尝试，但两者都被另一个函数调用时执行

Question

There's something weird happening with my code, I have a first function that goes like this :

def function1():
    try : #1
        #try to open a file
        #read file
        #return info variable from the file
    except : #1
        try : #2
            #try to open a web page
            #read web page
            if directory1 not in directorylist :
                #create directory1
                #change working directory to directory1
            else :
                #change working directory to directory1
            #write web page content in a file
            #return info variable from the file
        except : #2
            try : #3
                #try to open a second web page
                #print error message 1
            except : #3
                #print error message 2
        #set info variable to None
        #return info variable

So this function works perfectly when called in the main program, but when I try to call function1 in another function2, both try#2 and except#2 are executed ! Cause directory1 is created and error message 1 is printed, also my info variable equals None.

How can calling function1 in a second function mess try and except clauses ?

Thank you !

Answer 1

Why is it surprising? try block is supposed to execute till some exception is raised and after that except block will execute. So why does it look like both blocks got executed in spite of an exception ?

One of the most likely reasons is there are stuff in try block that has nothing to do with the exception being raised. That's the primary reason for the else block. Refactoring your code as follows might help

try:
    # only statements that might raise exception
except SomeException:
    # except block
else:
    # everything you wanted do if no exception was raised

If it's a big chunk of code, fatter the else block, things are likely to go smoothly.

Answer 2

If an exception is raised while executing body of try #2 , obviously except #2 will be executed. You probably should check what kind of exception is raised and at which line.