Hi,
I was wondering how I ought to be handling character range
translations in python.

What I want to do is translate fullwidth numbers and roman alphabet
characters into their halfwidth ascii equivalents.
In perl I can do this pretty easily with tr:

tr/\x{ff00}-\x{ff5e}/\x{0020}-\x{007e}/;

and I think the string.translate method is what I need to use to
achieve the equivalent in python. Unfortunately the maktrans method
doesn't seem to accept character ranges and I'm also having trouble
with it's interpretation of length. What I came up with was to first
fudge the ranges:

my_test_string = u"$B#A#B#C#D#E#F#G(B"
f_range = "".join([unichr(x) for x in
range(ord(u"\uff00"),ord(u"\uff5e"))])
t_range = "".join([unichr(x) for x in
range(ord(u"\u0020"),ord(u"\u007e"))])

then use these as input to maketrans:
my_trans_string =
my_test_string.translate(string.maketrans(f_range, t_range))
Traceback (most recent call last):
File "<stdin>", line 1, in ?
UnicodeEncodeError: 'ascii' codec can't encode characters in position
0-93: ordinal not in range(128)

but it generates an encoding error... and if I encodethe ranges in
utf8 before passing them on I get a length error because maketrans is
counting bytes not characters and utf8 is variable width...
my_trans_string =
my_test_string.translate(string.maketrans(f_range. encode("utf8"),t_range.encode("utf8")))
Traceback (most recent call last):
File "<stdin>", line 1, in ?
ValueError: maketrans arguments must have same length

On Aug 13, 5:18 pm, kettle <Josef.Robert.No...@gmail.comwrote:

Hi,
I was wondering how I ought to be handling character range
translations in python.
>
What I want to do is translate fullwidth numbers and roman alphabet
characters into their halfwidth ascii equivalents.
In perl I can do this pretty easily with tr:
>
tr/\x{ff00}-\x{ff5e}/\x{0020}-\x{007e}/;
>
and I think the string.translate method is what I need to use to
achieve the equivalent in python. Unfortunately the maktrans method
doesn't seem to accept character ranges and I'm also having trouble
with it's interpretation of length. What I came up with was to first
fudge the ranges:
>
my_test_string = u"$B#A#B#C#D#E#F#G(B"
f_range = "".join([unichr(x) for x in
range(ord(u"\uff00"),ord(u"\uff5e"))])
t_range = "".join([unichr(x) for x in
range(ord(u"\u0020"),ord(u"\u007e"))])
>
then use these as input to maketrans:
my_trans_string =
my_test_string.translate(string.maketrans(f_range, t_range))
Traceback (most recent call last):
File "<stdin>", line 1, in ?
UnicodeEncodeError: 'ascii' codec can't encode characters in position
0-93: ordinal not in range(128)
>
but it generates an encoding error... and if I encodethe ranges in
utf8 before passing them on I get a length error because maketrans is
counting bytes not characters and utf8 is variable width...
my_trans_string =
my_test_string.translate(string.maketrans(f_range. encode("utf8"),t_range.encode("utf8")))
Traceback (most recent call last):
File "<stdin>", line 1, in ?
ValueError: maketrans arguments must have same length

Ok so I guess I was barking up the wrong tree. Searching for python $BA43Q(B
$B!!H>3Q(B quickly brought up a solution:

$B%U%,%[%2(B-%*@ABC-%*@123

still, it would be nice if there was a more general solution, or if
maketrans actually looked at chars instead of bytes methinks.

kettle wrote:

I was wondering how I ought to be handling character range
translations in python.
>
What I want to do is translate fullwidth numbers and roman alphabet
characters into their halfwidth ascii equivalents.
In perl I can do this pretty easily with tr:
>
tr/\x{ff00}-\x{ff5e}/\x{0020}-\x{007e}/;
>
and I think the string.translate method is what I need to use to
achieve the equivalent in python. Unfortunately the maktrans method
doesn't seem to accept character ranges and I'm also having trouble
with it's interpretation of length. What I came up with was to first
fudge the ranges:
>
my_test_string = u"$B#A#B#C#D#E#F#G(B"
f_range = "".join([unichr(x) for x in
range(ord(u"\uff00"),ord(u"\uff5e"))])
t_range = "".join([unichr(x) for x in
range(ord(u"\u0020"),ord(u"\u007e"))])
>
then use these as input to maketrans:
my_trans_string =
my_test_string.translate(string.maketrans(f_range, t_range))
Traceback (most recent call last):
File "<stdin>", line 1, in ?
UnicodeEncodeError: 'ascii' codec can't encode characters in position
0-93: ordinal not in range(128)

maketrans only works for byte strings.

as for translate itself, it has different signatures for byte strings
and unicode strings; in the former case, it takes lookup table
represented as a 256-byte string (e.g. created by maketrans), in the
latter case, it takes a dictionary mapping from ordinals to ordinals or
unicode strings.

something like

lut = dict((0xff00 + ch, 0x0020 + ch) for ch in range(0x80))

new_string = old_string.translate(lut)

could work (untested).

</F>

On Aug 13, 5:33 pm, Fredrik Lundh <fred...@pythonware.comwrote:

kettle wrote:

>

>

>

>

>

>
maketrans only works for byte strings.
>
as for translate itself, it has different signatures for byte strings
and unicode strings; in the former case, it takes lookup table
represented as a 256-byte string (e.g. created by maketrans), in the
latter case, it takes a dictionary mapping from ordinals to ordinals or
unicode strings.
>
something like
>
lut = dict((0xff00 + ch, 0x0020 + ch) for ch in range(0x80))
>
new_string = old_string.translate(lut)
>
could work (untested).
>
</F>

excellent. i didnt realize from the docs that i could do that. thanks