How do I converted a null (0) terminated string to a Python string?

[Michael]

Hi All,

I've received (via UDP) a null terminated string and need to convert it
into a Python string. Can anyone tell me how this is done? If it helps,
I know the number of characters in the string.

Thanks,
M. McDonnell

[Steve Holden]

Michael wrote:

Hi All,

I've received (via UDP) a null terminated string and need to convert it
into a Python string. Can anyone tell me how this is done? If it helps,
I know the number of characters in the string.

Thanks,
M. McDonnell

Have you received this string in Python or in C? If the former, then
just throw away the last character of the string you've received and
you're done!

s = s[:-1]

regards
Steve
--
Steve Holden [phone] [phone]
Holden Web LLC/Ltd http://www.holdenweb.com
Skype: holdenweb http://holdenweb.blogspot.com
Recent Ramblings http://del.icio.us/steve.holden

[John Machin]

Michael wrote:

Hi All,

I've received (via UDP) a null terminated string and need to convert it
into a Python string. Can anyone tell me how this is done? If it helps,
I know the number of characters in the string.

I think you mean NUL, not null.

What have you received it into, if it's not a Python string?

You probably need/want this:

if strg[-1] == "\0":
strg = strg[:-1]
alternatively:
strg = strg.rstrip("\0 ") # requires Python 2.2.2 or later

It's possible you may be talking about a fixed length string which
contains useful_stuff + "\0" + padding -- in that case you need

strg = strg.split("\0" )[0] # grab upto (but not including) the first
NUL (if any)

If you're not sure what you've got, print repr(the_input_ string)

HTH,
John

[Michael]

Thank you very much for your responses. To answer some of the
questions... Yes, I am in Python receiving a C language 0 terminated
string that was sent to my Python program in a UDP packet (which is how
I know the count). Are your responses still correct given this
clarification?

Thanks much,
MDM

John Machin wrote:

Michael wrote:

Hi All,

I've received (via UDP) a null terminated string and need to convert it
into a Python string. Can anyone tell me how this is done? If it helps,
I know the number of characters in the string.

I think you mean NUL, not null.

What have you received it into, if it's not a Python string?

You probably need/want this:

if strg[-1] == "\0":
strg = strg[:-1]
alternatively:
strg = strg.rstrip("\0 ") # requires Python 2.2.2 or later

It's possible you may be talking about a fixed length string which
contains useful_stuff + "\0" + padding -- in that case you need

strg = strg.split("\0" )[0] # grab upto (but not including) the first
NUL (if any)

If you're not sure what you've got, print repr(the_input_ string)

HTH,
John

[John Machin]

Michael top-posted [corrected]:

John Machin wrote:

Michael wrote:

Hi All,
>
I've received (via UDP) a null terminated string and need to convert it
into a Python string. Can anyone tell me how this is done? If it helps,
I know the number of characters in the string.
>

I think you mean NUL, not null.

What have you received it into, if it's not a Python string?

You probably need/want this:

if strg[-1] == "\0":
strg = strg[:-1]
alternatively:
strg = strg.rstrip("\0 ") # requires Python 2.2.2 or later

It's possible you may be talking about a fixed length string which
contains useful_stuff + "\0" + padding -- in that case you need

strg = strg.split("\0" )[0] # grab upto (but not including) the first
NUL (if any)

If you're not sure what you've got, print repr(the_input_ string)

HTH,
John

Thank you very much for your responses. To answer some of the
questions... Yes, I am in Python receiving a C language 0 terminated
string that was sent to my Python program in a UDP packet (which is how
I know the count). Are your responses still correct given this
clarification?

My responses are correct. Your "clarificat ion" indicates to me that you
are going by what you are told, not by inspection of (several instances
of) the packet contents, using repr(). It's up to you whether you want
to be skeptical about the packet contents or not. I certainly wouldn't
be throwing the last byte away without checking that it was in fact a
NUL.

Cheers,
John

[Michael]

John,

Thanks for your reply. Just wondering... how are Python strings
formatted? Evidently they're not 0 terminated.

Thanks again,
MDM

John Machin wrote:

Michael top-posted [corrected]:

John Machin wrote:

Michael wrote:
Hi All,

I've received (via UDP) a null terminated string and need to convert it
into a Python string. Can anyone tell me how this is done? If it helps,
I know the number of characters in the string.

>
I think you mean NUL, not null.
>
What have you received it into, if it's not a Python string?
>
You probably need/want this:
>
if strg[-1] == "\0":
strg = strg[:-1]
alternatively:
strg = strg.rstrip("\0 ") # requires Python 2.2.2 or later
>
It's possible you may be talking about a fixed length string which
contains useful_stuff + "\0" + padding -- in that case you need
>
strg = strg.split("\0" )[0] # grab upto (but not including) the first
NUL (if any)
>
If you're not sure what you've got, print repr(the_input_ string)
>
HTH,
John

Thank you very much for your responses. To answer some of the
questions... Yes, I am in Python receiving a C language 0 terminated
string that was sent to my Python program in a UDP packet (which is how
I know the count). Are your responses still correct given this
clarification?

My responses are correct. Your "clarificat ion" indicates to me that you
are going by what you are told, not by inspection of (several instances
of) the packet contents, using repr(). It's up to you whether you want
to be skeptical about the packet contents or not. I certainly wouldn't
be throwing the last byte away without checking that it was in fact a
NUL.

Cheers,
John

[John Machin]

Michael top-posted [again]:

>
John Machin wrote:

Michael top-posted [corrected]:

John Machin wrote:
Michael wrote:
Hi All,
>
I've received (via UDP) a null terminated string and need to convert it
into a Python string. Can anyone tell me how this is done? If it helps,
I know the number of characters in the string.
>

I think you mean NUL, not null.

What have you received it into, if it's not a Python string?

You probably need/want this:

if strg[-1] == "\0":
strg = strg[:-1]
alternatively:
strg = strg.rstrip("\0 ") # requires Python 2.2.2 or later

It's possible you may be talking about a fixed length string which
contains useful_stuff + "\0" + padding -- in that case you need

strg = strg.split("\0" )[0] # grab upto (but not including) the first
NUL (if any)

If you're not sure what you've got, print repr(the_input_ string)

HTH,
John
Thank you very much for your responses. To answer some of the
questions... Yes, I am in Python receiving a C language 0 terminated
string that was sent to my Python program in a UDP packet (which is how
I know the count). Are your responses still correct given this
clarification?

My responses are correct. Your "clarificat ion" indicates to me that you
are going by what you are told, not by inspection of (several instances
of) the packet contents, using repr(). It's up to you whether you want
to be skeptical about the packet contents or not. I certainly wouldn't
be throwing the last byte away without checking that it was in fact a
NUL.

Cheers,
John

John,

Thanks for your reply. Just wondering... how are Python strings
formatted? Evidently they're not 0 terminated.

A Python string is an object. The details of the internal storage may
vary between implementations . CPython has 8-bit str objects and 16-bit
or 32-bit Unicode objects. In IronPython, (str is Unicode) is true, and
they are 16 bits. In any case the object knows its own length without
having to scan for a terminator. Thus, a string can contain NULs.

Having said all that, the CPython str implementation does have an
additional byte at the end; this is set to zero and is not counted in
the length. However you never see that and don't really need to know
unless you are writing an extension module in C -- it's handy to know
that you don't have to append a NUL if you want to call a C library
function.

Cheers,
John

[Fredrik Lundh]

Michael wrote:

Thanks for your reply. Just wondering... how are Python strings
formatted? Evidently they're not 0 terminated.

have you tried *printing* the thing you got via UDP?

to get a programmer-friendly representation of an arbitrary object, use

print repr(obj)

(where obj is your string, in this case).

</F>

[John Machin]

Fredrik Lundh wrote:

Michael wrote:

Thanks for your reply. Just wondering... how are Python strings
formatted? Evidently they're not 0 terminated.

have you tried *printing* the thing you got via UDP?

to get a programmer-friendly representation of an arbitrary object, use

print repr(obj)

(where obj is your string, in this case).

Probably not; there was no indication after the two messages where I
mentioned repr :-)

[Michael]

John,

Since I'm new to Python, I'm having trouble understanding what this
means (see below). Would appreciate any help.

if strg[-1] == "\0":
strg = strg[:-1]

Thanks,
MDM

John Machin wrote:

Fredrik Lundh wrote:

Michael wrote:

Thanks for your reply. Just wondering... how are Python strings
formatted? Evidently they're not 0 terminated.

have you tried *printing* the thing you got via UDP?

to get a programmer-friendly representation of an arbitrary object, use

print repr(obj)

(where obj is your string, in this case).

Probably not; there was no indication after the two messages where I
mentioned repr :-)