R
revuesbio
Hi
Does anyone have the python version of the conversion from msbin to
ieee?
Thank u
Does anyone have the python version of the conversion from msbin to
ieee?
Thank u
Does anyone have the python version of the conversion from msbin to
ieee?
Hi
Does anyone have the python version of the conversion from msbin to
ieee?
Thank u
Yes, Google has it. Google is your friend. Ask Google. It will lead
you to such as:
http://mail.python.org/pipermail/python-list/2005-August/337817.html
HTH,
John
Thank you,
I've already read it but the problem is always present. this script is
for double precision MBF format ( 8 bytes).
I try to adapt this script for single precision MBF format ( 4 bytes)
but i don't find the right float value.
for example : 'P\xad\x02\x95' will return '0.00024924660101532936'
Thank you,I've already read it but the problem is always present. this script is
for double precision MBF format ( 8 bytes).
It would have been somewhat more helpful had you said what you had
done so far, even posted your code ...
I try to adapt this script for single precision MBF format ( 4 bytes)
but i don't find the right float value.for example : 'P\xad\x02\x95' will return '0.00024924660101532936'
If you know what the *correct* value is, you might like to consider
shifting left by log2(correct_value/erroneous_value)
Do you have any known correct pairs of (mbf4 string, decimal_float
value)? My attempt is below -- this is based on a couple of
descriptive sources that my friend Google found, with no test data. I
believe the correct answer for the above input is 1070506.0 i.e. you
are out by a factor of 2 ** 32
def mbf4_as_float(s):
m0, m1, m2, m3 = [ord(c) for c in s]
exponent = m3
if not exponent:
return 0.0
sign = m2 & 0x80
m2 |= 0x80
mant = (((m2 << 8) | m1) << 8) | m0
adj = 24 + 128
num = mant * 2.0 ** (exponent - adj)
if sign:
return -num
return num
HTH,
John
b=bytes[:]from struct import *
x = list(unpack('BBBB','P\xad\x02\x95'))
x [80, 173, 2, 149]
def conversion1(bytes):
It would have been somewhat more helpful had you said what you had
done so far, even posted your code ...If you know what the *correct* value is, you might like to consider
shifting left by log2(correct_value/erroneous_value)Do you have any known correct pairs of (mbf4 string, decimal_float
value)? My attempt is below -- this is based on a couple of
descriptive sources that my friend Google found, with no test data. I
believe the correct answer for the above input is 1070506.0 i.e. you
are out by a factor of 2 ** 32def mbf4_as_float(s):
m0, m1, m2, m3 = [ord(c) for c in s]
exponent = m3
if not exponent:
return 0.0
sign = m2 & 0x80
m2 |= 0x80
mant = (((m2 << 8) | m1) << 8) | m0
adj = 24 + 128
num = mant * 2.0 ** (exponent - adj)
if sign:
return -num
return numHTH,
John
well done ! it's exactly what i'm waiting for !!
my code was:>>> from struct import *x = list(unpack('BBBB','P\xad\x02\x95'))
x [80, 173, 2, 149]
def conversion1(bytes):
b=bytes[:]
sign = bytes[-2] & 0x80
b[-2] |= 0x80
exp = bytes[-1] - 0x80 - 56
acc = 0L
for i,byte in enumerate(b[:-1]):
acc |= (long(byte)<<(i*8))
return (float(acc)*2.0**exp)*((1.,-1.)[sign!=0])
0.00024924660101532936
this script come from google groups but i don't understand bit-string
manipulation (I'm a newbie). informations about bit-string
manipulation with python is too poor on the net.
thank you very much for your script.
Hi
Does anyone have the python version of the conversion from msbin to
ieee?
Thank u
Yes, Google has it. Google is your friend. Ask Google. It will lead
you to such as:
http://mail.python.org/pipermail/python-list/2005-August/337817.html
HTH,
John
Thank you,
I've already read it but the problem is always present. this script is
for double precision MBF format ( 8 bytes).
It would have been somewhat more helpful had you said what you had
done so far, even posted your code ...
I try to adapt this script for single precision MBF format ( 4 bytes)
but i don't find the right float value.
for example : 'P\xad\x02\x95' will return '0.00024924660101532936'
If you know what the *correct* value is, you might like to consider
shifting left by log2(correct_value/erroneous_value)
Do you have any known correct pairs of (mbf4 string, decimal_float
value)? My attempt is below -- this is based on a couple of
descriptive sources that my friend Google found, with no test data. I
believe the correct answer for the above input is 1070506.0 i.e. you
are out by a factor of 2 ** 32
def mbf4_as_float(s):
m0, m1, m2, m3 = [ord(c) for c in s]
exponent = m3
if not exponent:
return 0.0
sign = m2 & 0x80
m2 |= 0x80
mant = (((m2 << 8) | m1) << 8) | m0
adj = 24 + 128
num = mant * 2.0 ** (exponent - adj)
if sign:
return -num
return num
HTH,
Johnwell done ! it's exactly what i'm waiting for !!my code was:>>> from struct import *x = list(unpack('BBBB','P\xad\x02\x95'))
x [80, 173, 2, 149]
def conversion1(bytes):b=bytes[:]
sign = bytes[-2] & 0x80
b[-2] |= 0x80
exp = bytes[-1] - 0x80 - 56
acc = 0L
for i,byte in enumerate(b[:-1]):
acc |= (long(byte)<<(i*8))
return (float(acc)*2.0**exp)*((1.,-1.)[sign!=0])
Apart from the 2**32 problem, the above doesn't handle *any* of the
2**24 different representations of zero. Try feeding \0\0\0\0' to it
and see what you get.
this script come from google groups but i don't understand bit-string
manipulation (I'm a newbie). informations about bit-string
manipulation with python is too poor on the net.
The basic operations (and, or, exclusive-or, shift) are not specific
to any language. Several languages share the same notation (& | ^ <<
thank you very much for your script.
Don't thank me, publish some known correct pairs of values so that we
can verify that it's not just accidentally correct for 1 pair of
values.
Hi
Does anyone have the python version of the conversion from msbin to
ieee?
Thank u
Yes, Google has it. Google is your friend. Ask Google. It will lead
you to such as:
http://mail.python.org/pipermail/python-list/2005-August/337817.html
HTH,
John
Thank you,
I've already read it but the problem is always present. this script is
for double precision MBF format ( 8 bytes).
It would have been somewhat more helpful had you said what you had
done so far, even posted your code ...
I try to adapt this script for single precision MBF format ( 4 bytes)
but i don't find the right float value.
for example : 'P\xad\x02\x95' will return '0.00024924660101532936'
If you know what the *correct* value is, you might like to consider
shifting left by log2(correct_value/erroneous_value)
Do you have any known correct pairs of (mbf4 string, decimal_float
value)? My attempt is below -- this is based on a couple of
descriptive sources that my friend Google found, with no test data. I
believe the correct answer for the above input is 1070506.0 i.e. you
are out by a factor of 2 ** 32
def mbf4_as_float(s):
m0, m1, m2, m3 = [ord(c) for c in s]
exponent = m3
if not exponent:
return 0.0
sign = m2 & 0x80
m2 |= 0x80
mant = (((m2 << 8) | m1) << 8) | m0
adj = 24 + 128
num = mant * 2.0 ** (exponent - adj)
if sign:
return -num
return num
HTH,
John
well done ! it's exactly what i'm waiting for !!
my code was:>>> from struct import *
x = list(unpack('BBBB','P\xad\x02\x95'))
x
[80, 173, 2, 149]
def conversion1(bytes):
b=bytes[:]
sign = bytes[-2] & 0x80
b[-2] |= 0x80
exp = bytes[-1] - 0x80 - 56
acc = 0L
for i,byte in enumerate(b[:-1]):
acc |= (long(byte)<<(i*8))
return (float(acc)*2.0**exp)*((1.,-1.)[sign!=0])Apart from the 2**32 problem, the above doesn't handle *any* of the
2**24 different representations of zero. Try feeding \0\0\0\0' to it
and see what you get.The basic operations (and, or, exclusive-or, shift) are not specific
to any language. Several languages share the same notation (& | ^ <<Don't thank me, publish some known correct pairs of values so that we
can verify that it's not just accidentally correct for 1 pair of
values.
pairs of values :
(bytes string, mbf4_as_float(s) result) right
float value
('P\xad\x02\x95', 1070506.0)
1070506.0
('\x00\x00\x00\x02', 5.8774717541114375e-039) 0.0
('\x00\x00\x00\x81', 1.0)
1.0
('\x00\x00\x00\x82', 2.0)
2.0
('\x00\x00@\x82', 3.0)
3.0
('\x00\x00\x00\x83', 4.0)
4.0
('\x00\x00 \x83', 5.0)
5.0
('\xcd\xcc\x0c\x81', 1.1000000238418579) 1.1
('\xcd\xcc\x0c\x82', 2.2000000476837158) 2.2
('33S\x82', 3.2999999523162842) 3.3
('\xcd\xcc\x0c\x83', 4.4000000953674316) 4.4
['4', '4.4', '4.40', '4.400', '4.4000', '4.40000', '4.400000',['%.*f' % (decplaces, 4.4000000953674316) for decplaces in range(10)]
Hi
Does anyone have the python version of the conversion from msbin to
ieee?
Thank u
Yes, Google has it. Google is your friend. Ask Google. It will lead
you to such as:
http://mail.python.org/pipermail/python-list/2005-August/337817.html
HTH,
John
Thank you,
I've already read it but the problem is always present. this script is
for double precision MBF format ( 8 bytes).
It would have been somewhat more helpful had you said what you had
done so far, even posted your code ...
I try to adapt this script for single precision MBF format ( 4 bytes)
but i don't find the right float value.
for example : 'P\xad\x02\x95' will return '0.00024924660101532936'
If you know what the *correct* value is, you might like to consider
shifting left by log2(correct_value/erroneous_value)
Do you have any known correct pairs of (mbf4 string, decimal_float
value)? My attempt is below -- this is based on a couple of
descriptive sources that my friend Google found, with no test data. I
believe the correct answer for the above input is 1070506.0 i.e. you
are out by a factor of 2 ** 32
def mbf4_as_float(s):
m0, m1, m2, m3 = [ord(c) for c in s]
exponent = m3
if not exponent:
return 0.0
sign = m2 & 0x80
m2 |= 0x80
mant = (((m2 << 8) | m1) << 8) | m0
adj = 24 + 128
num = mant * 2.0 ** (exponent - adj)
if sign:
return -num
return num
HTH,
John
well done ! it's exactly what i'm waiting for !!
my code was:>>> from struct import *
x = list(unpack('BBBB','P\xad\x02\x95'))
x
[80, 173, 2, 149]
def conversion1(bytes):
b=bytes[:]
sign = bytes[-2] & 0x80
b[-2] |= 0x80
exp = bytes[-1] - 0x80 - 56
acc = 0L
for i,byte in enumerate(b[:-1]):
acc |= (long(byte)<<(i*8))
return (float(acc)*2.0**exp)*((1.,-1.)[sign!=0])
Apart from the 2**32 problem, the above doesn't handle *any* of the
2**24 different representations of zero. Try feeding \0\0\0\0' to it
and see what you get.
conversion1(x)
0.00024924660101532936
this script come from google groups but i don't understand bit-string
manipulation (I'm a newbie). informations about bit-string
manipulation with python is too poor on the net.
The basic operations (and, or, exclusive-or, shift) are not specific
to any language. Several languages share the same notation (& | ^ <<
), having inherited it from C.
thank you very much for your script.
Don't thank me, publish some known correct pairs of values so that we
can verify that it's not just accidentally correct for 1 pair of
values.pairs of values :
(bytes string, mbf4_as_float(s) result) right
float value
('P\xad\x02\x95', 1070506.0)
1070506.0
('\x00\x00\x00\x02', 5.8774717541114375e-039) 0.0
There is no way that \x00\x00\x00\x02' could represent exactly zero.
What makes you think it does? Rounding?
('\x00\x00\x00\x81', 1.0)
1.0
('\x00\x00\x00\x82', 2.0)
2.0
('\x00\x00@\x82', 3.0)
3.0
('\x00\x00\x00\x83', 4.0)
4.0
('\x00\x00 \x83', 5.0)
5.0
('\xcd\xcc\x0c\x81', 1.1000000238418579) 1.1
('\xcd\xcc\x0c\x82', 2.2000000476837158) 2.2
('33S\x82', 3.2999999523162842) 3.3
('\xcd\xcc\x0c\x83', 4.4000000953674316) 4.4
It is not apparent whether you regard the output from the function as
correct or not.
4.4 "converted" to mbf4 format is '\xcd\xcc\x0c\x83' which is
4.4000000953674316 which is the closest possible mbf4 representation
of 4.4 (difference is 9.5e-008).
The next lower mbf4 value '\xcc\xcc\x0c\x83' is 4.3999996185302734
(difference is -3.8e-007).
Note that floating-point representation of many decimal fractions is
inherently inexact. print repr(4.4) produces 4.4000000000000004
Have you read this:
http://docs.python.org/tut/node16.html
?
If you need decimal-fraction output that matches what somebody typed
into the original software, or saw on the screen, you will need to
know/guess the precision that was involved, and round the numbers
accordingly -- just like the author of the original software would
have needed to do.
['%.*f' % (decplaces, 4.4000000953674316) for decplaces in range(10)]
['4', '4.4', '4.40', '4.400', '4.4000', '4.40000', '4.400000',
'4.4000001', '4.40000010', '4.400000095']
HTH,
John
Hi
Does anyone have the python version of the conversion from msbin to
ieee?
Thank u
Yes, Google has it. Google is your friend. Ask Google. It will lead
you to such as:
http://mail.python.org/pipermail/python-list/2005-August/337817.html
HTH,
John
Thank you,
I've already read it but the problem is always present. this script is
for double precision MBF format ( 8 bytes).
It would have been somewhat more helpful had you said what you had
done so far, even posted your code ...
I try to adapt this script for single precision MBF format ( 4 bytes)
but i don't find the right float value.
for example : 'P\xad\x02\x95' will return '0.00024924660101532936'
If you know what the *correct* value is, you might like to consider
shifting left by log2(correct_value/erroneous_value)
Do you have any known correct pairs of (mbf4 string, decimal_float
value)? My attempt is below -- this is based on a couple of
descriptive sources that my friend Google found, with no test data. I
believe the correct answer for the above input is 1070506.0 i.e. you
are out by a factor of 2 ** 32
def mbf4_as_float(s):
m0, m1, m2, m3 = [ord(c) for c in s]
exponent = m3
if not exponent:
return 0.0
sign = m2 & 0x80
m2 |= 0x80
mant = (((m2 << 8) | m1) << 8) | m0
adj = 24 + 128
num = mant * 2.0 ** (exponent - adj)
if sign:
return -num
return num
HTH,
John
well done ! it's exactly what i'm waiting for !!
my code was:>>> from struct import *
x = list(unpack('BBBB','P\xad\x02\x95'))
x
[80, 173, 2, 149]
def conversion1(bytes):
b=bytes[:]
sign = bytes[-2] & 0x80
b[-2] |= 0x80
exp = bytes[-1] - 0x80 - 56
acc = 0L
for i,byte in enumerate(b[:-1]):
acc |= (long(byte)<<(i*8))
return (float(acc)*2.0**exp)*((1.,-1.)[sign!=0])
Apart from the 2**32 problem, the above doesn't handle *any* of the
2**24 different representations of zero. Try feeding \0\0\0\0' to it
and see what you get.
conversion1(x)
0.00024924660101532936
this script come from google groups but i don't understand bit-string
manipulation (I'm a newbie). informations about bit-string
manipulation with python is too poor on the net.
The basic operations (and, or, exclusive-or, shift) are not specific
to any language. Several languages share the same notation (& | ^ <<
), having inherited it from C.
thank you very much for your script.
Don't thank me, publish some known correct pairs of values so that we
can verify that it's not just accidentally correct for 1 pair of
values.
pairs of values :
(bytes string, mbf4_as_float(s) result) right
float value
('P\xad\x02\x95', 1070506.0)
1070506.0
('\x00\x00\x00\x02', 5.8774717541114375e-039) 0.0There is no way that \x00\x00\x00\x02' could represent exactly zero.
What makes you think it does? Rounding?It is not apparent whether you regard the output from the function as
correct or not.4.4 "converted" to mbf4 format is '\xcd\xcc\x0c\x83' which is
4.4000000953674316 which is the closest possible mbf4 representation
of 4.4 (difference is 9.5e-008).The next lower mbf4 value '\xcc\xcc\x0c\x83' is 4.3999996185302734
(difference is -3.8e-007).Note that floating-point representation of many decimal fractions is
inherently inexact. print repr(4.4) produces 4.4000000000000004If you need decimal-fraction output that matches what somebody typed
into the original software, or saw on the screen, you will need to
know/guess the precision that was involved, and round the numbers
accordingly -- just like the author of the original software would
have needed to do.['%.*f' % (decplaces, 4.4000000953674316) for decplaces in range(10)]['4', '4.4', '4.40', '4.400', '4.4000', '4.40000', '4.400000',
'4.4000001', '4.40000010', '4.400000095']HTH,
John
another couples and round number corresponding to the right value
('\x00\x00\x00\x02', 5.8774717541114375e-039, '0.000') [snip]
all is ok.
thank u
Hi
Does anyone have the python version of the conversion from msbin to
ieee?
Thank u
Not sure if this helps, but I think this thread has the answer;http://groups.google.com/group/comp.lang.python/browse_thread/thread/...
Check out the response from Bengt Richter. His function did the right
thing.
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