[IceNine]

I'm new to Python, well versed in PHP and a bit of Perl.

I've written a simple backup utility that FTPs from one server to another. I'd like to implement exception handling on the FTP should someting go wrong.

This is basically what I have so far:

try:
  	ftp = FTP(ftp_host, ftp_user, ftp_pass)
  	ftp.storbinary('STOR ' + filename, pointer)
  	ftp.close()
  except:

I'd like to use 'all_errors' documented here.html but I don't know how! Will I have to create a handler for each other exception?

[jacktasia]

import ftplib
try:
	ftp = ftplib.FTP('ftp.cwi.nl')   # change to invalid address to test
        # user anonymous, passwd anonymous@
	ftp.login()               
	ftp.retrlines('LIST')     # change from LIST to invalid command to test
except ftplib.all_errors:
	print "an error occured" #error message for any error.

here you go. make the changes to the right to test it out

[Yegg`]

Why use except ftplib.all_errors: when just plain old except is doing the same thing? Or can except ftplib.all_errors print out specific errors?

[hydroxide]

Originally Posted by †Yegg†

Why use except ftplib.all_errors: when just plain old except is doing the same thing? Or can except ftplib.all_errors print out specific errors?

A bare except does NOT do the same thing, as it will catch errors which it shouldn't (which is why, except in rare cases such top-level error handling/logging, you should not use them). For instance:

try:
    abc = 1
    abc = do_something_with(acb)
except:
    abc = 4

will always make abc 4. it would be much better if NameError were raised at this point. Bare excepts lead to subtle hard to track errors.

--OH.

[IceNine]

I wanted to email myself the error when/if it happened, so this is what I ended up with:

try:
   	ftp.connect(ftp_host)
   	ftp.login(ftp_user, ftp_pass)
   	ftp.storbinary("STOR " + filename, pointer)
   	ftp.close()
   except Exception, e:
   	err_msg = "Headers and stuff here"
   	for arg in e.args:
   		err_msg = err_msg + str(arg) + "\n"
   
   	from smtplib import SMTP
   	mFrom = 'alert@*.com'
   	mTo   = myemail@***.com
   
   	mailer = SMTP('mail.***.com')
   	mailer.sendmail(mFrom, mTo, err_msg)

[hydroxide]

Originally Posted by IceNine

I wanted to email myself the error when/if it happened, so this is what I ended up with:

    err_msg = "Headers and stuff here"
    for arg in e.args:
        err_msg = err_msg + str(arg) + "\n"

That code won't work properly unless there's only one arg in e.args. If there's only one, use string formats:

    err_header = "Header text\n"
    err_body = "body intro: %s\n"%(e.args[0])
    err_msg = err_header + err_body

If there's more than one, use a list comp and string formats:

    err_header = "Header text"
    err_body = ["body intro: %s"%(arg)
                for arg in e.args]       
    err_msg = err_header + "".join(err_body)

--OH.