[Tutor] I need to ignore an error let the script continue to run

[Jim]

On 5/5/20 3:01 AM, Alan Gauld via Tutor wrote:
> On 05/05/2020 03:41, Jim wrote:
> 
>> It seems try/except will not process the keys after the missing one.
> 
> You need to wrap each bit that needs to continue in try/except.
> Clunky I agree.
> 
>> 'Recepient username: ' + header['to'].addresses[0].username+'\n',
>> 'Sender name: ' + header['from'].addresses[0].display_name
>>
>> They don't look like keys, but they do resolve to the info I want if it
>> is in the header.
> 
> They aren't keys they are accessing attributes of some class that is
> returned. You could check the return value from header first using an if
> test. Or you could just wrap those two calls in their own try/except.
> 
> Or you could use get() and return a dummy instance of whatever class it
> is with whatever default values you need.
> 
> So several solutions only you can decide which suits you best.

OK, thanks, I'll give them a try and see which on works best.

>> def parse_header(msg):
>>       with open('/home/jfb/' + email_msg, 'rb') as fp:
>>           header = BytesParser(policy=default).parse(fp)
>>           #  Now the header items can be accessed as a dictionary:
>>       try:
>>           headers = [>          'To: ' + header['to']+'\n' ,
> 
> Notice you access header['to'] here and print it directly.
> 
>>           'Recepient username: ' +
>> header['to'].addresses[0].username+'\n',
> 
> But here you try to access attributes.
> You can't have it both ways. Either its a printable string
> or its an object with an addresses list...
> If you do get a header with an object the first use is likely to break..

When I started looking in to doing this I googled and one of the first 
hits was the Python docs. This function was based on of the examples. It 
did about 95% of what I wanted to do with out modification.

It looks that way but they actually return slightly different 
information. I just ran it against a message with all the elements in 
the header to verify it.

> 
>>           msg_header = []
>>
>>           for item in headers:
>>               msg_header.append(item)
> 
> This would be easier as a list comprehension:
> 
> msg_header = [item for item in headers]
> 
> But given its just a direct copy it would be easier still with
> 
> msg_header = headers[:]
> 

Thanks, I always have trouble understanding some of the more complex 
list comprehension so I guess I don't even think about the simpler one 
like this one. I completely forgot about [:].

Thanks,  Jim