Micro-PEP: str.translate(N one) to mean identity translation

[Bengt Richter]

Just thought None as the first argument would be both handy and mnemonic,
signifying no translation, but allowing easy expression of deleting characters,
e.g.,

s = s.translate(Non e, 'badcharshere')

Regards,
Bengt Richter

[Michael Spencer]

Bengt Richter wrote:

Just thought None as the first argument would be both handy and mnemonic,
signifying no translation, but allowing easy expression of deleting characters,
e.g.,

s = s.translate(Non e, 'badcharshere')

Regards,
Bengt Richter

+1

Michael

[M.E.Farmer]

Bengt Richter wrote:

Just thought None as the first argument would be both handy and mnemonic, signifying no translation, but allowing easy expression of deleting characters, e.g.,

s = s.translate(Non e, 'badcharshere')

Regards,
Bengt Richter

What's wrong with :

s = s.replace('badc hars', "")

It seems obvious to replace a char ( to me anyway ) with a blank
string, rather than to 'translate' it to None.
I am sure you have a reason what am I missing ?
M.E.Farmer

[Bengt Richter]

On 29 Apr 2005 21:27:18 -0700, "M.E.Farmer " <me*****@hotmai l.com> wrote:

Bengt Richter wrote:

Just thought None as the first argument would be both handy andmnemonic,

signifying no translation, but allowing easy expression of deleting

characters,

e.g.,

s = s.translate(Non e, 'badcharshere')

Regards,
Bengt Richter

What's wrong with :

s = s.replace('badc hars', "")

That's not what translate does with the badchars, which is a set of
characters, each and all of whose instances in the source string
will be deleted from the source string. Something like
for c in badchars:
s = s.replace(c,'')
It seems obvious to replace a char ( to me anyway ) with a blank
string, rather than to 'translate' it to None.
I am sure you have a reason what am I missing ?
M.E.Farmer

The first argument is normally a 256-character string that serves as a table
for converting source characters to destination, so s.translate(tab le, bad)
does something like
s = ''.join([table[ord(c)] for c in s if c not in bad]

help(str.transl ate) Help on method_descript or:

translate(...)
S.translate(tab le [,deletechars]) -> string
Return a copy of the string S, where all characters occurring
in the optional argument deletechars are removed, and the
remaining characters have been mapped through the given
translation table, which must be a string of length 256.

So just to delete, you wind up constructinf a table argument that is just 1:1 as in
'abcde'.transla te(''.join([chr(i) for i in xrange(256)]), 'tbd')

'ace'

and the answer to the question, "What translation does such a table do?" is "None" ;-)

Regards,
Bengt Richter

[Peter Otten]

M.E.Farmer wrote:

Bengt Richter wrote:

Just thought None as the first argument would be both handy and

mnemonic,

signifying no translation, but allowing easy expression of deleting

characters,

e.g.,

s = s.translate(Non e, 'badcharshere')

Regards,
Bengt Richter

What's wrong with :

s = s.replace('badc hars', "")

It seems obvious to replace a char ( to me anyway ) with a blank
string, rather than to 'translate' it to None.
I am sure you have a reason what am I missing ?
M.E.Farmer

s = "NHoBwA RyAoSuB AsAeHeH AiBtH,A CnRoAwD HyBoAuC HdRoCnH'AtB"
s.translate(Non e, "BADCHARS") "Now you see it, now you don't" s.replace("BADC HARS", "") "NHoBwA RyAoSuB AsAeHeH AiBtH,A CnRoAwD HyBoAuC HdRoCnH'AtB"

i. e. you have to replace() for every char in "BADCHARS":
reduce(lambda x, y: x.replace(y, ""), "BADCHARS", s)

"Now you see it, now you don't"
+1, btw.

Peter

[Raymond Hettinger]

[Bengt Richter]

Just thought None as the first argument would be both handy and mnemonic,
signifying no translation, but allowing easy expression of deleting characters, e.g.,

s = s.translate(Non e, 'badcharshere')

Log a feature request on SF and assignment to me.
I'll put this in for you.
Raymond Hettinger

[M.E.Farmer]

After I re-read your post in daylight and read your followup the "Aha!"
hit me .I am a little slow at times. I have always just iterated thru
the badchars and replaced with "" . What you suggest would be very
nice indeed!
Thanks for the time and explanation, and you too Peter !

For what it is worth +1 ;)

On another note why is maketrans in the string module....
I was a bit lost finding it the first time should it be builtin?
transtable = "abcdefg".maket rans("qwertyu")
Probably missing something.
M.E.Farmer

[Bengt Richter]

On Sat, 30 Apr 2005 08:44:21 GMT, "Raymond Hettinger" <vz******@veriz on.net> wrote:

[Bengt Richter]

Just thought None as the first argument would be both handy and mnemonic,
signifying no translation, but allowing easy expression of deleting

characters,

e.g.,

s = s.translate(Non e, 'badcharshere')

Log a feature request on SF and assignment to me.
I'll put this in for you.

Thanks. It has request ID # 1193128

Regards,
Bengt Richter