Base conversion method or module

[Jeff Wagner]

Is there a Python module or method that can convert between numeric bases? Specifically, I need to
convert between Hex, Decimal and Binary such as 5Ah = 90d = 01011010b.

I searched many places but couldn't find a Python specific one.

Thanks, Jeff

[Francis Avila]

Jeff Wagner wrote in message <0b************ *************** *****@4ax.com>. ..

Is there a Python module or method that can convert between numeric bases? Specifically, I need toconvert between Hex, Decimal and Binary such as 5Ah = 90d = 01011010b.

I searched many places but couldn't find a Python specific one.

Thanks, Jeff

There was a Python cookbook recipe that did these kinds of conversions,
IIRC. Look around at http://aspn.activestate.com/ASPN/Cookbook/Python.
Numeric might do this sort of thing, too, but I don't know.

Python itself can get you pretty far; the problem is that it's a bit spotty
in making conversions communicable.

For example, int() and long() both accept a string with a base argument, so
you can convert just about any base (2 <= base <= 36) to a Python int or
long.

Python can also go the other way around, taking a number and converting to a
string representation of the bases you want. The problem? There's only a
function to do this for hex and oct, not for bin or any of the other bases
int can handle.

Ideally, there's be a do-it-all function that is the inverse of int(): take
a number and spit out a string representation in any base (2-36) you want.

But the binary case is pretty simple:

def bin(number):
"""bin(numb er) -> string

Return the binary representation of an integer or long integer.

"""
if number == 0: return '0b0'
binrep = []
while number >0:
binrep.append(n umber&1)
number >>= 1
binrep.reverse( )
return '0b'+''.join(ma p(str,binrep))
Dealing with negative ints is an exercise for the reader....

Remember also that Python has hex and octal literals.
--
Francis Avila

[Jeff Wagner]

On Sun, 7 Dec 2003 15:45:41 -0500, "Francis Avila" <fr***********@ yahoo.com> wrotf:

Jeff Wagner wrote in message <0b************ *************** *****@4ax.com>. ..

Is there a Python module or method that can convert between numeric bases?

Specifically , I need to

convert between Hex, Decimal and Binary such as 5Ah = 90d = 01011010b.

I searched many places but couldn't find a Python specific one.

Thanks, Jeff

There was a Python cookbook recipe that did these kinds of conversions,
IIRC. Look around at http://aspn.activestate.com/ASPN/Cookbook/Python.
Numeric might do this sort of thing, too, but I don't know.

Python itself can get you pretty far; the problem is that it's a bit spotty
in making conversions communicable.

For example, int() and long() both accept a string with a base argument, so
you can convert just about any base (2 <= base <= 36) to a Python int or
long.

Python can also go the other way around, taking a number and converting to a
string representation of the bases you want. The problem? There's only a
function to do this for hex and oct, not for bin or any of the other bases
int can handle.

Ideally, there's be a do-it-all function that is the inverse of int(): take
a number and spit out a string representation in any base (2-36) you want.

But the binary case is pretty simple:

def bin(number):
"""bin(numb er) -> string

Return the binary representation of an integer or long integer.

"""
if number == 0: return '0b0'
binrep = []
while number >0:
binrep.append(n umber&1)
number >>= 1
binrep.reverse( )
return '0b'+''.join(ma p(str,binrep))
Dealing with negative ints is an exercise for the reader....

Remember also that Python has hex and octal literals.

Francis,

I found the Python cookbook recipe you were referring to. It is as follows:

The module name is BaseConvert.py .......

#!/usr/bin/env python

BASE2 = "01"
BASE10 = "0123456789 "
BASE16 = "0123456789ABCD EF"
BASE62 = "ABCDEFGHIJKLMN OPQRSTUVWXYZ012 3456789abcdefgh ijklmnopqrstuvw xyz"

def convert(number, fromdigits,todi gits):

if str(number)[0]=='-':
number = str(number)[1:]
neg=1
else:
neg=0

# make an integer out of the number
x=long(0)
for digit in str(number):
x = x*len(fromdigit s) + fromdigits.inde x(digit)

# create the result in base 'len(todigits)'
res=""
while x>0:
digit = x % len(todigits)
res = todigits[digit] + res
x /= len(todigits)
if neg:
res = "-"+res

return res

I am getting an error when I import this module and call it.

#!/usr/bin/python

import BaseConvert
print BaseConvert.con vert(90,BASE10, BASE2)

Name Error: name 'Base10' is not defined.

This probably has something to do with namespaces which was biting me a while ago. I thought that
since the 'Base' definitions were global to this module (BaseConvert.py ) by being defined outside
the function (convert), that when I imported this module, they would be global, too.

From one of my books, it says, "An import statement creates a new namespace that contains all the
attributes of the module. To access an attribute in this namespace, use the name of the module
object as a prefix: import MyModule ... a = MyModule.f( )" which is what I thought I was
doing.

What am I still missing?

Thanks,
Jeff

[Fredrik Lundh]

Jeff Wagner wrote:

I found the Python cookbook recipe you were referring to. It is as follows:
(what's wrong with just posting an URL?)
I am getting an error when I import this module and call it.

#!/usr/bin/python

import BaseConvert
print BaseConvert.con vert(90,BASE10, BASE2)

Name Error: name 'Base10' is not defined.

This probably has something to do with namespaces which was biting me
a while ago. I thought that since the 'Base' definitions were global to this
module (BaseConvert.py ) by being defined outside the function (convert),
that when I imported this module, they would be global, too.
in Python, "global" means "belonging to a module", not "visible in all
modules in my entire program"
What am I still missing?

change the call to use BaseConvert.BAS E10 and BaseConvert.BAS E2

to learn more about local and global names, read this:

http://www.python.org/doc/current/ref/naming.html

</F>

[Jeff Wagner]

On Mon, 8 Dec 2003 00:40:46 +0100, "Fredrik Lundh" <fr*****@python ware.com> wrotf:

Jeff Wagner wrote:

I found the Python cookbook recipe you were referring to. It is as follows:

(what's wrong with just posting an URL?)

What a great idea ;) ...
http://aspn.activestate.com/ASPN/Coo.../Recipe/111286

I am getting an error when I import this module and call it.

#!/usr/bin/python

import BaseConvert
print BaseConvert.con vert(90,BASE10, BASE2)

Name Error: name 'Base10' is not defined.

This probably has something to do with namespaces which was biting me
a while ago. I thought that since the 'Base' definitions were global to this
module (BaseConvert.py ) by being defined outside the function (convert),
that when I imported this module, they would be global, too.

in Python, "global" means "belonging to a module", not "visible in all
modules in my entire program"

What am I still missing?

change the call to use BaseConvert.BAS E10 and BaseConvert.BAS E2

to learn more about local and global names, read this:

http://www.python.org/doc/current/ref/naming.html

</F>

Thanks,
Jeff

[John Roth]

"Jeff Wagner" <JW*****@hotmai l.com> wrote in message
news:ji******** *************** *********@4ax.c om...

On Sun, 7 Dec 2003 15:45:41 -0500, "Francis Avila" <fr***********@ yahoo.com> wrotf:

I am getting an error when I import this module and call it.

#!/usr/bin/python

import BaseConvert
print BaseConvert.con vert(90,BASE10, BASE2)

Name Error: name 'Base10' is not defined.

This probably has something to do with namespaces which was biting me a while ago. I thought that since the 'Base' definitions were global to this module (BaseConvert.py ) by being defined outside the function (convert), that when I imported this module, they would be global, too.
From one of my books, it says, "An import statement creates a new namespace that contains all the attributes of the module. To access an attribute in this namespace, use the name of the module object as a prefix: import MyModule ... a = MyModule.f( )" which is what I thought I was doing.

What am I still missing?
print BaseConvert.con vert(90, BaseConvert.BAS E10, BaseConvert.BAS E2)

John Roth
Thanks,
Jeff

[Francis Avila]

Jeff Wagner wrote in message ...

On Mon, 8 Dec 2003 00:40:46 +0100, "Fredrik Lundh" <fr*****@python ware.com> wrotf:

Jeff Wagner wrote:

I found the Python cookbook recipe you were referring to. It is as

follows:
(what's wrong with just posting an URL?)

What a great idea ;) ...
http://aspn.activestate.com/ASPN/Coo.../Recipe/111286

Hey, I found another one which is the more general "inverse of int/long"
function I was pining for (and thus learning for the n-th time that one
should check the cookbook first before reinventing the wheel):

http://aspn.activestate.com/ASPN/Coo.../Recipe/222109

For some reason it's in the "Text" category, and uses the term "radix,"
which is less common than "base".

Hettinger's version (found in the discussion below) is better.

Shouldn't something like this get into the builtins, so we can get rid of
hex/oct in Python3k?
--
Francis Avila

[Mensanator]

>Subject: Re: Base conversion method or module

From: "Francis Avila" fr***********@y ahoo.com
Date: 12/7/2003 8:52 PM Central Standard Time
Message-id: <vt************ @corp.supernews .com>
Jeff Wagner wrote in message ...

On Mon, 8 Dec 2003 00:40:46 +0100, "Fredrik Lundh" <fr*****@python ware.com>wrotf:

Jeff Wagner wrote:

I found the Python cookbook recipe you were referring to. It is asfollows:
(what's wrong with just posting an URL?)

What a great idea ;) ...
http://aspn.activestate.com/ASPN/Coo.../Recipe/111286

Hey, I found another one which is the more general "inverse of int/long"
function I was pining for (and thus learning for the n-th time that one
should check the cookbook first before reinventing the wheel):

http://aspn.activestate.com/ASPN/Coo.../Recipe/222109

These are nice, but they're very slow:

For i=2**177149 - 1

224.797000051 sec for baseconvert
202.733999968 sec for dec2bin (my routine)
137.735000014 sec for radix

Compare those to the .digits function that is part of GMPY

0.59399998188 sec

That can make quite a difference when you're running through a couple million
iterations.


For some reason it's in the "Text" category, and uses the term "radix,"
which is less common than "base".

Hettinger's version (found in the discussion below) is better.

Shouldn't something like this get into the builtins, so we can get rid of
hex/oct in Python3k?
--
Francis Avila

--
Mensanator
Ace of Clubs

[Jeff Wagner]

On Sun, 7 Dec 2003 21:52:23 -0500, "Francis Avila" <fr***********@ yahoo.com> wrotf:

Jeff Wagner wrote in message ...

On Mon, 8 Dec 2003 00:40:46 +0100, "Fredrik Lundh" <fr*****@python ware.com>

wrotf:

Jeff Wagner wrote:

I found the Python cookbook recipe you were referring to. It is asfollows:
(what's wrong with just posting an URL?)

What a great idea ;) ...
http://aspn.activestate.com/ASPN/Coo.../Recipe/111286

Hey, I found another one which is the more general "inverse of int/long"
function I was pining for (and thus learning for the n-th time that one
should check the cookbook first before reinventing the wheel):

http://aspn.activestate.com/ASPN/Coo.../Recipe/222109

For some reason it's in the "Text" category, and uses the term "radix,"
which is less common than "base".

Hettinger's version (found in the discussion below) is better.

Shouldn't something like this get into the builtins, so we can get rid of
hex/oct in Python3k?

Thanks Francis, this is excellent! I think I just made a major breakthrough. It's all starting to
come together. I'm sure something will stump me again, though (and it's going to be Classes when I
get there ;)

Jeff

[Jeff Wagner]

On 08 Dec 2003 04:45:17 GMT, me********@aol. compost (Mensanator) wrotf:

Subject: Re: Base conversion method or module
From: "Francis Avila" fr***********@y ahoo.com
Date: 12/7/2003 8:52 PM Central Standard Time
Message-id: <vt************ @corp.supernews .com>
Jeff Wagner wrote in message ...

On Mon, 8 Dec 2003 00:40:46 +0100, "Fredrik Lundh" <fr*****@python ware.com>

wrotf:

Jeff Wagner wrote:

> I found the Python cookbook recipe you were referring to. It is as

follows:

(what's wrong with just posting an URL?)

What a great idea ;) ...
http://aspn.activestate.com/ASPN/Coo.../Recipe/111286

Hey, I found another one which is the more general "inverse of int/long"
function I was pining for (and thus learning for the n-th time that one
should check the cookbook first before reinventing the wheel):

http://aspn.activestate.com/ASPN/Coo.../Recipe/222109

These are nice, but they're very slow:

For i=2**177149 - 1

224.79700005 1 sec for baseconvert
202.73399996 8 sec for dec2bin (my routine)
137.73500001 4 sec for radix

Compare those to the .digits function that is part of GMPY

0.5939999818 8 sec

That can make quite a difference when you're running through a couple million
iterations.

So I decide to go and try out this GMPY and download the win32 binaries. It consists of two files,
gmpy.pyd and pysymbolicext.p yd ... what do I do with them, just copy them to the lib folder?

Then it says I need GMP-4.x so I get that, too. It's like nothing I've ever seen before. How can I
install that on my WinXP box?

Thanks, Jeff