Peter J. Holzer wrote:
On 2019-11-04 18:18:39 -0300, Luciano Ramalho wrote:
In addition, as Rob said, it is usually a bad idea to wrap several
lines of code in a single try/except block
I disagree with this. While it is sometimes useful to wrap a single
line, in my experience it rarely is. The scope of the try ... except
should be a unit from a semantic point of view. For example, if you
open a file and write some data to it, you could write:
try:
f = open("a.file", "w")
except OSError as e:
... handle exception
try:
f.write("some")
except OSError as e:
... handle exception
try:
f.write("data")
except OSError as e:
... handle exception
try:
close(f)
except OSError as e:
... handle exception
But not only is this hard to read and ugly as heck, what would be the
point?
Much better to write:
try:
with open("a.file", "w") as f:
f.write("some")
f.write("data")
except OSError as e:
... handle exception
Or maybe don't catch it here at all but just let it bubble up until it
hits a level where dealing with it makes sense from the user's point of
view
Often it makes sense to do both -- catch the exception and
re-raise it with a more informative error message, e.g.
try:
with open(filename, "w") as f:
f.write("some")
f.write("data")
except OSError as e:
raise OSError("Couldn't write fibble data to %s: %s" % (filename, e))
That way you don't get frustrating Microsoft style error
messages which say "The system could not open the specified file"
while giving no clue about *which* file was specified... aarggh!
--
Greg
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