[Tutor] file exists question

[Wolfgang Maier]

On 09.03.2015 18:50, David Heiser wrote:
>
>
> On 3/9/2015 9:50 AM, Alan Gauld wrote:
>> Somebody posted a question asking how to fond out if a file
>> exists. The message was in the queue and I thought I'd approved
>> it but it hasn't shown up yet. Sorry to the OP if I've messed up.
>>
>> The answer is that you use the os.path.exists() function.
>> It takes a path as an argument which can be relative to
>> the cwd or absolute.
>>
>> HTH
>
> If you are testing for the existence of a file before opening it to read
> it, you can use exception testing instead.
>
>     try:
>          data = open(filename, 'r').read()
>     except NameError:
>          do something else
>

But why are you watching out for a NameError ?
FileNotFoundError would be appropriate in Python3.3 and later.
In earlier versions you could rewrite this as (I think):

try:
     data_in = open(filename, 'r')
except IOError:
     do somthing
data = data_in.read()

to make sure you are detecting a problem with opening the file 
independently of one reading from it.

Wolfgang