函数返回无

Question

我有以下脚本：

def collectUserPrompt():  

    xml_file = raw_input('Enter the full file path (ex: C:\Users\Stan\Documents\myxml.xml):') 

    try: 
     os.path.isfile(xml_file) 
     print 'good path' 
    except: 
     print "Please enter a valid xml file path!" 
     collectUserPrompt() 

    multiplier_input = raw_input('Enter XML multiplier (numbers only):') 
    try: 
     multiplier = int(multiplier_input) 
     print 'good multiplier' 
    except : 
     print "Please enter a valid integer!" 
     collectUserPrompt() 

     return xml_file, multiplier 

user_input = collectUserPrompt() 
print user_input 

当我跑，我得到：

Enter the full file path (ex: C:\Users\LIDMZ3W\Documents\myxml.xml):C:\Users\Stan\Documents\Aptana Studio 3 Workspace\ADFTest\src\Training\nascoUMBY.xml 
good path 
Enter XML multiplier (numbers only):3 
good multiplier 
None 

它看起来像我每次回国None，当我试图从raw_input函数返回验证的用户输入。

Answer 1

您的return声明位于except区块中。看起来好像你打算直接在函数的块中。也就是说，你需要在缩进时将它取回一级：

def collectUserPrompt():  

    xml_file = raw_input('Enter the full file path (ex: C:\Users\Stan\Documents\myxml.xml):') 

    try: 
     os.path.isfile(xml_file) 
     print 'good path' 
    except: 
     print "Please enter a valid xml file path!" 
     collectUserPrompt() 

    multiplier_input = raw_input('Enter XML multiplier (numbers only):') 
    try: 
     multiplier = int(multiplier_input) 
     print 'good multiplier' 
    except : 
     print "Please enter a valid integer!" 
     collectUserPrompt() 

    return xml_file, multiplier # here!