[Python-ideas] with statement vs. try...except...finally

[Gerald Britton]

I'm wondering if the "with" statement should have exception clauses
like the "try" statement, even though this seems to defeat part of the
reason for the "with" statement.

Currently I have a program segment that opens a file and reads a line,
something like this (distilled to its elements for illustration):

try:
    f = open('foo')
    line = f.readline()
    f.close()
except IOError:
    line = 'default'

So that I get a default value if anything goes awry whilst reading the file.

If I write it using a "with" statement, I might have:

line = 'default'
with open('foo') as f:
   line = f.readline()

Fine so far, but what if I want to be more granular?  e.g. with "try...except":

try:
    f = open('foo')
except IOError:
    line = "can't open"

try:
    line = f.readline()
except IOError:
    line = "can't read"

try:
    f.close()
except IOError:
    line = "can't close"

I can't see how to replace the above try-triplet with a "with"
encapsulation. Or, do I have to wrap the "with" statement in try like
this:

try:

  with open('foo') as f:
     line = f.readline()

except IOError:
  line = 'problem with read or close"


-- 
Gerald Britton