## Python internal metric unit conversion function

I'm trying to build a function to do internal metric conversion on a wavelength to frequency conversion program and have been having a hard time getting it to behave properly. It is super slow and will not assign the correct labels to the output. If anyone can help with either a different method of computing this or a reason on why this is happening and any fixes that I cond do that would be amazing!

def convert_SI_l(n): if n in range( int(1e-12),int(9e-11)): return n/0.000000000001, 'pm' else: if n in range(int(1e-10),int(9e-8)): return n/0.000000001 , 'nm' else: if n in range(int(1e-7),int(9e-5)): return n/0.000001, 'um' else: if n in range(int(1e-4),int(9e-3)): return n/0.001, 'mm' else: if n in range(int(0.01), int(0.99)): return n/0.01, 'cm' else: if n in range(1,999): return n/1000, 'm' else: if n in range(1000,299792459): return n/1000, 'km' else: return n , 'm' def convert_SI_f(n): if n in range( 1,999): return n, 'Hz' else: if n in range(1000,999999): return n/1000 , 'kHz' else: if n in range(int(1e6),999999999): return n/1e6, 'MHz' else: if n in range(int(1e9),int(1e13)): return n/1e9, 'GHz' else: return n, 'Hz' c=299792458 i=input("Are we starting with a frequency or a wavelength? ( F / L ): ") #Error statements if i.lower() == ("f"): True else: if not i.lower() == ("l"): print ("Error invalid input") #Cases if i.lower() == ("f"): f = float(input("Please input frequency (in Hz): ")) size_l = c/f print(convert_SI_l(size_l)) if i.lower() == ("l"): l = float(input("Please input wavelength (in meters): ")) size_f = ( l/c) print(convert_SI_f(size_f))

You are using `range()`

in a way that is close to how it is used in natural language, to express a contiguous segment of the real number line, as in *in the range 4.5 to 5.25*. But `range()`

doesn't mean that in Python. It means a bunch of integers. So your floating-point values, even if they are in the *range* you specify, will not occur in the bunch of integers that the `range()`

function generates.

Your first test is

if n in range( int(1e-12),int(9e-11)):

and I am guessing you wrote it like this because what you actually wanted was `range(1e-12, 9e-11)`

but you got `TypeError: 'float' object cannot be interpreted as an integer`

.

But if you do this at the interpreter prompt

>>> range(int(1e-12),int(9e-11)) range(0, 0) >>> list(range(int(1e-12),int(9e-11))) []

you will see it means something quite different to what you obviously expect.

To test if a floating-point number falls in a given *range* do

if lower-bound <= mynumber <= upper-bound:

**[PDF] python-measurement Documentation,** python-measurement Documentation, Release 1.0 Warning: Measurements are stored internally by converting them to a floating-point Note: Python has restrictions on what can be used as a method attribute; if you are not� I ended up writing my own python package for unit conversion and dimensional analysis, but it is not properly packaged for release yet. We are using my unit system in the python bindings for our OpenMM system for GPU accelerated molecular mechanics. You can browse the svn repository of my python units code at: SimTK python units

You don't need ranges and your logic will be more robust if you base it on fixed threshold points that delimit the unit magnitude. This would typically be a unit of one in the given scale.

Here's a generalized approach to all unit scale determination:

SI_Length = [ (1/1000000000000,"pm"), (1/1000000000, "nm"), (1/1000000, "um"), (1/1000, "mm"), (1/100, "cm"), (1, "m"), (1000, "km") ] SI_Frequency = [ (1, "Hz"), (1000,"kHz"), (1000000,"MHz"), (1000000000,"GHz")] def convert(n,units): useFactor,useName = units[0] for factor,name in units: if n >= factor : useFactor,useName = factor,name return (n/useFactor,useName) print(convert(0.0035,SI_Length)) # 3.5 mm print(convert(12332.55,SI_Frequency)) # 12.33255 kHz

Each unit array must be in order of smallest to largest multiplier.

**units � PyPI,** Python support for quantities with units. because a NASA subcontractor ( Lockheed Martin) used Imperial units (pound-seconds) instead of the metric system. Function module MATERIAL_UNIT_CONVERSION will convert material units of measure. It will covert either from an alternate uom to base uom or from base uom to alternate uom. If you need to go from alternate uom to base uom, you will need to call it multiple times. There are other function modules, but this one does not have any restrictions for the

**EDIT:** Actually, `range`

is a function which is generally used in itaration to generate numbers. So, when you write `if n in range(min_value, max_value)`

, this function generates all integers until it finds a match or reach the *max_value*.

The

`range`

type represents an immutable sequence of numbers and is commonly used for looping a specific number of times in`for`

loops.

Instead of writing:

if n in range(int(1e-10),int(9e-8)): return n/0.000000001 , 'nm'

you should write:

if 1e-10 <= n < 9e-8: return n/0.000000001 , 'nm'

Also keep in mind that `range`

only works on integers, not float.

**More EDIT:**

For your specific use case, you can define dictionary of *(value, symbol) pairs, like below:

import collections symbols = collections.OrderedDict( [(1e-12, u'p'), (1e-9, u'n'), (1e-6, u'μ'), (1e-3, u'm'), (1e-2, u'c'), (1e-1, u'd'), (1e0, u''), (1e1, u'da'), (1e2, u'h'), (1e3, u'k'), (1e6, u'M'), (1e9, u'G'), (1e12, u'T')])

The use the `bisect.bisect`

function to find the "insertion" point of your value in that ordered collection. This insertion point can be used to get the simplified value and the SI symbol to use.

For instance:

import bisect def convert_to_si(value): if value < 0: value, symbol = convert_to_si(-value) return -value, symbol elif value > 0: orders = list(symbols.keys()) order_index = bisect.bisect(orders, value / 10.0) order = orders[min(order_index, len(orders) - 1)] return value / order, symbols[order] else: return value, u""

Demonstration:

for value in [1e-12, 3.14e-11, 0, 2, 20, 3e+9]: print(*convert_to_si(value), sep="")

You get:

1.0p 0.0314n 0 2.0 2.0da 3.0G

You can adapt this function to your needs…

**Unit converter in Python,** I want to convert units within the metric system and metric to imperial and vice- versa. I have started with this code and I found this method is slow� Next, we compile and fit the model by specifying the optimizer, training metric, epoch, and batch size. In the last part, we save the model. Note that since we’re using a tf.keras model, we can simply use the .save function by specifying a folder name. Running the script above begins model training for just 3 epochs.

**Units and Quantities (astropy.units) — Astropy v4.0.1,** Unit conversion is done using the to() method, which returns a new Quantity in Syntax, the preferred string formatting syntax in recent versions of python. operations like ordinary numbers, but will deal with unit conversions internally. radian: angular measurement of the ratio between the length on an arc and its radius. In this step-by-step tutorial, you'll learn about the print() function in Python and discover some of its lesser-known features. Avoid common mistakes, take your "hello world" to the next level, and know when to use a better alternative.

**Computing with Units in Python Pint,** It allows conversion between units and even mixing them in the same equation while doing the internal conversion for you, Moreover supports various physical units, If we don't want to convert the unit permenantely we can use method '.to' Pint base units is metric system and can be called as follows:. This was a backwards compatibility workaround to account for the fact that Python originally only supported 8-bit text, and Unicode text was a later addition. In Python 3.x, those implicit conversions are gone - conversions between 8-bit binary data and Unicode text must be explicit, and bytes and string objects will always compare unequal.

**util Module — python-pptx 0.6.18 documentation,** Utility functions and classes. Emu, Cm, Mm, Pt, and Px. Provides properties for converting length values to convenient units. Used internally because PowerPoint stores font size in centipoints. cm � Integer length in English Metric Units. The engine fired but the spacecraft came within 60 km (36 miles) of the planet -- about 100 km closer than planned and about 25 km (15 miles) beneath the level at which the it could function