Can string formatting be used to convert an integer to its binaryform ?

[fdu.xiaojf@gmail.com]

Hi,

String formatting can be used to converting an integer to its octal or
hexadecimal form:

>>a = 199
>>"%o" % a

'307'

>>"%x" % a

'c7'

But, can string formatting be used to convert an integer to its binary
form ?


Thanks in advance.

xiaojf

[flupke]

Re: Can string formatting be used to convert an integer to its binaryform ?

fdu.xiaojf@gmai l.com schreef:

Hi,
>
String formatting can be used to converting an integer to its octal or
hexadecimal form:

>>>a = 199
>>>"%o" % a

'307'

>>>"%x" % a

'c7'
>
But, can string formatting be used to convert an integer to its binary
form ?
>
>
Thanks in advance.
>
xiaojf

I don't actually know how to do it with string formatting but you can
create a simple function to do it.
Here's an example:

http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/219300

Regards,
Benedict

[Mirco Wahab]

Re: Can string formatting be used to convert an integer to its binaryform ?

Thus spoke fdu.xiaojf@gmai l.com (on 2006-09-28 09:10):

String formatting can be used to converting an integer to its octal or
hexadecimal form:

>>a = 199
>>"%o" % a

'307'

>>"%x" % a

'c7'
>
But, can string formatting be used to convert an integer to its binary
form ?

I didn't fell over this problem so far but
I *would* have expected to find something
like a 'pack' operator (as in Perl).

And voilá, there is (even basically identical to Perl):

from struct import *

a = 199
a_bin_str = pack('L', a)



Regards

Mirco

[Gabriel Genellina]

Re: Can string formatting be used to convert an integer to itsbinary form ?

At Thursday 28/9/2006 05:22, Mirco Wahab wrote:

String formatting can be used to converting an integer to its octal or
hexadecimal form:

>>a = 199
>>"%o" % a

'307'

>>"%x" % a

'c7'

But, can string formatting be used to convert an integer to its binary
form ?

>
a = 199
a_bin_str = pack('L', a)

Notice that the OP was looking for another thing, given the examples.
Perhaps a better wording would have been "how to convert an integer
to its base-2 string representation" .


Gabriel Genellina
Softlab SRL





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Todo lo que querías saber, y lo que ni imaginabas,
está en Yahoo! Respuestas (Beta).
¡Probalo ya!

http://www.yahoo.com.ar/respuestas

[Mirco Wahab]

Re: Can string formatting be used to convert an integer to its binaryform ?

Thus spoke Gabriel Genellina (on 2006-09-28 11:05):

At Thursday 28/9/2006 05:22, Mirco Wahab wrote:

But, can string formatting be used to convert an integer to its binary
form ?

>>
> a = 199
> a_bin_str = pack('L', a)

>
Notice that the OP was looking for another thing, given the examples.
Perhaps a better wording would have been "how to convert an integer
to its base-2 string representation" .

Yes, you are right. The OP looks for a
'binary (bit) representation ..."
I admit I didn't find out how to format
a value into a bit string in Python.

In Perl, this would be a no-brainer:

$var = 199;
$str = sprintf "%0*b", 32, $var;

and str would contain 000000000000000 000000000110001 11
on a intel machine.

But where is the %b in Python?

Regards & Thanks

Mirco

[bearophileHUGS@lycos.com]

Re: Can string formatting be used to convert an integer to its binary form ?

Mirco Wahab:

But where is the %b in Python?

Python doesn't have that. You can convert the number to a hex, and then
map the hex digitds to binary strings using a dictionary, like this:

http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/440528

Bye,
bearophile

[Frederic Rentsch]

Re: Can string formatting be used to convert an integer to its binaryform ?

bearophileHUGS@ lycos.com wrote:

Mirco Wahab:
>

>But where is the %b in Python?
>>

>
Python doesn't have that. You can convert the number to a hex, and then
map the hex digitds to binary strings using a dictionary, like this:

http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/440528

>
Bye,
bearophile
>
>

Good idea, but shorter with ->

http://cheeseshop.python.org/pypi/SE/2.2%20beta

>>import SE
>>Int_To_Bina ry = SE.SE (SE.SE ('0=0000 1=0001 2=0010 3=0011 4=0100

5=0101 6=0110 7=0111 8=1000 9=1001 A=1010 a=1010 B=1011 b=1011 C=1100
c=1100 D=1101 d=1101 E=1110 e=1110 F=1111 f=1111')

>>Int_To_Bina ry ('%x' % 1234567890')

'01001001100101 100000001011010 010'

>>Int_To_Binary .save ('se_definition _files/int_to_binary.s e')

>>SE.SE ('se_definition _files/int_to_binary.s e') ('%X' % 987654321)

'00111010110111 100110100010110 001'


Frederic

[Mirco Wahab]

Re: Can string formatting be used to convert an integer to its binaryform ?

Thus spoke Frederic Rentsch (on 2006-09-28 20:43):

bearophileHUGS@ lycos.com wrote:

>Mirco Wahab:
>>

>>But where is the %b in Python?

>>
>Python doesn't have that. ...
>http://aspn.activestate.com/ASPN/Coo.../Recipe/440528

>
Good idea, but shorter with ->

http://cheeseshop.python.org/pypi/SE/2.2%20beta

SE.SE ('se_definition _files/int_to_binary.s e') ('%X' % 987654321)
'00111010110111 100110100010110 001'

I don't really understand here:

- why doesn't have Python such a simple and useful thing as to_binstr(...)
even C++ has one built in,
#include <iostream>
#include <bitset>

int somefunc()
{
int val = 199;
std::cout << std::bitset<32> ( val );
...

- why would you favor such complicated solutions
for this (as posted), when you can have this
in one line, e.g.:

def int2bin(num, width=32):
return ''.join(['%c'%(ord('0')+ bool((1<<k)&num )) for k in range((width-1),-1,-1)])

(including a string with specifier,this is what I came up with after
looking up some Python docs - maybe you can straighten this a bit ...)

-- but my goggles might be biased,
I don't really emphasize the "Python way" ;-)

Regards and thanks

Mirco

[Marc 'BlackJack' Rintsch]

Re: Can string formatting be used to convert an integer to its binary form ?

In <efhdt1$9a1$1@m lucom4.urz.uni-halle.de>, Mirco Wahab wrote:

Thus spoke Frederic Rentsch (on 2006-09-28 20:43):

>bearophileHUGS@ lycos.com wrote:

>>Mirco Wahab:
>>>
>>>But where is the %b in Python?
>>>
>>Python doesn't have that. ...
>>http://aspn.activestate.com/ASPN/Coo.../Recipe/440528

>>
>Good idea, but shorter with ->
>http://cheeseshop.python.org/pypi/SE/2.2%20beta
>SE.SE ('se_definition _files/int_to_binary.s e') ('%X' % 987654321)
>'0011101011011 110011010001011 0001'

>
I don't really understand here:
>
- why doesn't have Python such a simple and useful thing as to_binstr(...)

Maybe simple, but useful? And if you really need this it's simple to
implement or look up in the cook book.

- why would you favor such complicated solutions
for this (as posted), when you can have this
in one line, e.g.:
>
def int2bin(num, width=32):
return ''.join(['%c'%(ord('0')+ bool((1<<k)&num )) for k in range((width-1),-1,-1)])

Yeah, I wonder why not everybody sees the beauty in this cool and
straightforward one liner. ;-)

Ciao,
Marc 'BlackJack' Rintsch

[Fredrik Lundh]

Re: Can string formatting be used to convert an integer to its binaryform ?

Mirco Wahab wrote:

- why doesn't have Python such a simple and useful thing as to_binstr(...)

useful? really? for what?

</F>

[Mirco Wahab]

Re: Can string formatting be used to convert an integer to its binaryform ?

Thus spoke Marc 'BlackJack' Rintsch (on 2006-09-28 23:38):

> def int2bin(num, width=32):
> return ''.join(['%c'%(ord('0')+ bool((1<<k)&num )) for k in range((width-1),-1,-1)])

>
Yeah, I wonder why not everybody sees the beauty in this cool and
straightforward one liner. ;-)

Right. I see this is BS, maybe lots of these lines exist already,
one could come up with (sorted by obfuscation, descending):

def int2bin(num, width=32):
# return ''.join( [chr(ord('0')+bo ol(1<<k & num))for k in range(width-1,-1,-1)] )
# return ''.join( map(lambda k:str(num>>k & 1),range(width-1, -1, -1)) )
# return ''.join( [str(num>>k & 1)for k in range(width-1, -1, -1)] )

But after some thinking, I thought about discussing this one:

def i2b(num, width):
return str(1 & num>>(width-1)) + i2b(num, width-1) if width else ''

which is the shortest ;-)

(Sorry but I'm more or less a newbie, maybe this is BS too ...)

Regards

Mirco

[Mirco Wahab]

Re: Can string formatting be used to convert an integer to its binaryform ?

Thus spoke Fredrik Lundh (on 2006-09-28 23:35):

Mirco Wahab wrote:
>

>- why doesn't have Python such a simple and useful thing as to_binstr(...)

>
useful? really? for what?

I don't really know, but according to google,
people often ask exactly for that and there
is no reason at all why one shouldn't expect
to get a /bit string/ from "%b" %.

So if people think it's badly needed, how
couldn't it be *not* useful then? ;-)

It feels to me (as it does sometimes
when diving into Python, to be honest)
simply as a shortcoming, - and the ter-
nary operator included in 2.5 was
imho a huge step forward, next will
be mutable strings and arrays will be
'called arrays' somewhere ... ;-)

(maybe somebody reverses the -v/-V switch too, hey)

Regards

Mirco

[bearophileHUGS@lycos.com]

Re: Can string formatting be used to convert an integer to its binary form ?

Frederic Rentsch:

Good idea, but shorter with ->

>>SE.SE ('se_definition _files/int_to_binary.s e') ('%X' % 987654321)

'00111010110111 100110100010110 001'

Note that your version keeps the leading zeros.
Have you tested the relative speeds too?
(I'll probably have to learn to use SE.)

Bye,
bearophile

[Lawrence D'Oliveiro]

Re: Can string formatting be used to convert an integer to its binary form ?

In message <1159455615.546 936.83170@m7g20 00cwm.googlegro ups.com>, bearophileHUGS@ lycos.com wrote:

Mirco Wahab:

>But where is the %b in Python?

>
Python doesn't have that. You can convert the number to a hex, and then
map the hex digitds to binary strings using a dictionary, like this:
http://aspn.activestate.com/ASPN/Coo.../Recipe/440528

How about this: (where n is the integer you want to convert):

"".join([["0", "1"][(1 << i & n) != 0] for i in range(int(math. ceil(math.log(n , 2))) - 1, -1, -1)])

[Lawrence D'Oliveiro]

Re: Can string formatting be used to convert an integer to its binary form ?

In message <efhril$nrm$1@l ust.ihug.co.nz> , I wrote:

"".join([["0", "1"][(1 << i & n) != 0] for i in range(int(math. ceil(math.log(n , 2))) - 1, -1, -1)])

Uh, make that

"".join([["0", "1"][(1 << i & n) != 0] for i in range(int(math. floor(math.log( n, 2))), -1, -1)])

Need to check those corner cases. :)