Re: [Tutor] Removing control characters
"Kent Johnson" wrote in message
news:1c2a2c590902191500y71600feerff0b73a88fb49...@mail.gmail.com...
On Thu, Feb 19, 2009 at 5:41 PM, Dinesh B Vadhia
wrote:
Okay, here is a combination of Mark's suggestions and yours:
# replace unwanted chars in string s with " "
t = "".join([(" " if n in c else n) for n in s if n not in c])
t
'Product ConceptsHard candy with an innovative twist, Internet Archive:
Wayback Machine. [online] Mar. 25, 2004. Retrieved from the Internet
http://www.confectionery-innovations.com>.'
This last bit doesn't work ie. replacing the unwanted chars with " " -
eg.
'ConceptsHard'. What's missing?
The "if n not in c" at the end of the list comp rejects the unwanted
characters from the result immediately. What you wrote is the same as
t = "".join([n for n in s if n not in c])
because "n in c" will never be true in the first conditional.
BTW if you care about performance, this is the wrong approach. At
least use a set for c; better would be to use translate().
Sorry, I didn't catch the "replace with space" part. Kent is right,
translate is what you want. The join is still nice for making the
translation table:
table = ''.join(' ' if n < 32 or n > 126 else chr(n) for n in
xrange(256))
string.translate('here is\x01my\xffstring',table)
'here is my string'
-Mark
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Re: [Tutor] Removing control characters
On Thu, Feb 19, 2009 at 5:41 PM, Dinesh B Vadhia
wrote:
> Okay, here is a combination of Mark's suggestions and yours:
>> # replace unwanted chars in string s with " "
>> t = "".join([(" " if n in c else n) for n in s if n not in c])
>> t
> 'Product ConceptsHard candy with an innovative twist, Internet Archive:
> Wayback Machine. [online] Mar. 25, 2004. Retrieved from the Internet http://www.confectionery-innovations.com>.'
>
> This last bit doesn't work ie. replacing the unwanted chars with " " - eg.
> 'ConceptsHard'. What's missing?
The "if n not in c" at the end of the list comp rejects the unwanted
characters from the result immediately. What you wrote is the same as
t = "".join([n for n in s if n not in c])
because "n in c" will never be true in the first conditional.
BTW if you care about performance, this is the wrong approach. At
least use a set for c; better would be to use translate().
Kent
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Re: [Tutor] Removing control characters
Okay, here is a combination of Mark's suggestions and yours:
> # string of all chars
> a = ''.join([chr(n) for n in range(256)])
> a
'\x00\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f
!"#$%&\'()*+,-./0123456789:;<=>?...@abcdefghijklmnopqrstuvwxyz[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\x7f\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f\x90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf\xb0\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf\xd0\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf\xe0\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff'
> # string of wanted chars
> b = ''.join([n for n in a if ord(n) >= 32 and ord(n) <= 126])
> b
'
!"#$%&\'()*+,-./0123456789:;<=>?...@abcdefghijklmnopqrstuvwxyz[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~'
> # string of unwanted chars > ord(126)
> c = ''.join([n for n in a if ord(n) < 32 or ord(n) > 126])
> c
'\x00\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f\x7f\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f\x90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf\xb0\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf\xd0\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf\xe0\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff'
> # the string to process
> s = "Product Concepts\xe2\x80\x94Hard candy with an innovative twist,
> Internet Archive: Wayback Machine. [online] Mar. 25, 2004. Retrieved from the
> Internet http://www.confectionery-innovations.com>."
> # replace unwanted chars in string s with " "
> t = "".join([(" " if n in c else n) for n in s if n not in c])
> t
'Product ConceptsHard candy with an innovative twist, Internet Archive: Wayback
Machine. [online] Mar. 25, 2004. Retrieved from the Internet http://www.confectionery-innovations.com>.'
This last bit doesn't work ie. replacing the unwanted chars with " " - eg.
'ConceptsHard'. What's missing?
Dinesh
From: Kent Johnson
Sent: Thursday, February 19, 2009 12:36 PM
To: Dinesh B Vadhia
Cc: tutor@python.org
Subject: Re: [Tutor] Removing control characters
On Thu, Feb 19, 2009 at 2:25 PM, Dinesh B Vadhia
wrote:
> # 3) Replacing a set of characters with a single character ie.
>
> for c in str:
> if c in set:
> string.replace (c, r)
>
> to give
>
>> 'Chris Perkins : $$$-'
> My solution is:
>
> print ''.join[string.replace(c, r) for c in str if c in set]
With the syntax corrected this will not do what you want; the "if c in
set" filters the characters in the result, so the result will contain
only the replacement characters. You would need something like
''.join([ (r if c in set else c) for c in str])
Note that both 'set' and 'str' are built-in names and therefore poor
choices for variable names.
Kent
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Re: [Tutor] Removing control characters
On Thu, Feb 19, 2009 at 2:25 PM, Dinesh B Vadhia wrote: > # 3) Replacing a set of characters with a single character ie. > > for c in str: > if c in set: > string.replace (c, r) > > to give > >> 'Chris Perkins : $$$-' > My solution is: > > print ''.join[string.replace(c, r) for c in str if c in set] With the syntax corrected this will not do what you want; the "if c in set" filters the characters in the result, so the result will contain only the replacement characters. You would need something like ''.join([ (r if c in set else c) for c in str]) Note that both 'set' and 'str' are built-in names and therefore poor choices for variable names. Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Removing control characters
On Thu, Feb 19, 2009 at 11:25 AM, Dinesh B Vadhia wrote: > My solution is: > > print ''.join[string.replace(c, r) for c in str if c in set] > > But, this returns a syntax error. Any idea why? > Probably because you didn't use parentheses - join() is a function. -- www.fsrtechnologies.com ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Removing control characters
At the bottom of the link http://code.activestate.com/recipes/303342/ there are list comprehensions for string manipulation ie. import string str = 'Chris Perkins : 224-7992' set = '0123456789' r = '$' # 1) Keeping only a given set of characters. print ''.join([c for c in str if c in set]) > '2247992' # 2) Deleting a given set of characters. print ''.join([c for c in str if c not in set]) > 'Chris Perkins : -' The missing one is # 3) Replacing a set of characters with a single character ie. for c in str: if c in set: string.replace (c, r) to give > 'Chris Perkins : $$$-' My solution is: print ''.join[string.replace(c, r) for c in str if c in set] But, this returns a syntax error. Any idea why? Ta! Dinesh From: Kent Johnson Sent: Thursday, February 19, 2009 8:03 AM To: Dinesh B Vadhia Cc: tutor@python.org Subject: Re: [Tutor] Removing control characters On Thu, Feb 19, 2009 at 10:14 AM, Dinesh B Vadhia wrote: > I want a regex to remove control characters (< chr(32) and > chr(126)) from > strings ie. > > line = re.sub(r"[^a-z0-9-';.]", " ", line) # replace all chars NOT A-Z, > a-z, 0-9, [-';.] with " " > > 1. What is the best way to include all the required chars rather than list > them all within the r"" ? You have to list either the chars you want, as you have done, or the ones you don't want. You could use r'[\x00-\x1f\x7f-\xff]' or r'[^\x20-\x7e]' > 2. How do you handle the inclusion of the quotation mark " ? Use \", that works even in a raw string. By the way string.translate() is likely to be faster for this purpose than re.sub(). This recipe might help: http://code.activestate.com/recipes/303342/ Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Removing control characters
A regex isn't always the best solution:
>>> a=''.join(chr(n) for n in range(256))
>>> a
'\x00\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f
!"#$%&\'()*+,-./0123456789:;<=>?...@abcdefghijklmnopqrstuvwxyz[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\x7f\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f\x90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf\xb0\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf\xd0\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf\xe0\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff'
>>> b=''.join(n for n in a if ord(n) >= 32 and ord(n) <= 126)
>>> b
'
!"#$%&\'()*+,-./0123456789:;<=>?...@abcdefghijklmnopqrstuvwxyz[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~'
-Mark
"Dinesh B Vadhia" wrote in message
news:col103-ds55714842811febeb4a97ca3...@phx.gbl...
I want a regex to remove control characters (< chr(32) and > chr(126)) from
strings ie.
line = re.sub(r"[^a-z0-9-';.]", " ", line) # replace all chars NOT A-Z,
a-z, 0-9, [-';.] with " "
1. What is the best way to include all the required chars rather than list
them all within the r"" ?
2. How do you handle the inclusion of the quotation mark " ?
Cheers
Dinesh
--
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Re: [Tutor] Removing control characters
On Thu, Feb 19, 2009 at 10:14 AM, Dinesh B Vadhia wrote: > I want a regex to remove control characters (< chr(32) and > chr(126)) from > strings ie. > > line = re.sub(r"[^a-z0-9-';.]", " ", line) # replace all chars NOT A-Z, > a-z, 0-9, [-';.] with " " > > 1. What is the best way to include all the required chars rather than list > them all within the r"" ? You have to list either the chars you want, as you have done, or the ones you don't want. You could use r'[\x00-\x1f\x7f-\xff]' or r'[^\x20-\x7e]' > 2. How do you handle the inclusion of the quotation mark " ? Use \", that works even in a raw string. By the way string.translate() is likely to be faster for this purpose than re.sub(). This recipe might help: http://code.activestate.com/recipes/303342/ Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
