Link : https://pypi.python.org/pypi/engfmt/1.1.0
engfmt – It is a package used to read and write numbers in engineering format.
In engineering format a number generally includes the units if available and uses SI scale factors to indicate the magnitude of the number.
For example:
1ns
1.4204GHz
This package is designed to convert quantities between the various ways in which they are represented. Those ways are:
As a tuple:
For Eg: “1ns” – would be represented as (1e-9, ‘s’).
As a string in conventional formats:
For Eg: “1ns” – would be represented as ‘1e-9 s’ or as ‘0.000000001s’.
– This form is difficult to read for people.
– engfmt treats it more as a format meant for machines rather than people.
As a string in engineering format:
For Eg: “1ns” – would be represented as ‘1ns’.
– This form is difficult to read for machines
– engfmt treats it more as a human readable format.
The Quantity class is provided for converting between these various forms.
- A quantity is the pairing of a real number and units, though the units may be empty.
1.It takes one or two arguments.
Eg: Quantity(1e-9) or Quantity(1e-9, ‘s’)
- The first is taken to be the value, and the second, if given, is taken to be the units.
- The value may be given as a float or as a string.
- The string may be in floating point notation, in scientific notation, or in engineering format and may include the units.
Some examples of the conversions are given below:
For example, any of the following ways can be used to specify 1ns:
As a tuple:
>>> from engfmt import Quantity
>>> period = Quantity(1e-9, ‘s’)
>>> print(period)
1ns
As a string in conventional formats:
>>> period = Quantity(‘0.000000001 s’)
>>> print(period)
1ns
>>> period = Quantity(‘1e-9s’)
>>> print(period)
1ns
As a string in engineering format:
>>> period = Quantity(‘1ns’)
>>> print(period)
1ns
Note: In all cases, the giving the units is optional.
Conversions – Using quantity object you are able to convert it to any representations:
>>> h_line = Quantity(‘1420.405751786 MHz’)
# to converting to tuple with units
>>> h_line.to_tuple()
(1420405751.786, ‘Hz’)
# to converting to string with engineering format
>>> h_line.to_eng()
‘1.4204GHz’
# to converting to string with conventional format
>>> h_line.to_str()
‘1420.405751786e6Hz’
You can also access the value without the units:
# convertig to float
>>> h_line.to_float()
1420405751.786
# converting to a string with conventional format – without units
>>> h_line.to_unitless_eng()
‘1.4204G’
# converting to string with engineering format – without units
>>> h_line.to_unitless_str()
‘1420.405751786e6’
# Get the units only
>>> h_line.units
‘Hz’
There are many other functions also in this package, which is available in the link given.
Some of the functions are given below:
- Quantities As Reals – You can use a quantity in the same way that you can use a real number, meaning that you can use it in expressions and it will evaluate to its real value.
For Example:
>>> period = Quantity(‘1us’)
>> print(period)
1us
- Quantity Class – Quantity class can be used directly, like shortcut functions.
For Example:
>>> from engfmt import Quantity
>>> h_line = Quantity(‘1420.405751786 MHz’)
>>> str(h_line)
‘1.4204GHz’
>>> float(h_line)
1420405751.786
- Physical Constants – The Quantity class also supports a some physical constants.
For Example:
Plank’s constant:
>>> plank = Quantity(‘h’)
>>> print(plank)
662.61e-36J-s
The best thing in this is it also gives Exceptions:
Eg: A ValueError is raised if engfmt cannot convert a string it into a number:
For Example:
>>> try:
... value, units = quant_to_tuple('xxx')
... except ValueError as err:
... print(err)
xxx: not a valid number.
Installation / Usage :
Requires Python2.7 or Python3.3 or better.
1. Use ‘pip install engfmt’ in the cmd prompt to install.
2. By importing the .py file:
- Download the package from the link.
- Copy the engfmt.py from the package and put in the working directory of the python.
- Import the file by from engfmt import* / from engfmt import Quantity.
