Re: eval('07') works, eval('08') fails, why?
On 2009-01-09, Dennis Lee Bieber wlfr...@ix.netcom.com wrote: On Thu, 08 Jan 2009 09:46:26 -0600, Grant Edwards inva...@invalid declaimed the following in comp.lang.python: Heathkit Z80 stuff used octal notation too. Octal worked well for the old 8080 and derivative processors as there were only 7 registers and memory/indirect to encode in an instruction... So (pseudo example) a MOV command might have been 01sssddd (binary) or 1SD (octal) and S or D representing A 1 B 2 C 3 D 4 E 5 H 6 L 7 Mem 0 (indirect via contents of HL pair) I presume that's why DEC chose octal for the PDP-11 also. There were 8 registers and 8 addressing modes, so they ended up with several fields within the opcodes that were three-bits wide and aligned with octal digits: http://en.wikipedia.org/wiki/PDP-11#Instruction_set When I was in University, we spent an entire quarter studying the PDP-11 instruction set at the binary/octal level and discussing instruction decoding and sequencing. We wrote a few PDP-11 assembly language programs as well, but the course was more about machine level instruction sets than about assembly language. Octal made a lot of sense if you had to deal with raw memory, but once you had access to an assembler and disassembler it didn't really matter. -- Grant Edwards grante Yow! NANCY!! Why is at everything RED?! visi.com -- http://mail.python.org/mailman/listinfo/python-list
Re: eval('07') works, eval('08') fails, why?
Hi,
07 is octal. That's way 08 is invalid. Try this:
=== python
print 011
9
print int('011')
11
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Thomas Guettler, http://www.thomas-guettler.de/
E-Mail: guettli (*) thomas-guettler + de
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Re: eval('07') works, eval('08') fails, why?
On Jan 8, 9:31 am, Alex van der Spek am...@xs4all.nl wrote:
eval('07')
7
eval('08')
Traceback (most recent call last):
File pyshell#3, line 1, in module
eval('08')
File string, line 1
08
^
SyntaxError: invalid token
An integer literal with a leading zero is
interpreted as an octal (base 8) number,
so only digits in the range 0-7 (inclusive)
are permitted in such a literal.
Mark
I can't think of anything that could cause this. Similarly, eval('09')
fails, but for string 0x with x8 it works. I am teaching myself Python
in order to climb the ladder from
Algol(1980s)--Pascal(1990s)--VisualBasic(2000)--Python. I am a physicist,
have programmed computers
all my life but I won't understand the real tech jargon of present day
computer science. Please keep it simple
Thanks in advance,
Alex van der Spek
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Re: eval('07') works, eval('08') fails, why?
On 2009-01-08, Alex van der Spek am...@xs4all.nl wrote: Thanks much, that makes sense! Well, that's the correct explanation. Whether that feature makes sense or not is debatable. Even I'm not old-school enough that I ever use octal literals -- and I used Unix on a PDP-11 for years (actually had my own PDP-11 for while, but it never worked). Now that I think of it, my Heathkit Z80 stuff used octal notation too. -- Grant Edwards grante Yow! I represent a at sardine!! visi.com -- http://mail.python.org/mailman/listinfo/python-list
Re: eval('07') works, eval('08') fails, why?
Thanks much, that makes sense! Alex van der Spek -- http://mail.python.org/mailman/listinfo/python-list
Re: eval('07') works, eval('08') fails, why?
In article hnwdnzhtdblpgvvunz2dnuvz_vzin...@posted.visi, Unknown unkn...@unknown.invalid wrote: On 2009-01-08, Alex van der Spek am...@xs4all.nl wrote: Thanks much, that makes sense! Well, that's the correct explanation. Whether that feature makes sense or not is debatable. The debate is over! In Py 3.0, octal literals changed from 07 to 0o7; the old format gets an 'invalid token' parsing error. -- Ned Deily, n...@acm.org -- http://mail.python.org/mailman/listinfo/python-list
Re: eval('07') works, eval('08') fails, why?
Alex van der Spek wrote:
I can't think of anything that could cause this. Similarly, eval('09')
fails, but for string 0x with x8 it works. I am teaching myself Python
in order to climb the ladder from Algol(1980s)--Pascal(1990s)--
VisualBasic(2000)--Python. I am a physicist, have programmed computers
all my life but I won't understand the real tech jargon of present day
computer science. Please keep it simple
I taught myself Python as a statistician with a Fortran/C backgound by
interleaving interactive experiments (such as you did) with reading of
the manuals. The Language Manual chapter on Lexical Analysis has an
Integer Literals subsection that answers this question. I strongly
recommend you peruse the Language Manual and the initial Library Manual
chapters on built-ins.
tjr
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Re: eval('07') works, eval('08') fails, why?
Grant Edwards a écrit : On 2009-01-08, Alex van der Spek am...@xs4all.nl wrote: Thanks much, that makes sense! Well, that's the correct explanation. Whether that feature makes sense or not is debatable. Even I'm not old-school enough that I ever use octal literals -- and I used Unix on a PDP-11 for years (actually had my own PDP-11 for while, but it never worked). Now that I think of it, my Heathkit Z80 stuff used octal notation too. What about your DeathStation 9000 ?-) -- http://mail.python.org/mailman/listinfo/python-list
Re: eval('07') works, eval('08') fails, why?
On 2009-01-08, Bruno Desthuilliers bdesth.quelquech...@free.quelquepart.fr wrote: Grant Edwards a ?crit : On 2009-01-08, Alex van der Spek am...@xs4all.nl wrote: Thanks much, that makes sense! Well, that's the correct explanation. Whether that feature makes sense or not is debatable. Even I'm not old-school enough that I ever use octal literals -- and I used Unix on a PDP-11 for years (actually had my own PDP-11 for while, but it never worked). Now that I think of it, my Heathkit Z80 stuff used octal notation too. What about your DeathStation 9000 ?-) The closest thing I've seen to a DS9K would probably be a CDC Cyber 6600 mainframe. I guess for somebody with a mainframe background it might not have been too weird, but for somebody who came from a PDP-11, Z80, 65XX background, it seemed awfully obtuse. -- Grant Edwards grante Yow! I'm having a RELIGIOUS at EXPERIENCE ... and I don't visi.comtake any DRUGS -- http://mail.python.org/mailman/listinfo/python-list
