Python will not print even test strings after calling a join. Executes with code 0 though

Question

I am writing some Python code to rename some files. In doing so, I have ran across a peculiar error. When I try to print anything after my join, nothing will print. Not even print 'test' .

What could be causing this? Here is the code :

       ... #finding all images in a .html
       for t in soup.find_all('img'):                    # Note: soup exists outside of with
            try:
                old_src = t['src']                        # Access src attribute
                image = os.path.split(old_src)[1]         # Get file name
                #print 'image => ' + image

                relpath = os.path.relpath(root, do)       # Get relative path from do to root
                folders = relpath.strip('\\').split('\\') # Remove outer slashes, split on folder separator
                #BELOW LINE CAUSES PROBLEM
                new_src = '_'.join(folders.append(str(image))) # Join folders and image by underscore
                print t['src'] #prints nothing
                print 'test' #prints nothing
                t['src'] = new_src                        # Modify src attribute
            except:                                       # Do nothing if tag does not have src attribute
                pass

It confuses me that nothing prints below this line, as it clearly reaches the end of execution...it will not do anything after this line though as far as I can see. Execution stops completely.

Can anyone see any issue here?

Thanks.

Answer 1

folders.append(str(image)) returns nothing ( None ), so the program would raise an exception and skip your print statements.

You can solve it simply by replacing your new_src = '_'.join(folders.append(str(image))) with two following lines:

folders.append(str(image))
new_src = '_'.join(folders) 

If you catch exception by except Exception as e: and print e , you will see the TypeError error message, because it's same as doing '_'.join(None) by executing '_'.join(folders.append(str(image)))

Answer 2

假设folders是一个正常的list ， folders.append返回None ，但str.join预计可迭代作为它的参数，所以它提出了一个TypeError ......然后将其捕获并通过您的忽视except: pass ，之后继续执行下下一个t in soup.find_all('img') ，因此永远不会到达print位置。