RE: making a valid file name...
Hi I'm writing a python script that creates directories from user
input.
Sometimes the user inputs characters that aren't valid
characters for a
file or directory name.
Here are the characters that I consider to be valid characters...
valid =
':./,^0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ '
if I have a string called fname I want to go through each character in
the filename and if it is not a valid character, then I want
to replace
it with a space.
This is what I have:
def fixfilename(fname):
valid =
':.\,^0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ '
for i in range(len(fname)):
if valid.find(fname[i]) 0:
fname[i] = ' '
return fname
Anyone think of a simpler solution?
I got;
import re
badfilename='£%^£^£$^ihgeroighroeig3645^£$^knovin98u4#346#1461461'
valid=':./,^0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ '
goodfilename=re.sub('[^'+valid+']',' ',badfilename)
goodfilename
' ^ ^ ^ihgeroighroeig3645^ ^ knovin98u4 346 1461461'
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Re: making a valid file name...
Matthew Warren wrote:
import re
badfilename='£%^£^£$^ihgeroighroeig3645^£$^knovin98u4#346#1461461'
valid=':./,^0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ '
goodfilename=re.sub('[^'+valid+']',' ',badfilename)
to create arbitrary character sets, it's usually best to run the character
string through
re.escape() before passing it to the RE engine.
/F
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Re: making a valid file name...
You should use the s.translate() It's 100x faster: #Creates the translation table ValidChars = :./,^0123456789abcdefghijklmnopqrstuvwxyz InvalidChars = .join([chr(i) for i in range(256) if not chr(i).lower() in ValidChars]) TranslationTable = .join([chr(i) for i in range(256)]) def valid_filename(fname): return fname.translate(TranslationTable, InvalidChars) valid = ':./,^0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ ' if I have a string called fname I want to go through each character in the filename and if it is not a valid character, then I want to replace it with a space. -- Ceci est une signature automatique de MesNews. Site : http://www.mesnews.net -- http://mail.python.org/mailman/listinfo/python-list
Re: making a valid file name...
Tim Chase: In practice, however, for such small strings as the given whitelist, the underlying find() operation likely doesn't put a blip on the radar. If your whitelist were some huge document that you were searching repeatedly, it could have worse performance. Additionally, the find() in the underlying C code is likely about as bare-metal as it gets, whereas the set membership aspect of things may go through some more convoluted setup/teardown/hashing and spend a lot more time further from the processor's op-codes. With this specific test (half good half bad), on Py2.5, on my PC, sets start to be faster than the string search when the string good is about 5-6 chars long (this means set are quite fast, I presume). from random import choice, seed from time import clock def main(choice=choice): seed(1) n = 10 for good in (ab, abc, abcdef, abcdefgh, abcdefghijklmnopqrstuvwxyz): poss = good + good.upper() data = [choice(poss) for _ in xrange(n)] * 10 print len(good) = , len(good) t = clock() for c in data: c in good print round(clock()-t, 2) t = clock() sgood = set(good) for c in data: c in sgood print round(clock()-t, 2), \n main() Bye, bearophile -- http://mail.python.org/mailman/listinfo/python-list
Re: making a valid file name...
On 2006-10-18, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: Tim Chase: In practice, however, for such small strings as the given whitelist, the underlying find() operation likely doesn't put a blip on the radar. If your whitelist were some huge document that you were searching repeatedly, it could have worse performance. Additionally, the find() in the underlying C code is likely about as bare-metal as it gets, whereas the set membership aspect of things may go through some more convoluted setup/teardown/hashing and spend a lot more time further from the processor's op-codes. With this specific test (half good half bad), on Py2.5, on my PC, sets start to be faster than the string search when the string good is about 5-6 chars long (this means set are quite fast, I presume). from random import choice, seed from time import clock def main(choice=choice): seed(1) n = 10 for good in (ab, abc, abcdef, abcdefgh, abcdefghijklmnopqrstuvwxyz): poss = good + good.upper() data = [choice(poss) for _ in xrange(n)] * 10 print len(good) = , len(good) t = clock() for c in data: c in good print round(clock()-t, 2) t = clock() sgood = set(good) for c in data: c in sgood print round(clock()-t, 2), \n main() On my Python2.4 for Windows, they are often still neck-and-neck for len(good) = 26. set's disadvantage of having to be constructed is heavily amortized over 100,000 membership tests. Without knowing the usage pattern, it'd be hard to choose between them. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: making a valid file name...
I would suggest something like string.maketrans http://docs.python.org/lib/node41.html. I don't remember exactly how it works, but I think it's something like invalid_chars = abc replace_chars = 123 char_map = string.maketrans(invalid_chars, replace_chars) filename = abc123.txt filename.translate(charmap) '123123.txt' -- Jerry -- http://mail.python.org/mailman/listinfo/python-list
Re: making a valid file name...
SpreadTooThin wrote: Hi I'm writing a python script that creates directories from user input. Sometimes the user inputs characters that aren't valid characters for a file or directory name. Here are the characters that I consider to be valid characters... valid = ':./,^0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ ' if I have a string called fname I want to go through each character in the filename and if it is not a valid character, then I want to replace it with a space. This is what I have: def fixfilename(fname): valid = ':.\,^0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ ' for i in range(len(fname)): if valid.find(fname[i]) 0: fname[i] = ' ' return fname Anyone think of a simpler solution? If you want to strip 'em: valid=':./,^0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ ' filename = '!£!£$$££$%$£%$£lasfjalsfjdlasfjasfd()()()somethingelse.dat' stripped = ''.join(c for c in filename if c in valid) stripped 'lasfjalsfjdlasfjasfdsomethingelse.dat' If you want to replace them with something, be careful of the regex string being built (ie a space character). import re re.sub(r'[^%s]' % valid,' ',filename) ' lasfjalsfjdlasfjasfd somethingelse.dat' Jon. -- http://mail.python.org/mailman/listinfo/python-list
Re: making a valid file name...
Sometimes the user inputs characters that aren't valid characters for a file or directory name. Here are the characters that I consider to be valid characters... valid = ':./,^0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ ' Just a caveat, as colons and slashes can give grief on various operating systems...combined with periods, it may be possible to cause trouble too... This is what I have: def fixfilename(fname): valid = ':.\,^0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ ' for i in range(len(fname)): if valid.find(fname[i]) 0: fname[i] = ' ' return fname Anyone think of a simpler solution? I don't know if it's simpler, but you can use fname = this is a test it ain't expen$ive.py ''.join(c in valid and c or ' ' for c in fname) 'this is a test it ain t expen ive.py' It does use the it's almost a ternary operator, but not quite method concurrently being discussed/lambasted in another thread. Treat accordingly, with all that may entail. Should be good in this case though. If you're doing it on a time-critical basis, it might help to make valid a set, which should have O(1) membership testing, rather than using the in test with a string. I don't know how well the find() method of a string performs in relationship to in testing of a set. Test and see, if it's important. -tkc -- http://mail.python.org/mailman/listinfo/python-list
Re: making a valid file name...
Hi,
On 10/17/2006 06:22:45 PM, SpreadTooThin wrote:
valid =
':./,^0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ '
not specifying the OS platform, these are not all the characters
that may occur in a filename: '[]{}-=, etc. And '/' is NOT valid.
On a unix platform. And it should be easy to scan the filename and
check every character against the 'valid-string'.
HTH, cu l8r, Edgar.
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Re: making a valid file name...
On 2006-10-17, Tim Chase [EMAIL PROTECTED] wrote: If you're doing it on a time-critical basis, it might help to make valid a set, which should have O(1) membership testing, rather than using the in test with a string. I don't know how well the find() method of a string performs in relationship to in testing of a set. Test and see, if it's important. The find method of (8-bit) strings is really, really fast. My guess is that set can't beat it. I tried to beat it recently with a binary search function. Even after applying psyco find was still faster (though I could beat the bisect functions by a little bit by replacing a divide with a shift). -- Neil Cerutti This is not a book to be put down lightly. It should be thrown with great force. --Dorothy Parker -- http://mail.python.org/mailman/listinfo/python-list
Re: making a valid file name...
If you're doing it on a time-critical basis, it might help to make valid a set, which should have O(1) membership testing, rather than using the in test with a string. I don't know how well the find() method of a string performs in relationship to in testing of a set. Test and see, if it's important. The find method of (8-bit) strings is really, really fast. My guess is that set can't beat it. I tried to beat it recently with a binary search function. Even after applying psyco find was still faster (though I could beat the bisect functions by a little bit by replacing a divide with a shift). In theory (you know...that little town in west Texas where everything goes right), a set-membership test should be O(1). A binary search function would be O(log N). A linear search of a string for a member should be O(N). In practice, however, for such small strings as the given whitelist, the underlying find() operation likely doesn't put a blip on the radar. If your whitelist were some huge document that you were searching repeatedly, it could have worse performance. Additionally, the find() in the underlying C code is likely about as bare-metal as it gets, whereas the set membership aspect of things may go through some more convoluted setup/teardown/hashing and spend a lot more time further from the processor's op-codes. And I know that a number of folks have done some hefty optimization of Python's string-handling abilities. There's likely a tradeoff point where it's better to use one over the other depending on the size of the whitelist. YMMV -tkc -- http://mail.python.org/mailman/listinfo/python-list
Re: making a valid file name...
On 2006-10-17, Edgar Matzinger [EMAIL PROTECTED] wrote:
Hi,
On 10/17/2006 06:22:45 PM, SpreadTooThin wrote:
valid =
':./,^0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ '
not specifying the OS platform, these are not all the
characters that may occur in a filename: '[]{}-=, etc. And '/'
is NOT valid. On a unix platform. And it should be easy to
scan the filename and check every character against the
'valid-string'.
In the interactive fiction world where I come from, a portable
filename is only 8 chars long and matches the regex
[A-Z][A-Z0-9]*, i.e., capital letters and numbers, with no
extension. That way it'll work on old DOS machines and on
Risc-OS. Wait... is there Python for Risc-OS?
--
Neil Cerutti
HTH, cu l8r, Edgar.
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