Re: breaking from loop
Ritesh Raj Sarraf wrote: def copy_first_match(repository, filename, dest_dir): # aka walk_tree_copy() for path, file in files(repository): if file == filename: try: shutil.copy(os.path.join(path, file), dest_dir) sys.stdout.write(%s copied from local cache %s. % (file, repository)) except shutil.Error: sys.stdout.write(%s is available in %s. Skipping Copy! % (file, dest_dir)) return True return False All I've added is the exception check because in case file is available in dest_dir, I want to display a message. Since I'm still new and learning will be great if you let me know if this is the proper way or not. I prefer to let the exception propagate. As you wrote it, the code calling copy_first_match() has no way of knowing whether a file was copied or not. If you don't want to bother with exceptions in the calling code I'd slightly modify the try...except: try: # copy except (shutil.Error, OSError), e: # print failure message return False I. e. - catch OSError, too. I think shutil.copy() is more likely to raise an OSError than a shutil.Error. - return False if an exception occurs. That way you can test if something went wrong like so: if not copy_first_match(...): print file not found or unable to copy it Peter -- http://mail.python.org/mailman/listinfo/python-list
Re: breaking from loop
Ritesh Raj Sarraf enlightened us with: bFound = True break return bFound I see two weird things. First of all, the retun statement won't be reached due to the break before it. Let's assume the break isn't needed, and you want just the return. Why set the variable if you're going to return anyway? I'd change those three lines to return True. But since test directory is under temp, work_tree_copy makes two calls of the same function _but_ break only is able to get out from the inner call. Raise an exception and catch it at the outer level. Sybren -- The problem with the world is stupidity. Not saying there should be a capital punishment for stupidity, but why don't we just take the safety labels off of everything and let the problem solve itself? Frank Zappa -- http://mail.python.org/mailman/listinfo/python-list
Re: breaking from loop
Ritesh Raj Sarraf wrote:
Following is the code:
def walk_tree_copy(sRepository, sFile, sSourceDir, bFound = None):
try:
if sRepository is not None:
for name in os.listdir(sRepository):
path = os.path.join(sRepository, name)
if os.path.isdir(path):
walk_tree_copy(path, sFile, sSourceDir, bFound)
elif name.endswith('.foo') or name.endswith('.bar'):
if name == sFile:
Pick /one/ the conditions
- file name must be ...
- file must end with ... or ...
try:
shutil.copy(path, sSourceDir)
except IOError, (errno, errstring):
errfunc(errno, errstring)
except shutil.Error:
print name + is available in +
sSourceDir + Skipping Copy!
bFound = True
break
return bFound
except OSError, (errno, strerror):
print errno, strerror
This function allows me to walk into a directory based tree and search
for files ending with .foo and .bar. My requirement is to copy
.foo/.bar.
Say in directory temp=test=test.bar is found. So shutil.copy will
copy it. I want that once the copy is done, it should make bFound =
True and get out.
But since test directory is under temp, work_tree_copy makes two calls
of the same function _but_ break only is able to get out from the inner
call.
Where am I wrong in this code ? Is there a better way to implement it ?
An implementation on top of os.walk() can simplify things a bit:
import os
import shutil
def files(root):
for path, folders, files in os.walk(root):
for file in files:
yield path, file
def copy_first_match(repository, filename, dest_dir): # aka walk_tree_copy()
for path, file in files(repository):
if file == filename:
shutil.copy(os.path.join(path, file), dest_dir)
return True
return False
files() and os.walk() take care of the recursion, and you can just break or
return from the loop in copy_first_match().
Peter
--
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Re: breaking from loop
Ritesh Raj Sarraf wrote:
Hi,
Following is the code:
def walk_tree_copy(sRepository, sFile, sSourceDir, bFound = None):
try:
if sRepository is not None:
You're being overly defensive here. Passing None as first arg is clearly
a programming error, so the sooner you detect it the better. Hence, just
don't test, and let exceptions propagate.
for name in os.listdir(sRepository):
path = os.path.join(sRepository, name)
if os.path.isdir(path):
walk_tree_copy(path, sFile, sSourceDir, bFound)
elif name.endswith('.foo') or name.endswith('.bar'):
if name == sFile:
Why do you *first* test on the extension, and *then* on the whole name ?
The boolean expression:
(name.endswith('.foo') or name.endswith('.bar')) and name == sFile
logically implies that :
sFile.endswith('.foo') or sFile.endswith('.bar')
So the first test is pretty useless...
Also, why hardcode such tests ? Python makes it easy to write generic
(hence reusable) code.
try:
shutil.copy(path, sSourceDir)
except IOError, (errno, errstring):
errfunc(errno, errstring)
??? What is this function doing ?
except shutil.Error:
print name + is available in +
sSourceDir + Skipping Copy!
Don't assume the cause of the exception. FWIW, try the following snippet:
f = open('test.txt', 'w')
f.write('coucou')
f.close()
for i in range(10):
... shutil.copy('test.txt', 'testcopy.txt')
...
Also, stdout is meant to be used for normal program outputs. Other
messages should go to stderr.
bFound = True
break
return bFound
Err... this last statement won't be executed.
except OSError, (errno, strerror):
print errno, strerror
This function allows me to walk into a directory based tree and search
for files ending with .foo and .bar. My requirement is to copy
.foo/.bar.
Say in directory temp=test=test.bar is found. So shutil.copy will
copy it. I want that once the copy is done, it should make bFound =
True and get out.
What's the use of setting bFound to True ? If you want to get out
returning a value, just return that value :
# dummy exemple
def test(seq, target):
for item in seq:
if item == target:
return True
return False
But since test directory is under temp, work_tree_copy makes two calls
of the same function _but_ break only is able to get out from the inner
call.
You should first focus on making it work without worrying about error
handling. Ensure that all return path are covered (in your actual
implementation, your function always return None). Use a callback
function for testing if a file should be copied, so your code has a
chance of being reusable when specs evolve. And two hints:
* exceptions are not only for error handling, they are also useful to
control flow of execution...
* generators and iterators are great
AFAICT, what you're trying to do here is mainly to
1/ recursively search files matching a given condition in a directory tree
2/ do something with these files.
A solution could be to split your code accordingly:
def find_in_tree(tree_path, match):
join = os.path.join
isdir = os.path.isdir
isfile = os.path.isfile
for name in os.listdir(tree_path):
fpath = join(tree_path, name)
if isdir(fpath):
for foundpath in find_in_tree(fpath, match)
yield foundpath
elif isfile(fpath) and match(fpath):
yield fpath
raise StopIteration
def find_and_copy_to(tree_path,
dest_path, match,
stop_on_first_match=False):
done = []
for fpath in find_in_tree(tree_path, match):
if fpath not in done:
shutil.copy(fpath, dest_path)
done.append(fpath)
if stop_on_first_match:
break
return done
match_foo_bar = lambda fpath: \
fpath.endswith('.foo') or fpath.endswith('.bar')
done = find_and_copy_to(sRepository,
sSourceDir,
match_foo_bar,
stop_on_first_match=True)
NB1 : not tested
NB2: I'm not sure I clearly undestand your specs (you're mixing
functional specs and implementation details in your description of
you're trying to do), so this may not be exactly what you want...
Also some stylistic advices:
1/ hungarian notation is *evil* - and even worse in a dynamically typed
language. Better use explicit names. What's important is not the type of
a variable, but it's role.
2/ string formating is fine
print sys.stderr, \
%s is available in %s - skipping copy % (filename, source_dir)
Is there a better way to implement it ?
Probably. Anyway, the better implementation is usually no
implementation. What about:
find $Repository -name *.bar -exec cp {}
Re: breaking from loop
Thanks to everyone. It is really the best place and the best people to learn from. Here's what I followed from the discussion: def files(root): for path, folders, files in os.walk(root): for file in files: yield path, file def copy_first_match(repository, filename, dest_dir): # aka walk_tree_copy() for path, file in files(repository): if file == filename: try: shutil.copy(os.path.join(path, file), dest_dir) sys.stdout.write(%s copied from local cache %s. % (file, repository)) except shutil.Error: sys.stdout.write(%s is available in %s. Skipping Copy! % (file, dest_dir)) return True return False All I've added is the exception check because in case file is available in dest_dir, I want to display a message. Since I'm still new and learning will be great if you let me know if this is the proper way or not. Thanks to everyone once again. It's been a very good experience understanding everyone's comments. Regards, rrs -- http://mail.python.org/mailman/listinfo/python-list
Re: breaking from loop
Using the (non-standard yet) path module (http://www.jorendorff.com/articles/python/path/), your code can be simplified to: from path import path, copy def copy_first_match(repository, filename, dest_dir): try: first_match = path(repository).walkfiles(filename).next() except StopIteration: return False else: copy(first_match, dest_dir) return True I/O exceptions are left to propagate to the caller. George -- http://mail.python.org/mailman/listinfo/python-list
breaking from loop
Hi,
Following is the code:
def walk_tree_copy(sRepository, sFile, sSourceDir, bFound = None):
try:
if sRepository is not None:
for name in os.listdir(sRepository):
path = os.path.join(sRepository, name)
if os.path.isdir(path):
walk_tree_copy(path, sFile, sSourceDir, bFound)
elif name.endswith('.foo') or name.endswith('.bar'):
if name == sFile:
try:
shutil.copy(path, sSourceDir)
except IOError, (errno, errstring):
errfunc(errno, errstring)
except shutil.Error:
print name + is available in +
sSourceDir + Skipping Copy!
bFound = True
break
return bFound
except OSError, (errno, strerror):
print errno, strerror
This function allows me to walk into a directory based tree and search
for files ending with .foo and .bar. My requirement is to copy
.foo/.bar.
Say in directory temp=test=test.bar is found. So shutil.copy will
copy it. I want that once the copy is done, it should make bFound =
True and get out.
But since test directory is under temp, work_tree_copy makes two calls
of the same function _but_ break only is able to get out from the inner
call.
Where am I wrong in this code ? Is there a better way to implement it ?
Regards,
rrs
--
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