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Why does the "".join(r) do this?

Hello,

I'm getting an error join-ing strings and wonder if someone can
explain why the function is behaving this way? If I .join in a string
that contains a high character then I get an ascii codec decoding
error. (The code below illustrates.) Why doesn't it just
concatenate?

I'm building up a web page by stuffing an array and then doing
"".join(r) at
the end. I intend to later encode it as 'latin1', so I'd like it to
just concatenate. While I can work around this error, the reason for
it escapes me.

Thanks,
Jim

=============== == program: try.py
#!/usr/bin/python2.3 -u
t="abc"+chr(174 )+"def"
print(u"next: %s :there" % (t.decode('lati n1'),))
print t
r=["x",'y',u'z ']
r.append(t)
k="".join(r)
print k

=============== === command line (on my screen between the first abc
and def is
a circle-R, while between the second two is a black oval with a
white
question mark, in case anyone cares):
jim@joshua:~$ ./try.py
next: abc®def :there
abc�def
Traceback (most recent call last):
File "./try.py", line 7, in ?
k="".join(r)
UnicodeDecodeEr ror: 'ascii' codec can't decode byte 0xae in position
3: ordinal not in range(128)
Jul 18 '05 #1
16 2437
Jim Hefferon wrote:
I'm getting an error join-ing strings and wonder if someone can
explain why the function is behaving this way? If I .join in a string
that contains a high character then I get an ascii codec decoding
error. (The code below illustrates.) Why doesn't it just
concatenate?


It can't just concatenate because your list contains other
items which are unicode strings. Python is attempting to convert
your strings to unicode strings to do the join, and it fails
because your strings contain characters which don't have
meaning to the default decoder.

-Peter
Jul 18 '05 #2

Jim> I'm building up a web page by stuffing an array and then doing
Jim> "".join(r) at the end. I intend to later encode it as 'latin1', so
Jim> I'd like it to just concatenate. While I can work around this
Jim> error, the reason for it escapes me.

Try

u"".join(r)

instead. I think the join operation is trying to convert the Unicode bits
in your list of strings to strings by encoding using the default codec,
which appears to be ASCII.

Skip

Jul 18 '05 #3
Jim Hefferon wrote:
I'm getting an error join-ing strings and wonder if someone can
explain why the function is behaving this way? If I .join in a string
that contains a high character then I get an ascii codec decoding
error. (The code below illustrates.) Why doesn't it just
concatenate?


Let's reduce the problem to its simplest case:
unichr(174) + chr(174) Traceback (most recent call last):
File "<stdin>", line 1, in ?
UnicodeDecodeEr ror: 'ascii' codec can't decode byte 0xae in position 0:
ordinal not in range(128)

So why doesn't it just concatenate? Because there is no way of knowing how
to properly decode chr(174) or any other non-ascii character to unicode:
chr(174).decode ("latin1") u'\xae' chr(174).decode ("latin2") u'\u017d'


Use either unicode or str, but don't mix them. That should keep you out of
trouble.

Peter

Jul 18 '05 #4
Skip Montanaro wrote:
Try

u"".join(r)

instead. I think the join operation is trying to convert the Unicode bits
in your list of strings to strings by encoding using the default codec,
which appears to be ASCII.


This is bound to fail when the first non-ascii str occurs:
u"".join(["a", "b"]) u'ab' u"".join(["a", chr(174)]) Traceback (most recent call last):
File "<stdin>", line 1, in ?
UnicodeDecodeEr ror: 'ascii' codec can't decode byte 0xae in position 0:
ordinal not in range(128)
Apart from that, Python automatically switches to unicode if the list
contains unicode items:
"".join(["a", u"o"])

u'ao'

Peter

Jul 18 '05 #5
Jim Hefferon wrote:
Hello,

I'm getting an error join-ing strings and wonder if someone can
explain why the function is behaving this way? If I .join in a string
that contains a high character then I get an ascii codec decoding
error. (The code below illustrates.) Why doesn't it just
concatenate?

I'm building up a web page by stuffing an array and then doing
"".join(r) at
the end. I intend to later encode it as 'latin1', so I'd like it to
just concatenate. While I can work around this error, the reason for
it escapes me.

Thanks,
Jim

=============== == program: try.py
#!/usr/bin/python2.3 -u
t="abc"+chr(174 )+"def"
print(u"next: %s :there" % (t.decode('lati n1'),))
print t
r=["x",'y',u'z ']
r.append(t)
k="".join(r)
print k

=============== === command line (on my screen between the first abc
and def is
a circle-R, while between the second two is a black oval with a
white
question mark, in case anyone cares):
jim@joshua:~$ ./try.py
next: abc®def :there
abc�def
Traceback (most recent call last):
File "./try.py", line 7, in ?
k="".join(r)
UnicodeDecodeEr ror: 'ascii' codec can't decode byte 0xae in position
3: ordinal not in range(128)


What about unichr() ?
#!/usr/bin/python2.3 -u
t="abc"+unichr( 174)+"def"
print t
print(u"next: %s :there" % (t),)
print t
r=["x",'y',u'z ']
r.append(t)
k="".join(r)
print k



Jul 18 '05 #6
Jim Hefferon wrote:
Hello,

I'm getting an error join-ing strings and wonder if someone can
explain why the function is behaving this way? If I .join in a string
that contains a high character then I get an ascii codec decoding
error. (The code below illustrates.) Why doesn't it just
concatenate?

I'm building up a web page by stuffing an array and then doing
"".join(r) at
the end. I intend to later encode it as 'latin1', so I'd like it to
just concatenate. While I can work around this error, the reason for
it escapes me.

Thanks,
Jim

=============== == program: try.py
#!/usr/bin/python2.3 -u
t="abc"+chr(174 )+"def"
print(u"next: %s :there" % (t.decode('lati n1'),))
print t
r=["x",'y',u'z ']
r.append(t)
k="".join(r)
print k

=============== === command line (on my screen between the first abc
and def is
a circle-R, while between the second two is a black oval with a
white
question mark, in case anyone cares):
jim@joshua:~$ ./try.py
next: abc®def :there
abc�def
Traceback (most recent call last):
File "./try.py", line 7, in ?
k="".join(r)
UnicodeDecodeEr ror: 'ascii' codec can't decode byte 0xae in position
3: ordinal not in range(128)


What about unichr() ?
#!/usr/bin/python2.3 -u
t="abc"+unichr( 174)+"def"
print t
print(u"next: %s :there" % (t),)
print t
r=["x",'y',u'z ']
r.append(t)
# k=u"".join(r)
k="".join(r)
print k
// moma
http://www.futuredesktop.org
Jul 18 '05 #7

Peter> Skip Montanaro wrote:
Try

u"".join(r)

instead. I think the join operation is trying to convert the Unicode bits
in your list of strings to strings by encoding using the default codec,
which appears to be ASCII.


Peter> This is bound to fail when the first non-ascii str occurs:

...

Yeah I realized that later. I missed that he was appending non-ASCII
strings to his list. I thought he was only appending unicode objects and
ASCII strings (in which case what he was trying should have worked). Serves
me right for trying to respond with a head cold.

Skip

Jul 18 '05 #8
Peter Otten wrote:
Skip Montanaro wrote:

Try

u"".join(r)

instead. I think the join operation is trying to convert the Unicode bits
in your list of strings to strings by encoding using the default codec,
which appears to be ASCII.

This is bound to fail when the first non-ascii str occurs:


Is there a way to change the default codec in a part of a program?
(Meaning that different parts of program deal with strings they know are
in a specific different code pages?)
--
C isn't that hard: void (*(*f[])())() defines f as an array of
unspecified size, of pointers to functions that return pointers to
functions that return void.
Jul 18 '05 #9
"Ivan Voras" <ivoras@__geri. cc.fer.hr> wrote in message
news:c8******** **@bagan.srce.h r...
Peter Otten wrote:
Skip Montanaro wrote:

Try

u"".join(r)

instead. I think the join operation is trying to convert the Unicode bitsin your list of strings to strings by encoding using the default codec,
which appears to be ASCII.

This is bound to fail when the first non-ascii str occurs:


Is there a way to change the default codec in a part of a program?
(Meaning that different parts of program deal with strings they know are
in a specific different code pages?)


Does the encoding line (1st or second line of program) do this?
I don't remember if it does or not - although I'd suspect not.
Otherwise it seems like a reasonably straightforward function
to write.

John Roth

--
C isn't that hard: void (*(*f[])())() defines f as an array of
unspecified size, of pointers to functions that return pointers to
functions that return void.

Jul 18 '05 #10

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