how do you know if open failed?

[SpreadTooThin]

f = open('myfile.bi n', 'rb')

How do I know if there was an error opening my file?

[tobiah]

Re: how do you know if open failed?

SpreadTooThin wrote:

f = open('myfile.bi n', 'rb')
>
How do I know if there was an error opening my file?
>

try:
open('noexist')
except:
print "Didn't open"

--
Posted via a free Usenet account from http://www.teranews.com

[Fredrik Lundh]

Re: how do you know if open failed?

SpreadTooThin wrote:

f = open('myfile.bi n', 'rb')
>
How do I know if there was an error opening my file?

you'll notice:

>>f = open("myfile.bi n", "rb")

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
IOError: [Errno 2] No such file or directory: 'myfile.bin'

>>>

</F>

[Neil Cerutti]

Re: how do you know if open failed?

On 2006-09-28, SpreadTooThin <bjobrien62@gma il.comwrote:

f = open('myfile.bi n', 'rb')
>
How do I know if there was an error opening my file?

Try it an see.

Seriously, it will raise an exception that you can catch.

try:
f = open('myfile.bi n', 'rb')
# Do stuff with f
except IOError, inst:
print 'Phooey.', inst.errno, inst.strerror

--
Neil Cerutti

[Erik Johnson]

Re: how do you know if open failed?


"tobiah" <toby@tobiah.or gwrote in message
news:451c0669$0 $19689$88260bb3 @free.teranews. com...

SpreadTooThin wrote:

f = open('myfile.bi n', 'rb')

How do I know if there was an error opening my file?

try:
open('noexist')
except:
print "Didn't open"

That's a way to trap any exception. I think a better answer to the
question is "You'll know if it didn't work because Python throws exceptions
when it runs into problems." You can catch exceptions and try to do
something about them if you want to. Uncaught exceptions cause the
interpreter to exit with a stack trace. Sometimes that's the most logical
thing to do.

>>fd = open('doesnt_ex ist', 'rb')

Traceback (most recent call last):
File "<stdin>", line 1, in ?
IOError: [Errno 2] No such file or directory: 'doesnt_exist'


It would throw a different exception if there were a permission problem, for
example.

-ej

[Bruno Desthuilliers]

Re: how do you know if open failed?

tobiah a écrit :

SpreadTooThin wrote:
>

>f = open('myfile.bi n', 'rb')
>>
>How do I know if there was an error opening my file?
>>

try:
open('noexist')
except:
print "Didn't open"
>

Should be:

try:
f = open('noexists' )
except IOError, e:
print >sys.stderr, "Failed to open 'noexists' : %s" % e