On Monday 28 November 2016 17:09, Ganesh Pal wrote:
> Dear Python friends,
>
> Any suggestion on how to add exception and make the below program look
> better , I am using Python 2.7 and Linux
>
> ------------------------------------------------------------
> --------------------------------
>
> def create_files_append():
> """ """
> try:
> os.makedirs(QA_TEST_DIR)
> except:
> raise OSError("Can't create directory (%s)!" % (QA_TEST_DIR))
>
> # Create few files and write something
> for i in range(1000):
> with open(os.path.join(QA_TEST_DIR,"filename%d" %i),'w') as f:
> f.write("hello")
>
> # Append the files
> for i in range(1000):
> with open(os.path.join(QA_TEST_DIR,"filename%d" %i),'w') as f:
> f.write("hello")
>
> return True
There is no need to return True. The function either succeeds, or it raises an
exception, so there is no need to return any value at all.
There is no need to catch the exception if you're not going to do anything with
it. os.makedirs already raises OSError if there is a problem creating the
directories, so all you are doing is catching a sensible, useful error message
that tells you WHY it failed with a useless, generic error message that tells
you nothing.
py> os.makedirs('/root/xyz')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/local/lib/python2.7/os.py", line 157, in makedirs
mkdir(name, mode)
OSError: [Errno 13] Permission denied: '/root/xyz'
Permission denied is *much* more useful than "cannot create directory".
Your comment says "append the files", but you're not appending to the files,
you are overwriting them. So your code is better written like this:
def create_files_append():
"""Docstring"""
os.makedirs(QA_TEST_DIR)
# Create few files and write something
for i in range(1000):
with open(os.path.join(QA_TEST_DIR,"filename%d" %i),'w') as f:
f.write("hello")
If you really want to create the file, close the file, then append to it, you
can do this:
def create_files_append():
"""Docstring"""
os.makedirs(QA_TEST_DIR)
# Create few files and write something
for i in range(1000):
with open(os.path.join(QA_TEST_DIR,"filename%d" %i),'w') as f:
f.write("hello")
# Append to the files
for i in range(1000):
with open(os.path.join(QA_TEST_DIR,"filename%d" %i),'a') as f:
f.write("hello")
but that's a waste of time, this is better:
def create_files_append():
"""Docstring"""
os.makedirs(QA_TEST_DIR)
# Create few files and write something
for i in range(1000):
with open(os.path.join(QA_TEST_DIR,"filename%d" %i),'w') as f:
f.write("hellohello")
If you want to skip any files that can't be opened:
def create_files_append():
"""Docstring"""
os.makedirs(QA_TEST_DIR)
# Create few files and write something
for i in range(1000):
try:
with open(os.path.join(QA_TEST_DIR,"filename%d" %i),'w') as f:
f.write("hellohello")
except (OSError, IOError):
pass
> What will be the best way to catch the exception in the above program ?
Not catching it at all.
> Can we replace both the with statement in the above program with something
> like below
>
> try:
> for i in range(1000):
> with open(os.path.join(QA_TEST_DIR,"filename%d" %i),'w') as f:
> f.write("hello")
> except IOError as e:
> raise
What's the point of that? All you are doing is catching the exception and then
immediately raising it again. That's the same as not catching it.
--
Steven
"Ever since I learned about confirmation bias, I've been seeing
it everywhere." - Jon Ronson
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