaFile)

代码导致循环
     else:
        #print "Does not exist"
        newMetaFile=FileNm+"_BaseMetadata.xml"
        root = Tkinter.Tk()
        file = tkFileDialog.askopenfile(parent=root,mode='rb',title='Choose a xml base file to match with: '+File)
        if file != None:
             metafile=os.path.abspath(file.name)
             file.close()
             print metafile
             shutil.copy2(metafile,newMetaFile)
             print "copied"
        else:
             print "No file selected. Exiting..."
             sys.exit(0)

    tree=et.parse(newMetaFile)        
    print "Processing: "+str(File)  

剩下的工作代码
            for node in tree.findall('.//title'):
                node.text = str(FileNm