parsing engineering symbols

[Suresh Jeevanandam]

Hi,
I want to convert a string to float value. The string contains
engineering symbols.
For example,

s = '12k'

I want some function which would return 12000
function(s)
=> 12000.0
I searched the web, but could not find any function.

regards,
Suresh

[Larry Bates]

Something like:

def cvt(input):
if input.lower().endswith('k'): return float(input[:-1])*1000

[gene tani]

Suresh Jeevanandam wrote:

Hi,
I want to convert a string to float value. The string contains
engineering symbols.
For example,

s = '12k'

I want some function which would return 12000
function(s)
=> 12000.0
I searched the web, but could not find any function.

regards,
Suresh

port this
http://api.rubyonrails.com/classes/A...ric/Bytes.html

[Bengt Richter]

On Tue, 20 Dec 2005 19:07:02 +0530, Suresh Jeevanandam <jm*******@gmail.com> wrote:

Hi,
I want to convert a string to float value. The string contains
engineering symbols.
For example,

s = '12k'

I want some function which would return 12000
function(s)
=> 12000.0
I searched the web, but could not find any function.

It should be easy enough, if you can define precisely what
"contains engineering symbols" means ;-)

Regards,
Bengt Richter

[Erik Max Francis]

Suresh Jeevanandam wrote:

I want to convert a string to float value. The string contains
engineering symbols.
For example,

s = '12k'

I want some function which would return 12000
function(s)
=> 12000.0
I searched the web, but could not find any function.

There's some extensive code in the SI class in BOTEC which does this:

http://www.alcyone.com/software/botec/

--
Erik Max Francis && ma*@alcyone.com && http://www.alcyone.com/max/
San Jose, CA, USA && 37 20 N 121 53 W && AIM erikmaxfrancis
Chance favors the trained mind.
-- Louis Pasteur

[Fredrik Lundh]

Suresh Jeevanandam wrote:

I want to convert a string to float value. The string contains
engineering symbols.

For example,

s = '12k'

I want some function which would return 12000
function(s)
=> 12000.0
I searched the web, but could not find any function.

how about:

SI_prefixes = {
'Y':24, 'Z':21, 'E':18, 'P':15, 'T':12, 'G':9, 'M':6, 'k':3,
'h':2, 'd':-1, 'c':-2, 'm':-3, u'\xb5':-6, 'u':-6, 'n':-9, 'p':-12,
'f':-15, 'a':-18, 'z':-21, 'y':-24
}

def myfloat(str):
try:
exp = SI_prefixes[str[-1]]
return float(str[:-1]) * 10**exp
except KeyError:
return float(str)

?

</F>

[Suresh Jeevanandam]

Exactly what I wanted.

It would be nice if the standard float function takes care of these.

regards,
Suresh

how about:

SI_prefixes = {
'Y':24, 'Z':21, 'E':18, 'P':15, 'T':12, 'G':9, 'M':6, 'k':3,
'h':2, 'd':-1, 'c':-2, 'm':-3, u'\xb5':-6, 'u':-6, 'n':-9, 'p':-12,
'f':-15, 'a':-18, 'z':-21, 'y':-24
}

def myfloat(str):
try:
exp = SI_prefixes[str[-1]]
return float(str[:-1]) * 10**exp
except KeyError:
return float(str)

?

</F>

[Bengt Richter]

On Tue, 20 Dec 2005 23:28:12 +0100, "Fredrik Lundh" <fr*****@pythonware.com> wrote:

Suresh Jeevanandam wrote:

I want to convert a string to float value. The string contains
engineering symbols.

For example,

s = '12k'

I want some function which would return 12000
function(s)
=> 12000.0
I searched the web, but could not find any function.

how about:

SI_prefixes = {
'Y':24, 'Z':21, 'E':18, 'P':15, 'T':12, 'G':9, 'M':6, 'k':3,
'h':2, 'd':-1, 'c':-2, 'm':-3, u'\xb5':-6, 'u':-6, 'n':-9, 'p':-12,
'f':-15, 'a':-18, 'z':-21, 'y':-24
}

def myfloat(str):
try:
exp = SI_prefixes[str[-1]]
return float(str[:-1]) * 10**exp
except KeyError:
return float(str)

?

Nit: why not move 10** out of myfloat into SI_prefixes
(i.e., just retrieve precalculated factors)?

Nit_2: No twinge of conscience shadowing str? ;-)

Regards,
Bengt Richter

[Dave Hansen]

On Wed, 21 Dec 2005 19:10:21 +0530 in comp.lang.python, Suresh
Jeevanandam <jm*******@gmail.com> wrote:

[re: SI prefixes]

Exactly what I wanted.

It would be nice if the standard float function takes care of these.

No, it wouldn't.

Regards,
-=Dave

--
Change is inevitable, progress is not.

[Fredrik Lundh]

Bengt Richter wrote:

Nit: why not move 10** out of myfloat into SI_prefixes
(i.e., just retrieve precalculated factors)?
the table I cut and pasted from only listed the exponents. if you want
to prefix 1e to all the constants, be my guest.
Nit_2: No twinge of conscience shadowing str? ;-)

not the slightest.

</F>

[Jacob Rael]

Just a newbie, trolling.

I like this solution. Simple, easy to understand.

Did you put the SI_prefixes outside the def so you could wrap the
whole thing in a module and reuse it in other blocks?

jr

[Peter Hansen]

Jacob Rael wrote:

Just a newbie, trolling.

I like this solution. Simple, easy to understand.

Did you put the SI_prefixes outside the def so you could wrap the
whole thing in a module and reuse it in other blocks?

Do "import dis" and then try "dis.dis(myfloat)" on Fredrik's version and
on your suggested variation... (Hint, it's likely more an instinct for
decent performance instead of an instinct for decent portability, though
it would serve both purposes.)

-Peter

[Jacob Rael]

Wow!! 261 v. 75 lines!!

jr

[Fredrik Lundh]

Peter Hansen wrote:

Did you put the SI_prefixes outside the def so you could wrap the
whole thing in a module and reuse it in other blocks?

Do "import dis" and then try "dis.dis(myfloat)" on Fredrik's version and
on your suggested variation... (Hint, it's likely more an instinct for
decent performance instead of an instinct for decent portability

I frankly don't see what "portability" has to do with this. Why would the
location of a reusable static data structure matter ? Python code work
the same way in scripts and modules...

</F>

[Peter Hansen]

Fredrik Lundh wrote:

Peter Hansen wrote:

[the OP wrote]

Did you put the SI_prefixes outside the def so you could wrap the
whole thing in a module and reuse it in other blocks?

Do "import dis" and then try "dis.dis(myfloat)" on Fredrik's version and
on your suggested variation... (Hint, it's likely more an instinct for
decent performance instead of an instinct for decent portability

I frankly don't see what "portability" has to do with this. Why would the
location of a reusable static data structure matter ? Python code work
the same way in scripts and modules...

A local variable (i.e. "inside the def") wouldn't be quite so accessible
as a global one...

At least, that's what I inferred the OP meant with his question above.

-Peter