函数返回无-从列表

Question

我有以下功能：

def createListofParts(testbenchParts, testbench, ttype):
    partList = []
    for part in ttype:
        for root, subFolders, files in os.walk(os.path.join(testbenchParts, part)):
            for file in files:
                if file.endswith('.svn-base'):
                    pass
                elif file.endswith('all-wcprops'):
                    pass
                elif file.endswith('entries'):
                    pass
                else:
                    partList.append(os.path.join(root, file))
    createMatchTuples(partList, testbench)

def createMatchTuples(partList, testbench):
    XMLlist = glob.glob(os.path.join(testbench, 'Scripts', "*.xml"))
    matchList = []
    for part in partList:
        matches = 0
        for xmlFile in XMLlist:
            xml = open(xmlFile, 'r')
            t = re.findall('/' + os.path.split(part)[1], xml.read().replace('\\','/'))
            matches = matches + len(t)
            xml.close()
        matchList.append((os.path.split(part)[1], matches))
    print matchList
    print type(matchList)
    return matchList

这将打印一个元组列表，然后键入= List

这个功能叫做

matchList = functions.createListofParts(testbenchParts, testbench, ttype)
print matchList
print type(matchList)

但现在显示None，即matchList从第一个函数中的List转换为None！

我只是不明白这里发生了什么

任何帮助将不胜感激

Answer 1

createListofParts没有返回值，因此所有没有返回值的matchList = functions.createListofParts(testbenchParts, testbench, ttype)默认情况下返回None，所以matchList = functions.createListofParts(testbenchParts, testbench, ttype)将matchList设置为None ，您需要return createMatchTuples ：

def createListofParts(testbenchParts, testbench, ttype):
    partList = []
    for part in ttype:
        for root, subFolders, files in os.walk(os.path.join(testbenchParts, part)):
            for file in files:
                if file.endswith('.svn-base'):
                    pass
                elif file.endswith('all-wcprops'):
                    pass
                elif file.endswith('entries'):
                    pass
                else:
                    partList.append(os.path.join(root, file))
    return createMatchTuples(partList, testbench) # <- return

Answer 2

那是因为createListofParts没有return语句，并且在python中，默认情况下，如果没有return语句，则函数将返回None 。